Smithsonian Institution - United States National Museum - Bulletin 240 (part 1)

Compiler's Notes

Paper 34
Paper 35
Paper 36
Paper 37
Paper 38
Paper 39
Paper 40
Paper 41
Paper 42
Paper 43
Paper 44

SMITHSONIAN INSTITUTION

UNITED STATES NATIONAL MUSEUM

BULLETIN 240

SMITHSONIAN PRESS

MUSEUM OF HISTORY AND TECHNOLOGY

Contributions
From the
Museum
of History and
Technology

Papers 34-44
On Science and Technology

SMITHSONIAN INSTITUTION · WASHINGTON, D.C. 1966

Publications of the United States National Museum

The scholarly and scientific publications of the United States National Museum include two series, Proceedings of the United States National Museum and United States National Museum Bulletin.

In these series, the Museum publishes original articles and monographs dealing with the collections and work of its constituent museums—The Museum of Natural History and the Museum of History and Technology—setting forth newly acquired facts in the fields of anthropology, biology, history, geology, and technology. Copies of each publication are distributed to libraries, to cultural and scientific organizations, and to specialists and others interested in the different subjects.

The Proceedings, begun in 1878, are intended for the publication, in separate form, of shorter papers from the Museum of Natural History. These are gathered in volumes, octavo in size, with the publication date of each paper recorded in the table of contents of the volume.

In the Bulletin series, the first of which was issued in 1875, appear longer, separate publications consisting of monographs (occasionally in several parts) and volumes in which are collected works on related subjects. Bulletins are either octavo or quarto in size, depending on the needs of the presentation. Since 1902 papers relating to the botanical collections of the Museum of Natural History have been published in the Bulletin series under the heading Contributions from the United States National Herbarium, and since 1959, in Bulletins titled “Contributions from the Museum of History and Technology,” have been gathered shorter papers relating to the collections and research of that Museum.

The present collection of Contributions, Papers 34-44, comprises Bulletin 240. Each of these papers has been previously published in separate form. The year of publication is shown on the last page of each paper.

Frank A. Taylor
Director, United States National Museum

Papers

Page

34. The 1893 Duryea Automobile
Don H. Berkebile

35. The Borghesi Astronomical Clock
Silvio A. Bedini

36. The Engineering Contributions of Wendel Bollman
Robert M. Vogel

37. Screw-Thread Cutting by the Master Screw Method Since 1480
Edwin A. Battison

38. The Earliest Electromagnetic Instruments
Robert A. Chipman

39. Fulton’s “Steam Battery”: Blockship and Catamaran
Howard I. Chapelle

40. History of Phosphorus
Eduard Farber

41. Tunnel Engineering—A Museum Treatment
Robert M. Vogel

42. The “Pioneer”: Light Passenger Locomotive of 1851
John H. White

43. History of the Division of Medical Sciences
Sami Hamarneh

44. Development of Gravity Pendulums in the 19th Century
Victor F. Lenzen and Robert P. Multhauf

Contributions from
The Museum of History and Technology:
Paper 34

The 1893 Duryea Automobile
In the Museum of History and Technology

Don H. Berkebile

EARLY AUTOMOTIVE EXPERIENCE 5

CONSTRUCTION BEGINS 6

DESCRIPTION OF THE AUTOMOBILE 16

INDEX

Figure 1.—Duryea automobile in the Museum of History and Technology, from an 1897 photograph. The gear-sprockets were already missing when this was taken, and the chain lies loosely on the pinion. Shown at the right, the Duryea vehicle following the recent restoration (Smithsonian photo 34183).

Don H. Berkebile

THE 1893 DURYEA AUTOMOBILE

In the Museum of History and Technology

During the last decade of the nineteenth century a number of American engineers and mechanics were working diligently to develop a practical self-propelled vehicle employing an internal-combustion engine as the motive force. Among these men were Charles and Frank Duryea, who began work on this type of vehicle about 1892. This carriage was operated on the streets of Springfield, Massachusetts, in 1893, where its trials were noted in the newspapers. Now preserved in the Museum of History and Technology, it is a prized exhibit in the collection of early automobiles.

It is the purpose of this paper to present some of the facts discovered during the restoration of the vehicle, to show the problems that faced its builders, and to describe their solutions. An attempt also has been made to correlate all this information with reports of the now almost legendary day-to-day experiences of the Duryeas, as published by the brothers in various booklets, and as related by Frank Duryea during two interviews, recorded on tape in 1956 and 1957, while he was visiting the Smithsonian.

The Author: Don H. Berkebile is on the staff of the Museum of History and Technology, in the Smithsonian Institution's United States National Museum.

Of the numerous American automotive pioneers, perhaps among the best known are Charles and Frank Duryea. Beginning their work of automobile building in Springfield, Massachusetts, and after much rebuilding, they constructed their first successful vehicle in 1892 and 1893. No sooner was this finished than Frank, working alone, began work on a second vehicle having a two-cylinder engine. With this automobile, sufficient capital was attracted in 1895 to form the Duryea Motor Wagon Company in which both brothers were among the stockholders and directors. A short time after the formation of the company this second automobile was entered by the company in the Chicago Times-Herald automobile race on Thanksgiving Day, November 28, 1895, where Frank Duryea won a victory over the other five contestants—two electric automobiles and three Benz machines imported from Germany.

In the year following this victory Frank, as engineer in charge of design and construction, completed the plans begun earlier for a more powerful automobile. During 1896 the company turned out thirteen identical automobiles, the first example of mass production in American automotive history. Even while these cars were under construction Frank was planning a lighter vehicle, one of which was completed in October of 1896. This machine was driven to another victory by Frank Duryea on November 14, 1896, when he competed once again with European-built cars in the Liberty-Day Run from London to Brighton. The decision to race and demonstrate their autos abroad was the result of the company's desire to interest foreign capital, yet Frank later felt they might better have used their time and money by concentrating on building cars and selling them to the local market. Subsequently, in the fall of 1898, Frank arranged for the sale of his and Charles' interest in the company, and thereafter the brothers pursued separate careers.

Figure 2.—Workmen in the Duryea factory in Springfield, Mass.,
working on some of the thirteen 1896 motor wagons. (Smithsonian photo 44062.)

Frank, in 1901, entered into a contract with the J. Stevens Arms and Tool Company, of Chicopee Falls, Massachusetts, which built automobiles under his supervision. This association led in 1904 to the formation of the Stevens-Duryea Company, of which Irving Page was president and Frank Duryea was vice president and chief engineer. This company produced during its 10-year existence a number of popular and well-known models, among them a light six known as the Model U, in 1907; a larger 4-cylinder called the Model X, in 1908; and a larger six, the Model Y, in 1909. In 1914 when Stevens withdrew from the company, Frank obtained control. The following year he sold the plants and machinery, liquidated the company, and, due to ill health, retired.

Charles, in the meantime, located in Reading, Pennsylvania, where he built autos under the name of the Duryea Power Company. Here, and later in Philadelphia under the name of the Duryea Motor Corporation and other corporate names, he continued for a number of years to build automobiles, vacuum cleaners and other mechanical devices. Until the time of his death in 1938, he practiced as a consulting engineer.

Figure 3.—Admittance card of C. E. Duryea to the U.S. Patent Office, 1887.
(Gift of Rhea Duryea Johnson.)

Early Automotive Experience

Figure 4.—Charles E. Duryea, about 1894,
as drawn by George Giguere from a photograph.
(Smithsonian photo 48335-A.)

Born in 1861 near Canton, Illinois, Charles E. Duryea had learned the trade of a mechanic following his graduation from high school, and subsequently turned his interests to bicycle repair. He and his brother James Frank, eight years younger, eventually left Illinois and moved to Washington D.C., where they were employed in the bicycle shop of H. S. Owen, one of that city's leading bicycle dealers and importers. While in Washington, Charles became a regular reader of the Patent Office Gazette, an act which undoubtedly influenced his later work with automobiles. A short time later, probably in 1889, Charles contracted with a firm in Rockaway, New Jersey, to construct bicycles for him, but their failure to make delivery as promised caused him to go to Chicopee, Massachusetts, where he contracted with the Ames Manufacturing Company to do his work. Moving there in 1890, he obtained for his brother a position as toolmaker with the Ames Company. Thus, Frank Duryea, as he was later known, also became located in Chicopee, a northern suburb of Springfield.

During the summer, 1891, Charles found the bicycle business left him some spare time, and the gasoline-powered carriages he had read of earlier came constantly into his mind in these periods of idleness. He and Frank studied several books on gasoline engines, among them one by an English writer (title and author now unknown); this described the Otto 4-stroke cycle as now used. Some engineers, however, were concerned because this engine, on the completion of the exhaust stroke, had not entirely evacuated all of the products of combustion. The Atkinson engine, patented in 1887, was one of the attempts to solve this as well as several other problems, thus creating a more efficient cycle. This engine was designed so that the exhaust stroke carried the piston all the way to the head of the engine, while the compression stroke only moved the piston far enough to sufficiently compress the mixture. The unusual linkage necessary to create these unequal strokes in the Atkinson engine made it seem impractical for a carriage engine, where compactness was desired.

Figure 5.—Advertisement of Duryea bicycle company,
Scientific American, September 9, 1893.

Going to Hartford, Connecticut, possibly on business relating to his bicycle work, Charles visited the Hartford Machine Screw Company where the Daimler-type engine was being produced, but after examining it he felt it was too heavy and clumsy for his purpose. Also in Hartford he talked over the problem of a satisfactory engine with C. E. Hawley, an employee of the Pope Manufacturing Company, makers of the Columbia bicycle. Hawley, searching for a way to construct an engine that would perform in a manner similar to the Atkinson, yet would have the lightness and compactness necessary for a carriage engine, suggested an idea that Charles believed had some merit. This idea, involving the use of what the Duryeas later called a "free piston," was eventually to be incorporated in their first engine.

Figure 6.—J. Frank Duryea, about 1894,
as drawn by George Giguere from a photograph.
(Smithsonian photo 48335.)

Construction Begins

Back in Chicopee again, Charles began planning his first horseless carriage. Frank later stated that they leaned heavily on the Benz patents in their work; but while the later engine and transmission show evidence of this, only the Benz manner of placing the engine and the flywheel seem to have been employed in the original Duryea plan. Charles reversed the engine so that the flywheel was to the front, rather than to the rear as in the Benz patent, but made use of Benz' vertical crankshaft so that the flywheel rotated in a horizontal plane. Previously most engines had used vertical flywheels; Benz, believing that this practice would cause difficulty in steering a propelled carriage, explained his reason for changing this feature in his U.S. patent 385087, issued June 26, 1888:

In motors hitherto used the fly-wheels have been attached to a horizontal shaft or axle, and have thus been made to revolve in a vertical plane, since the horizontal shaft is best adapted to the transmission of power. If, however, in this case we should use a heavy rotating mass, corresponding to the power employed and revolving rapidly in a vertical plane, the power to manage the vehicle or boat would become very much lessened, as the flywheel continues to revolve in its plane. I therefore so design the apparatus that its crank shaft x has a vertical position and its fly-wheel y revolves in a horizontal plane…. By this means the vehicle is not only easily controlled, but also the greatest safety is attained against capsizing.

To the Duryea plan, Benz may also have contributed the idea for positioning the countershaft, though its location is sufficiently obvious that Charles may have had no need for copying Benz. Charles wisely differed from Benz in placing the flywheel forward, thus eliminating the need for the long driving belt of the Benz carriage. Yet he did reject the bevel gears used by Benz, which might well have been retained, as Frank was later to prove by designing a workable transmission that incorporated such bevel gears. The initial plan, as conceived by Charles, also included the details of the axles, steering gear, countershaft with its friction-drum, the 2-piece angle-iron frame upon which the countershaft bearings were mounted, and the free piston engine with its ignition tube, since hot-tube ignition was to be employed. No provision was made, however, for a burner to heat the tube; nor had a carburetor been designed, though it had been decided not to use a surface tank carburetor. The plans called for no muffler or starting arrangement. Many engines of the period were started simply by turning the flywheel with the hands, and Charles felt this method was sufficient for his carriage.

Figure 7.—Drawing showing principle of the Atkinson engine; this feature
is what the Duryeas were trying to achieve with their free-piston engine, by
substituting the free piston for the unusual linkage of the Atkinson.
(Smithsonian photo H3263-A.)

Figure 8.—Drawing of 1885 Benz engine, showing
similarity in general appearance to Duryea engine. From
Karl Benz und sein Lebenswerk, Stuttgart, 1953.
(Daimler-Benz Company publication.)

The Ames plant customarily had a summer shutdown during August; thus, during August of 1891 Charles and Frank had access to a nearly empty plant in which they could carry on experiments and make up working drawings of the proposed vehicle. It cannot now be conclusively stated whether any parts were made for the car during August or the remainder of the year. It is more likely that the brothers attempted to complete a set of drawings. Frank Harrington, chief draftsman at Ames, may have helped out at this time; from Charles' statement of April 14, 1937, it is learned that he did prepare drawings during 1892.

Figure 9.—Illustration from U.S. patent 385087,
issued to Carl Benz, showing the horizontal plane
of the flywheel, a feature utilized by the Duryeas in their machine.

The first contemporary record of any work on vehicles is a bill, dated January 21, 1892, for a drawing made by George W. Howard & Company. This drawing was made in the fall of 1891 by Charles A. Bartlett, a member of the Howard firm and a neighbor of Charles Duryea, according to a statement by Charles in the Automobile Trade Journal of Jan. 10, 1925. He was then also of the opinion that this drawing may not have had anything to do with the carriage they were about to assemble, but a notation found by Charles at a later date has led him to believe that it possibly concerned a business type vehicle he had discussed with an unidentified Mr. Snow.

By early 1892 Charles needed capital to finance his venture, an old carriage to attach his inventions to, a place to work, and a mechanic to do the work. On March 26, he stopped by the Smith Carriage Company and looked over a selection of used buggies and phaetons. He finally decided on a rather well-used ladies' phaeton which he purchased for $70. The leather dash was in so deplorable a state it would have to be recovered before the carriage went onto the road, and the leather fenders it once possessed had previously been removed; yet the upholstery appeared to be in satisfactory condition, and the candle lamps were intact.

Figure 10.—Phantom illustration of Benz' first automobile.
(From Carl Benz, Father of the Automobile Industry, by L. M. Fanning, New York, 1955.)

Two days later, Charles was able to interest Erwin F. Markham, of Springfield, sufficiently to obtain his financial aid in the project. A contract was drawn up between the two men, which stated that Mr. Markham was to put up $1000 for which he received a five-tenths share of the venture. When the $1000 had been used, he then had the option to continue his aid until the project had been carried to a successful climax, and retain his half share, or to refuse further funds and relinquish four of his five-tenths interest in the business. Had he eventually chosen the latter, Charles would obviously have had to seek assistance elsewhere.

Figure 11.—The Howard & Co. bill showing the first work performed
toward a motor vehicle. While this may not refer specifically
to the machine now in the museum, it is evidence of early work.

Figure 12.—The shop of John Russell & Sons.
It was on the second floor of this building that
Charles and Frank Duryea built their first motor vehicle.
(Courtesy of the Springfield Union.)

That same day, March 28, Charles found working space and machinery available at John W. Russell & Sons Company in Springfield. The Russells had recently completed a large government order of shells for the famous dynamite guns later used on board the cruiser Vesuvius in the Spanish-American War, and this left an entire second floor, approximately 35 × 85 feet, virtually unoccupied, according to an affidavit of William J. Russell of April 30, 1926. Now ready to begin the actual work, Charles hired his brother Frank to start construction. Frank started about the first of April, receiving a raise of about 10 percent over the salary he had received at Ames. Before the vehicle was completed a number of other men performed work on some of the parts, among them William Deats who had been hired by Charles primarily to work on bicycles in the same area, but who occasionally assisted on the carriage. Russell Company records show time charged against Charles Duryea by six other Russell employees: W. J. Russell, P. Colgan, C. E. Merrick, T. Shea, L. J. Parmelee, and A. A. Poissant.

Figure 13.—J. Frank Duryea looking over the Russell shop lathe
on which he turned parts for the first Duryea vehicle.
Photo taken about 1944. (Courtesy of the Springfield Union.)

It is Frank Duryea's remembrance that he started work on Monday, April 4. He first removed the body, with its springs, and placed it on a pair of wooden horses where it remained until the summer of the following year. The next step was to remove the rear axle and take it to a blacksmith shop where the old axle spindles were cut off and welded to a new drop-center axle. Following this the front axle spindles were removed, the ends of the axle slotted, and a webbed, C-shaped piece carrying the kingpin bearings was fitted into each slot, braced from underneath by short brackets which were riveted and brazed in place. The old spindles then were welded to the center of offset kingpins which in turn were mounted in their bearings in a manner similar to that in which the frame of the Columbia high-wheeled bicycle was mounted in its fork. Arms welded to the lower end of the kingpins were connected by the tie rods to an arm on the lower end of the vertical steering column, located on the center of the axle.

Figure 14.—A portion of the Russell shop
records showing charges made against
Charles Duryea during 1893-1894.

While work on the running gear advanced, some progress was made in the construction of the engine. Patterns for the castings were fabricated, most of them by Charles Marshall on Taylor Street, and castings were poured. The body or main casting of the engine resembled a length of cast-iron pipe: it had no bosses or lugs cast on, nor any water jacket, for they thought the engine would be kept cool merely by being placed in the open air. The front end of the engine was secured to the vehicle by four bolts which passed through the halves of the bearings and onto four projections on the open end of the engine. As the crankshaft of this engine was retained in constructing the present engine, it is logical to assume that the bearings were the same also. The head was cast as a thick disc, with both intake and exhaust valves located therein, and was bolted onto the flanged head end of the engine.

Inside the cylinder was the strange arrangement previously suggested by C. E. Hawley. To the connecting rod was attached a rather ordinary ringed piston, over which was fitted a free, ringless piston, machined to fit closely the cylinder bore. This floating piston could move freely a distance equal to the compression space. The intention was that on the intake stroke, suction would open the intake valve, which had no positive opening arrangement, and draw in the mixture which then was compressed as in a regular Otto engine. Fired by the hot-tube ignition system, the force of the explosion would drive both pistons down, forcing the outer one tight against the head of the smaller one, and at the end of the stroke the longer wall of the outer piston would strike an arm projecting into the cylinder near the open end, moving forward the exhaust valve rod to which the arm was attached, thus pushing open the valve in the head. On the exhaust stroke the unrestrained outer piston moved all the way to the head, expelling all of the products of combustion and pushing the exhaust valve shut again. With a bore of four inches or less, this engine, Charles believed, should develop about three horsepower and run at a speed between 350 to 400 revolutions per minute.

As no ignition system had yet been provided, they prepared a 4½-inch length of one-quarter inch iron pipe, closed at one end, and screwed the open end into the head. Heating this tube with an alcohol burner would cause ignition of the mixture when a portion of it was forced into the heated tube toward the end of the compression stroke. No attempt was made at this time to use the electrical make-and-break circuit used in their second engine, as the free piston would have wrecked the igniter parts on the exhaust stroke, and the push rod located on the end of the piston would have prevented the piston from closing the exhaust valve.

After keying the flywheel to the lower end of the crankshaft, Charles and Frank decided to make an attempt to run the engine. Carrying it into a back room, probably during July or August, 1892, they blocked it up on horses. A carburetor had not yet been constructed, so they attempted to start the engine by spinning the flywheel by hand, at the same time spraying gasoline through the intake valve with a perfume atomizer previously purchased at a drugstore in the Massasoit House. Repeated efforts of the two men to start the engine resulted in failure.

Figure 15.—Conjectural drawing of the free-piston engine used in the Museum vehicle prior to the present engine. (Drawing by A. A. Balunek.)

In the belief that the defects, whatever they might be, could be remedied after the engine was installed, the Duryeas went ahead and mounted the engine in the carriage. To do this they shortened the original reach of the carriage, allowing the engine itself to become the rear continuation of the reach. The four ears on the front, or open end of the engine, were bolted to the centrally located frame, with the bearing blocks in between. This frame, the same one now in the vehicle, was constructed of two pieces of angle iron, riveted and brazed together. Greater rigidity was obtained by a number of half-inch iron rods running from the frame to both front and rear axles. Because of the absence of any mounting brackets on the engine casting itself, a wooden block with a trough on top to receive the body of the engine was fitted between the engine and the axle, while two U-shaped rods secured it with clip bars and nuts underneath.

Beneath the flywheel was mounted the friction transmission of Charles' design. This consisted of a large drum, perhaps 12 inches in diameter, equal in length to the diameter of the flywheel and keyed to a shaft directly under the center of the crankshaft and parallel to the axles. (Diameter of drum estimated by examination of existing features.) In view of the four projections of the frame extending downward and just in front of the jackshaft position, it is likely that these supported the four jackshaft bearings. Being a bicycle manufacturer, Charles saw the need for a differential or balance gear. Accordingly, he purchased from the Pope Manufacturing Company a very light unit of the type formerly used on Columbia tricycles, and installed it somewhere on the jackshaft. A small sprocket on each end of the shaft carried a chain from the larger sprockets clamped to the spokes of each rear wheel. The lower surface of the flywheel had been machined so as to form a friction disc, with a one-quarter inch depression 3 inches in diameter turned in the center. The drum was positioned so that its upper surface was one-quarter inch below the face of the flywheel. Hanging loosely around the drum was an endless belt, one and one-half inches wide, first made of rather soft rubber packing material. The belt lay on the drum surface between the fingers of a shipper fork. While it lay under the 3-inch depression in the center of the flywheel, the belt and the drum were at rest, but when it was moved away from that depression the belt wedged itself tightly between the drum and flywheel, the resulting friction causing the drum to turn and setting the vehicle into motion. The farther the belt was moved toward the outer edge of the wheel, the faster the drum and the vehicle moved.

In September 1892, Charles, who had contracted with a Peoria, Illinois, firm to have bicycle parts manufactured, decided to move to that city. Departing on the 22d of September, he did not return to Springfield for over two years, and thus was not able to participate in the completion and testing of the carriage. At the time of his departure several units on the carriage were incomplete. A carburetor had not been built, nor had a satisfactory burner or belt-shifting device. Charles had experimented with various shifting levers just before leaving Springfield: however, as he reported later, he did not succeed in designing a workable mechanism. Frank Duryea, now left to finish the work unassisted, continued the experiments with the belt shifter. He finally worked out a fork mounted on a carriage that was supported by two rods, each of which slid in two bearings. Although the short distance between the two bearings caused the shifter carriage to bind occasionally, the device was thought to be sufficient and was installed just in front of the frame. Connected to a system of cables, arms, and rods, possibly similar to the present cam-bar shifter, the shipper-fork carriage was moved from side to side by raising or lowering the tiller.

Figure 16.—Drawing of the carburetor used on both Duryea engines, 1893-1894,
showing sight feed on left and choke mechanism on right. (Smithsonian photo 13455.)

Turning now to an efficient burner for heating the ignition tube, Frank started with an ordinary wick-type kerosene lamp with a small metal tank. Wishing to use gasoline in the lamp, he found it necessary to fabricate a number of burner units before he found a type that gave him a clean blue flame. He then found the flame to be very sensitive to drafts and easily extinguished, and devised a small shield or chimney to afford it some protection.

Early in October, while still working with the burner, Frank developed a severe headache. He felt the fumes of the lamp had probably caused it, and went to his room in the home of a Mr. and Mrs. Patrick on Front Street in Chicopee. After he noticed no improvement, a doctor's examination showed he had typhoid fever, and on October 5 he was admitted to the Springfield Hospital. Here he remained for one month, being discharged on November 5. Returning to his room he was informed that because of the fear that he might be a typhoid carrier, the Patricks preferred him to find other lodgings. He readily accepted the invitation of Mr. and Mrs. D. H. Nesbitt of Chicopee to take a room with them. After several weeks recuperation in their home, he left Springfield to visit his mother in Wyoming, Illinois.

After a restful visit at home Frank Duryea returned to Springfield and finished the work on his burner. Now only the lack of a carburetor prevented a trial of the vehicle. He recalls that he studied several gasoline-engine catalogs and in one of them, a Fairbanks catalog he believes, he saw a design that seemed to suit his needs. He decided to simplify the construction and operation of his carburetor and had a small bronze casting made to form the body of it. Inside was a gasoline chamber with two tapped openings, one to receive a pipe from the 2-gallon gasoline tank mounted above the engine, the other taking a pipe to the overflow tank underneath the engine, thus maintaining the gasoline level without the use of a float valve. This latter tank had a hand pump on one end so that the overflow gasoline could at times be pumped again into the main tank. Gasoline passed from the carburetor chamber through a needle valve, adjusted by a knob on top, then through a tiny tube that entered the pipe leading to the intake valve. It is not certain whether this intake pipe was at first fitted with the choke arrangement later used with the second engine.

Frank, hoping at last to be rewarded for his efforts by the sound of explosions from the engine, was ready to give the carriage an indoor trial. Standing astraddle of the reach and facing to the rear, he spun the flywheel with both hands, taking care not to get his hands caught between the wheel and the frame. His efforts were in vain, as there was complete failure to obtain ignition. He then made a new ignition tube, nearly twice as long as the original 4-½-inch tube, and turned down its wall as thin as he thought safety allowed. The thinner wall did not conduct the heat off so rapidly and thus kept the tube hot enough to permit ignition. After this slight change, he was able to get a few occasional explosions but he does not now believe that the engine ever operated continuously. Each explosion was accompanied by a loud knock, due, undoubtedly, to the movement of the free piston. Had the engine operated continuously, it is likely that the action of the free piston would have shortly wrecked the engine. Further efforts appeared unwarranted until alterations could be made.

Figure 17.—Letter explaining the circuit breaker spring and the brass projection on top of the ignition chamber.
Mr. Mitman was, at the time, curator of engineering in the U.S. National Museum.
View Larger Image of Letter Text of Letter

The two pistons were first pinned together into a single unit which was probably ringless, since it is believed the walls of the outer piston were too thin to admit rings. Because the piston no longer struck the exhaust valve, a short rod had to be screwed into the pistonhead; this pushed the valve shut at the completion of the exhaust stroke. The remaining problem, the opening of the exhaust valve, was solved by screwing a device to the side of the cylinder which operated from the sidewise motion of the connecting rod. This device shifted a small spacer between the piston and the striker arm of the exhaust-valve rod, permitting the piston to push open the exhaust valve. On alternating strokes the spacer shifted back out of the cylinder; therefore, no contact was made between piston and striker arm. Sometime in February 1893, the altered engine was successfully started.

At last the transmission could be tested. Will Russell had come upstairs to watch the trial, and according to a statement by him, given April 30, 1926, Frank, standing to the right of the engine and behind the rear axle, reached forward and with the combination tiller-belt-shifter, moved the belt into driving position. The carriage started forward, but as it approached the wall of the building Frank discovered that he could not get the belt back into the neutral position. In desperation, he grasped the rear axle with both hands and was dragged a short distance, attempting to stop the machine, before it struck the wall. He had, however, sufficiently retarded it so that no damage was done.

This short trial demonstrated some of the weaknesses in the friction transmission. Since the speed of the surface of the flywheel, in feet per second, increased in proportion to the distance of the point of contact from the center, the outer edge of the belt attempted to run faster than the inner edge. This conflict of forces not only put an undue load on the motor causing a great loss of power, but it also created a tendency for the belt to work towards the outer edge of the flywheel. Conversely, when the operator desired to return the belt to neutral, it strongly resisted any efforts to slide it toward the center of the wheel, as Frank had learned from the wall-bumping incident. Furthermore, the rubber belt on the friction drum had worn so badly that it had to be replaced at least once during the brief experiments.

Figure 18.—Ignition chamber, switch,
and breaker contacts of the present Duryea engine.

At this point, Frank and Markham felt that the carriage was anything but satisfactory. While they were trying to decide what steps should be taken next, Frank added one last improvement to the engine. Fearing that the uncooled cylinder might suffer damage from the excessive heat, he constructed a copper water jacket in two halves, drew them together around the cylinder with clamping rings and soldered the seams. Asbestos packing sealed the end joints where the jacket contacted the cylinder. Thinking back, Frank does not recall that he ever used a water tank with this engine, though he does remember adding water through the upper jacket opening. The engine was run only for a few brief periods following this addition.

Obviously this collection of patchwork could not fulfill their needs for an engine. First, it would be next to impossible to start if the body was placed on the running gear, as the flywheel then would be practically inaccessible. The absence of rings on the piston caused a further loss of power to the already overloaded engine. The flywheel was too light. The absence of any form of governor left the operator with no control over the engine speed. Ignition was poor, partly owing to the hot-tube arrangement, and partly to the excessive distance between the engine and the carburetor. Frank wrote his brother Charles on February 6 that in his opinion the mixing chamber was so far from the engine that the gasoline could not be drawn into the cylinder as liquid, and it was too cold to vaporize and go in as gas. Thus he had difficulty in getting the engine started. When it did start the explosions were unmuffled. Less important to him than these defects, however, was the awkward and unsightly wooden engine mount.

Description of the Automobile

Sometime in the early part of March, Frank convinced Markham that he could construct a new and practical engine, using only previously tried mechanical principles. Drawing up new plans for this engine, he took them to Charles Marshall who began work on the patterns for the new engine castings. After the patterns had been delivered to the foundry, Frank left Springfield for a short vacation in Groton, Connecticut, where he visited with his fiancée. On May 17, 1893, several weeks after his return to Springfield, they were married.

The engine castings were undoubtedly received from the foundry prior to Frank Duryea's marriage, and the work of machining and assembling the parts went on through the spring and summer. This engine, still on the carriage in the Museum of History and Technology, is cased with a water jacket, and has bases on top to support the front and rear bearings of the starting crankshaft, and a base with port on the upper right side where the exhaust-valve housing was to be bolted. On the underside are two flanges, forming a base for seating the engine on the axle. A separate combustion chamber is cast and bolted to the head. Inside this chamber are located the igniter parts of Frank's electric ignition system. The fixed part, an insulated electrode, is screwed into the right side of the chamber and is connected with the ignition switch outside, to which one of the ignition wires is attached. A breaker arm inside is pinned to a small shaft extending through the top of the chamber. Around the breaker-arm shaft is a small coil spring (originally a spiral spring, according to the letter of Charles Duryea shown in fig. 17), anchored below to a thin brass finger extending toward the right side of the car, and above to a nut screwed tightly onto the shaft. This nut is also the terminal for the other ignition wire. The action of the spring keeps the breaker arm and the electrode in constant contact until the push rod on the end of the piston strikes the arm and separates the two parts. Breaking contact then produces the ignition spark. Since the mechanism would spark at the end of both the exhaust and compression strokes, the battery current is conserved by a contact strip, on the underside of the larger exhaust-valve gear, by means of which the flow of current is cut off during the greater part of the cycle.

On the left side of the combustion chamber is bolted the housing containing the tiny intake valve. A comparatively weak spring seats this valve in order that the suction created by the piston can easily pull it open. Clamped onto the valve housing is the intake pipe, enclosing the choke and carrying the carburetor on its forward side. The choke consists of two discs which block the pipe, each with four holes at the edges and one in the center. Turning one disc by means of a small handle outside, so that the four outer holes cannot coincide with those in the other disc, decreases the flow of air and causes all air to rush through the center hole, where the tiny carburetor tube passes through. The present carburetor was transferred over from the first engine. When Frank later installed the engine on the carriage he noticed the close proximity of the intake pipe to the open end of the muffler. Believing that the fumes might choke the engine, he attached a long sheet-metal tube to the intake pipe so that fresh air would be drawn in from a point farther forward on the vehicle.

Moving to the right side of the engine brings the exhaust-valve assembly into view. This valve is contained in a casting bolted over the exhaust port in the side of the cylinder, and from the casting a pipe leads to the muffler underneath. The valve is pushed open by a rod connected to a crank which is pinned to the lower end of a shaft carrying an iron gear on top. This gear is in mesh with a fiber gear, keyed to the upper end of the crankshaft, with half the number of teeth. This ratio permits the opening of the exhaust valve on every other revolution.

The crankshaft of the first engine was retained for the new engine, thus giving the two engines the same stroke of 5-⅜ inches, but the bore was increased slightly to 4⅜ inches. With this larger bore and with the engine speed increased to 500 rpm, Frank rated this engine at 4 hp. A heavier flywheel, with a governor resting in the upper recess, was pressed onto the crankshaft. As the operator of the vehicle had no control over the carburetor once he climbed into the seat, this governor was necessary to maintain regular engine speed. Its function was to move a slide on the exhaust-valve unit to prevent the valve from closing. Thus the engine, with the suction broken, could not draw a charge on the next revolution. During the recent restoration of this carriage it was found that while most parts are still intact, nearly all of the governor parts are missing. A description of them must therefore be based on the recollections of Frank Duryea, along with certain evidences seen on the engine.

Figure 19.—Under side of exhaust valve mechanism showing electrical contacts that give spark only on every other revolution.

Just on top of the flywheel, and surrounding the crankshaft, rest two rings, 3⅞ inches in diameter. Into the opposing surfaces of these rings are cut a series of small inclined planes, appertinent to each other. On the outer circumference of the upper ring two pins pass through a pair of lugs mounted in the flywheel, causing the ring to rotate with the flywheel, yet permitting vertical movement. Underneath, the other ring is allowed to turn slightly when, by means of two connecting links, the arms of the governor push against them. These two arms, each constructed like a right angle and pivoted at the apex, are arranged directly opposite each other far out in the flywheel recess. As a weight on one angle of the arm presses outward by centrifugal force against a spring, the other angle presses inward against the connecting link mentioned above. The turning of the lower set of inclined planes against the fixed set above raises the upper ring and the fork resting on it. The upward movement of this fork, which is a continuation of an arm pivoted to a bracket midway between the crankshaft and the slide carrying the exhaust valve stop, causes the other end of the arm to drop, pulling the slide down with it. In this manner the closing of the exhaust valve is blocked, preventing the intake of the next charge, and therefore the engine misses one or more explosions until it slows to its normal speed.

A starting shaft is mounted above the engine casting by a cast-iron bracket on either end. The front end of the shaft has a bevel gear which is held by a coil spring behind the front bracket, just out of contact with a bevel gear pressed onto the upper end of the crankshaft. The short rear portion of the shaft is a tube which slides over the main shaft. Fitting the removable handcrank to the squared end of the hollow shaft and turning the crank clockwise, will advance the forward section of shaft through the medium of a pair of inclined collars. With the bevel gears now engaged the engine may be cranked. When ignition begins, the inclined collars slide back down each other's surfaces, the shaft is again shortened, and its bevel gear springs free of the one on the crankshaft.

Figure 20.—Piston and connecting rod of second engine. Screw on rod is where oil is poured into connecting rod to lubricate wrist pin and crankshaft.

While Frank worked on his engine, he realized that certain parts of the old running gear would need to be altered or replaced. In view of the heavier and more powerful engine, he felt the old wheels, probably having compressed band hubs, were inadequate. He procured a set of new, heavier wheels with Warner-type, cast-iron reinforced hubs. The angle iron frame, apparently sturdy enough to carry the added weight, was retained, but it was decided to install a heavier rear axle. The front axle assembly was at first allowed to remain unchanged, as was the steering apparatus. A short time later when the engine and friction transmission were bolted in place on the running gear, Frank saw that the rigidity of the framework had an undesirable effect. When the vehicle passed over any unevenness in the shop floor, the framework was distorted and caused the jackshaft bearings to bind tightly enough on the shaft to prevent its being turned by hand. In order to provide the 3-point suspension necessary to eliminate this distortion, Frank attached the forward parts of the framework to an extra wooden spring bar, installing between this bar and the front axle a vertical fifth wheel of the type ordinarily used in a horizontal position in any light carriage.

Frank next calculated that with the faster running engine the speed of the vehicle would be about 15 miles an hour, too much for the heavily loaded wheels. As he intended to make use of the original transmission, he decided to decrease the speed by increasing the size of the friction drum. He accomplished this by sliding a heavy fiber tube over the original drum, bringing its diameter to approximately 14 inches. The original shipper fork carriage was improved by separating the original bearings to a greater distance, and eliminating one of the two bearings on one end. This permitted a smooth and free operation of the small sliding carriage.

In August 1893, possibly as a result of indoor experiments, Frank discovered that the chains running from the small 5-tooth jackshaft sprockets to the large, bronze, wheel sprockets were tight at some times and loose at others. This caused considerable unnecessary noise. The difficulty apparently was the result of the sprockets being cast and not machined. The patternmaker had said he believed he could make the pattern accurately enough so that no machining of the castings would be necessary. Nice castings were produced, but "these sprockets were the reason why an unusual construction was put on the crankshaft [meaning jackshaft]," explained Frank Duryea during an interview at the National Museum on November 9, 1956. Elaborating further, in reply to the queries of E. A. Battison, of the Museum's division of engineering, Duryea told of the problem and the solution when he explained that the sprockets had places where the shrinkage was not even. The hot metal, contracting as it cooled, did not seem to contract uniformly, creating slightly unequal distances between teeth. This resulted in the chain hanging quite loose in some places and in others the tightness prevented adjustment. He contacted Will Russell, foreman of the Russell shop, where the automobile was made, and Russell showed him a device, built by George Warwick, who had made the Warwick bicycle. It was an internal-cut gear, according to Duryea's description, with sprocket teeth on its periphery. With sprockets outside and normal teeth inside, the wheels were about 6 inches in diameter, externally.

These little internal-gear sprockets were hung on double-shrouded pinions secured to each end of the jackshaft. A solid disc or housing fitted against both ends of the pinion to prevent the internal gear from working off sideways. Duryea explained the function of these unique little parts: "as soon as tension came on that ring gear that we talked about, it not only tightened the chain hanging on this sprocket on the upper side, but it tightened it on both sides. [The sprocket] rocks right out: both sides of the chain are tight."

This feature is one rarely encountered elsewhere, and Duryea, later in the interview said, "To tell you the truth, I think I was just a little bit ashamed about the thing, because I had to pull it off. I didn't like the looks of it after I got it on."

Two small tanks, each with a capacity of approximately two gallons, were mounted over the engine in the positions they still occupy, the one on the left for gasoline, the other for water. The small fitting under the gasoline tank has a thumbscrew shutoff and a glass-sight feed tube, leading to the carburetor. The water tank, an inch longer than the gasoline tank, communicates with the water jacket of the engine through two pieces of half-inch pipe, entering the jacket from above and below. The overflow tank, holding just over a gallon, is suspended between the rear axle and the flywheel.

A number of mufflers were constructed for the engine. The first experimental one was built of wood, being a box 6 × 6 × 15 inches with a hole for the exhaust pipe in one end and a series of small holes in the opposite end. Inside, Frank arranged metal plates which were somewhat shorter than the depth of the box. Every other one was attached to the bottom of the box; the intermediate plates were fastened to the top. This contrivance muffled the sound considerably, but, as might be expected, soon began to smoke. There can be little doubt that it was replaced before any of the outdoor trials began. Another type consisted of a cylindrical metal shell, perhaps six inches in diameter and ten or twelve inches long. Here a series of perforated baffle plates were inserted, with alternating solid plates having parts of their external edges cut away. Two bolts running the length of the muffler held on the cast-iron heads in a manner quite similar to the Model-T Ford mufflers of later years. Though partially satisfactory, Frank, in a November 6, 1957, interview, complained that it made a metallic sound. Perhaps this was the muffler he used from September to November 1893.

Figure 21.—Illustration of the no. 2 Samson battery
used by the Duryeas in their vehicle. (Smithsonian photo 46858.)

On August 28 Frank wrote to Charles saying the carriage was almost ready for the road and that he hoped to take it out for a test on the coming Saturday, "off somewhere so no one will see us…." There is no evidence showing whether the amount of remaining work permitted the proposed trial on September 2. The body was finally replaced on the running gear, at which time it was found necessary to raise the seat cushion several inches by the insertion of a framework made of old crating boards. This allowed sufficient room between the seat and the frame to suspend the batteries and coil. Six no. 2 Samson batteries were contained in this space, three on each side, in rows parallel to the side of the vehicle. The Samson battery consisted of a glass jar containing a solution of ammonia salts and water, with a carbon rod in the center, housing a zinc rod. It is difficult to understand why they used Samson batteries rather than dry cells; perhaps they were concerned with the mounting cost of the machine and were making use of parts already on hand. A coil, possibly from an old gaslight igniter system, accompanied the Samson batteries under the seat. This original coil is now missing.

The iron dash frame, previously recovered and provided with a rain apron to be pulled up over the knees in the event a heavy rain blew in under the carriage top, was bolted back in place. Frank and Mr. Markham gave the carriage a quick painting; later Frank admitted, "the machine never had a good job of painting." Before the motor wagon actually got onto the road, a reporter on the Springfield Evening Union got some statistics on it and an item appeared on September 16, giving the first public notice of the machine.

Figure 22.—From the Springfield Evening Union, September 16, 1893.
Text of Article

Toward the latter part of the following week, Frank was ready to give the product of his labors its first road trial. On September 21 the completed carriage was rolled onto the elevator at Russell's shop. Seeing that the running gear was too long for the elevator, they raised the front of the machine, resting the entire weight of 750 pounds on the rear wheels. Once outside the building, they pushed it into an area between the Russell and Stacy buildings. After dark, "so no one will see," Will Bemis, Mr. Markham's son-in-law, brought a horse and they pulled the phaeton out to his barn on Spruce Street. There, on Spruce and Florence Streets the first tests were made. The next day Frank wrote his brother saying, "Have tried it (the carriage) finally and thoroughly and quit trying until some changes are made. Belt transmission very bad. Engine all right." He did admit the engine seemed to be well loaded most of the time. He also had an idea in mind to replace the poor transmission, explaining the plan to Charles: "The three gears on secondary shaft have friction clutches, the two bevel gears on same shaft are controlled by a clutch which frees one and clutches the other at will. This provides a reverse."

Figure 23.—Type of spark coil the Duryeas are believed to have used in their electrical circuit,
as shown in a catalog illustration. (Smithsonian photo 46858-A.)

The Springfield Evening Union of September 22 carried a notice of the trial. This report, too, commented on the faulty transmission and the plan already in Frank's mind for the new transmission.

… The friction belt allowed of the speed being steadily increased or diminished at the will of the driver and caused no sudden forward motion of the carriage, but while this arrangement has many advantages it uses up the power so that the two-horse power furnished by the motor [somewhat less than the rating Frank gave the engine] was reduced to less than three-fourths horse power on reaching the main shaft. This would not be sufficient to propel the carriage up steep grades but would be sufficient to run the carriage on level road.

The inventors will do away with this belt in favor of a clamp gear and will make the drum wheel smaller. By this means there will be very little power lost in transmission to the shaft and by a patented arrangement the carriage may be started gradually but the speed must be increased by shifting the clamp gear to a succession of gears on the driving wheel of the motor. The speed of the carriage will be fixed permanently according to the size of the gear that the smaller one is shifted to. The test of the machine with the gear arrangement will be made soon.

In October Frank decided on another vacation and went to Chicago to see the Columbian Exposition. Charles had come up from Peoria to see the fair and the two talked over the progress on their motor wagon, and discussed the transmission problem. They gave particular attention to everything relating to engines and motor carriages, and Frank recalls seeing a Daimler quadricycle that impressed him with its performance. Just what decisions the two might have made there are unknown, yet it is likely that they agreed to give the old transmission one more chance to prove itself.

Returning to Springfield, probably in the first week of November, Frank gave the friction drive its final test, this time substituting a leather belt for the rubber one first used. Mr. Markham, though intensely interested in the experiments, apparently was dubious concerning the safety of the carriage. It had no brakes, and fearing failure of the transmission on a downgrade, he was reluctant to ride in the machine. On November 9 he asked Will Bemis to try it for him. The following day the Springfield Morning Union gave a description of the run:

Residents in the vicinity of Florence street flocked to the windows yesterday afternoon astonished to see gliding by in the roadway a common top carriage with no shafts and no horse attached. The vehicle is operated by gasoline and is the invention of Erwin Markham and J. F. Duryea. It has been previously described in The Union and the trial yesterday was simply to ascertain the practical value of a leather friction surface which has been substituted for the rubber one previously used. The vehicle, which was operated by Mr. Bemis, started from the corner of Hancock avenue and Spruce street and went up the avenue, up Hancock street and started down Florence street, working finely, but when about half-way down the latter street it stopped short, refusing to move. Investigation showed that the bearing had been worn smooth by the friction and a little water sprinkled upon it put it in running condition again. The rest of the trip was made down Florence and down Spruce street, to the residence of the inventors. They hope to have the vehicle in good working condition soon.

Figure 24.—Running gear of Duryea vehicle,
showing the second engine and
other parts as used in January 1894.

The same evening, the late edition ran a brief paragraph stating that "the test was made to determine the value of a leather friction surface for propelling the wagon, that had been substituted in place of the rubber surface, used in the former test." Bemis, according to Frank Duryea's recollection, was not impressed with the performance of the machine, saying "the thing is absolutely useless," and for a time it appeared that further support from Markham would not be forthcoming. Frank, believing eventual success to be near, drew up plans showing his geared transmission, and with these managed to gain Markham's partial support. Money for material and use of the shop was to continue, but Frank was to complete the work on his own time.

Now receiving no salary, Frank worked hurriedly on the transmission throughout late November, December, and the first two weeks of January. First discarding the old friction drum and shaft, and the shipper-fork carriage, he bolted a rawhide bevel gear to the lower surface of the flywheel. This turns two bevel gears, in opposite directions, on a countershaft directly underneath, approximately in the position of the old jackshaft. The right bevel gear is secured to the main countershaft on which two clutches are mounted, one on each side of the crankshaft. On a sleeve turning freely around the countershaft is mounted the reverse bevel gear and clutch. Three free-running clutch drums, the right one carrying the high-speed gear, the two on the left carrying the combination low speed and reverse gear between them, complete the countershaft assembly. The clutch assemblies are of Frank Duryea's design, having internal arms, expanding outward to press leather-faced shoes against the inner surface of the drum, thus securing the drum and its gear to the shaft. Behind this machinery is the jackshaft with its small differential on the right, two laminated rawhide gears meshing with the iron gears of the countershaft, and the internal-gear sprockets hanging on the small pinions at either end. A sliding cam bar, mounted nearly in the position of the former shipper-fork carriage, is operated by the vertical movement of the tiller handle to engage any one of the three clutches. With the tiller depressed, the vehicle is in reverse. Elevating it slightly puts it into low gear, and raising it still higher runs the machine at its highest speed.

Figure 25.—Half of Jackshaft, showing rawhide gears, double shrouded pinion and half of the Columbia differential.

Figure 26.—Half of Jackshaft showing double-shrouded pinion and half of the Columbia differential.

Figure 27.—Cam bar in foreground, operated by tiller,
actuates the various clutches of the transmission. The overflow gasoline tank
with the hand pump can be seen in the rear.

Text of Patent Letter

Figure 28.—A drawing and the first page of the specifications of the first patent issued to C. E. Duryea.
It can be readily seen that this drawing was not made after the plan of the first vehicle.
Larger size rotated image.

As the work moved nearer completion Frank realized that the final tests would have to be conducted on roads made icy by falling snows. He had considerable doubt whether the narrow iron tires would have enough traction to move the phaeton. Soon he devised an expedient for this situation, communicating to Charles on December 22 that he was "having Jack Swaine [a local blacksmith] make a couple of clutch rims so we can get over this snow and ice…. Our detachable rims referred to will be of ⅛ iron 1¾ wide and drawn together at one point by two screws, one on either side of felloe. It will be studded with calks in two rows."

Figure 29.—Mr. and Mrs. Frank Duryea examining vehicle in
the Smithsonian Institution before restoration.

January 18, 1894, was a day of triumph for Frank Duryea. Writing Charles about his success the next day he said, "Took out carriage again last night and gave it another test about 9 o'clock." The only difficulty he mentioned was a slight irregularity in the engine, caused by the tiny leather pad in the exhaust-valve mechanism falling out. Speaking of this trip, Frank recalled in 1956:

When I got this car ready to run one night, I took it out and I had a young fellow with me; I thought I might need him to help push in case the car didn't work…. We ran from the area of the shop where it was built down on Taylor Street. We started out and ran up Worthington Street hill, on top of what you might call "the Bluff" in Springfield. Then we drove along over level roads from there to the home of Mr. Markham who lived with his son-in-law, Will Bemis, and there we refilled this tank with water. [At this point he was asked if it was pretty well emptied by then.] Yes, I said in my account of it that when we got up there the water was boiling furiously. Well, no doubt it was. We refilled it and then we turned it back and drove down along the Central Street hill and along Maple, crossed into State Street, dropped down to Dwight, went west along Dwight to the vicinity where we had a shed that we could put the car in for the night. During that trip we had run, I think, just about six miles, maybe a little bit more. That was the first trip with this vehicle. It was the first trip of anything more than a few hundred yards that the car had ever made.

Now Frank could give demonstration rides with the motor carriage, hoping to encourage more investors to back future work. Cautious Mr. Markham finally got his ride, though Frank had to assure him that the engine of the brakeless vehicle would hold them back on any hill they would descend. The carriage on which he had spent so many hours was to see little use after that. Its total mileage is probably less than a hundred miles. Little additional work is known to have been performed on the carriage after January 1894; there is, however, a letter Frank sent his brother on January 19 which tells of contemplated muffler improvements. Another message was dispatched to Charles on March 22, mentioning the good performance of the phaeton on Harrison Avenue hill. This was possibly the last run of the machine, for no further references have been discovered.

Frank spent the months of February and March in preparing drawings, some of which accompanied their first patent application, while others were to be used in the construction of an improved, 2-cylinder carriage. Work on the new machine started in April. The old phaeton, in the absence of used-car lots, was put into storage in the Bemis barn. Later, on the formation of the Duryea Motor Wagon Company in 1895, it was removed to the barn of D. A. Reed, treasurer of the company. There it remained until 1920, when it was obtained by Inglis M. Uppercu and presented to the U.S. National Museum.

Footnotes

Text of Letter (page 14)

24 Nov 1920

Dear Mr Mitman

On the train I had some time to puzzle over that car. Been working nights to make up time lost in the day so did not hav much.

I made a sketch for you but did not show the spring that holds the circuit breaker in contact with the spark point. That thin finger was part of it. A spring was wound spirally--not helically--around the projecting end of the breaker pivot and the end of the spring hookt over the thin finger. See sketch herwith.

Just how the central end of the spring wire was fastened to the square of the pivot I do not kno. We did in some cases bore a hole thru and simply stick the spring thru but this put most of the action right at the bend in the wire and it broke quickly. So in other cases we fitted a light grooved spool or pulley and wound the spring around this and so avoided a sharp bend. If this was used it has been lost with the spring. A couple generations of boys playing in that barn was too many.

The Haynes steering sketch also worries me. If that vertical post came up thru that slot in the floor the crank had to be long as the sketch shows in order to get over to the driver conveniently. Then if he tried to make a complete circle with it he could not reach far enuf forward to do it easily. And he had to make a turn or two be cause H shows bevel gears of about same size so the post had to make same number of turns the worm made. Sketch herewith to illustrate my thought.

Text of Article (page 20)

NO USE FOR HORSES.

Springfield Mechanics Devise a New Mode of Travel.

Ingenious Wagon Now Being Made in This City for Which the Makers Claim Great Things.

A new motor carriage, which, if the preliminary tests prove successful as is expected, will revolutionize the mode of travel on highways, and do away with the horse as a means of transportation, is being made in this city. It is quite probable that within a short time one may be able to see an ordinary carriage in almost every respect, running along the streets or climbing country hills without visible means of propulsion. The carriage is being built by J. F. Duryea, the designer and B. F. Markham, who have been at work on it for over a year. The vehicle was designed by C. E. Duryea, a bicycle manufacturer of Peoria, Ill., and he communicated his scheme to his brother, who is a practical machanic in this city.

The propelling power is furnished by a two-horse power gasoline motor situated near the rear axle and which, when started, runs continuously to the end of the trip, notwithstanding the number of times the carriage may be stopped. The speed of the motor is uniform, being about 500 revolutions a minute, and is so arranged that it gives a multiplied power for climbing hills and the lower the rate of speed the greater power is furnished by the motor. The slowest that the carriage can be driven is three miles an hour and the speed can be increased to fourteen or fifteen miles an hour. The power is transferred from the driving wheel of the motor, which runs horizontally with the main shaft by an endless friction belt running on a drum wheel. The belt is controlled by a lever within easy reach of the driver and is shifted along the drum wheel to increase or decrease the speed. The driving wheel is about twenty inches in diameter, having in its center a depression to which the belt is shifted to stop the carriage.

The carriage can be reversed by shifting the belt from the end of the drum, which gives the forward motion to the opposite side beyond the depression in the driving wheel. The power which has been transferred to the driving shaft from the motor is in turn transferred to the two rear wheels of the carriage by a combination gear and sprockets. An endless chain connects the sprockets on the carriage wheels to the sprocket wheels on the driving shaft. All of the motive power is located under the body of an ordinary phaeton, the hight of which is not increased by the machinery. The motor is started by a crank which is easily applied to a shaft in the rear of the carriage and the gasoline is ignited in the cylinder by electricity. An automatic device stops the flow of gasoline into the cylinder when the motor ceases running. The gasoline is carried in tanks, which hold about two gallons, and which will run the carriage for about eight hours. The wagon is guided by a bicycle bar, and the speed is also controlled by this bar.

The method employed in this is as follows: To start the carriage press the lever down; to reverse it throw the lever up and to guide the wagon turn the lever either to the right or left. The front axle instead of turning horizontally plays up and down, in order that the machinery may be on a level with the rear wheels, while the front wheels are set on the axle by a pivotal joint and are connected with the guiding lever by bars with ball bearings. The carriage complete weighs about 220 pounds, and the essential features are already covered by patents while others are pending.

It is estimated that the carriages can be sold for about $400, and a stock company will probably be formed to manufacture them.

Text of Patent Letter (page 24)

United States Patent Office.

CHARLES E. DURYEA, OF PEORIA, ILLINOIS.

ROAD-VEHICLE.

SPECIFICATION forming part of Letters Patent No. 540,648, dated June 11, 1895.

Application filed April 30, 1894. Serial No. 509,466. (No model.)

To all whom it may concern:

Be it known that I, Charles E. Duryea, a citizen of the United States, residing at Peoria, in the county of Peoria and State of Illinois, have invented new and useful Improvements in Road-Vehicles, of which the following is a specification.

The object of this invention is to produce a road vehicle which shall be self-propelled, not unduly heavy, simple and easy of control and comparatively inexpensive, together with such minor objects as will become hereinafter apparent.

The invention more particularly relates to the construction and arrangement of parts for constituting the driving gearing and to the means for controlling the action thereof; to an improved manner of mounting the front, or steering, wheels upon the front axle, and of mounting the said axle relative to the running gear frame, and to the means for effecting the steering; to the appliances for the support of the motor and driving mechanism in an advantageous and efficient manner, and, generally, to improved and simplified details of construction throughout the vehicle, all as will hereinafter be rendered more apparent, and the invention consists in constructions and combinations of parts, all substantially as will hereinafter fully appear and be set forth in the claims.

Reference is to be had to the accompanying drawings, in which—

Figure 1 is a sectional elevation from front to rear of the improved road-vehicle. Fig. 2 is a plan view of the running and driving gear, the vehicle-body being understood as removed. Fig. 3 is a front elevation of the vehicle. Fig. 4 is a perspective view of the support and suspension devices for the driving mechanism. Fig. 5 is a vertical sectional view, longitudinally, through the shiftable driving-gear, the controlling devices employed in conjunction with this mechanism being seen in side elevation. Figs. and show the above-mentioned controlling devices as in operative relations differing the one from the other and also from that of Fig. 5.

Similar letters of reference indicate corresponding parts in all of the views.

The parts will now be described in detail with reference to said drawings, and A represents the body which is spring supported on the frame, B, of the running gear. This frame, as shown, is rectangular, and has the body-supporting springs, B, similar to those found in common carriages. This frame has, affixed thereto, at its rear ends, sleeves, a, a, which loosely embrace the rear wheel axle, D, which is the driven axle of the vehicle. The axle, E, for the front wheels is centrally secured to the running gear frame, B, by the horizontal king-bolt, b, whereby such axle may have a swinging movement relative to the frame in a vertical plane, but it has no swinging movement horizontally, the wheels being swivel-mounted on the ends of this axle peculiarly, as will shortly hereinafter be set forth.

The body, as shown, is in the form of an inverted box, the motor, H, and driving gear being accommodated within the downwardly opening inclosure constituted thereby, and the body also has the upwardly open box-like forward extension, or pit, A, for the accommodation of the feet of the rider, the rider's seat being constituted by the top forward portion of the box body. Some other suitable design of body may, of course, be used in lieu of this one shown.

The front wheels, d, d, are hung to the front axle, E, so that the center of each wheel base is in a line coincident with the axis of the pivotal connection which is provided between the journals for the wheels and the axle, which arrangement practically destroys any tendency to deflection from the course that might otherwise arise from striking an obstacle, and so renders the steering easier. In order to effect this the axle is formed with yoked ends, the yoke members, f, f, being above and below the longitudinal line of the axle. The short journal, g, shown for each wheel, has at its inner end an upwardly and downwardly extended arm, h, which is return-bent to be loosely embraced by the axle yoke, f, f. The cone pointed screws, c, passed through the yoke members, f, and into sockets therefor in the arms, h, of the journals, g, constitute the means for the swivel connection between said parts. The lock-nuts, c, manifestly, are employed with utility in this connection.

It will be perceived that inasmuch as in the arrangement shown, the pivotal connections

Letters printed upside down have been corrected. The transcriptions retain all typographical and gramatical errors.

Contributions from
The Museum of History and Technology:
Paper 35

The Borghesi Astronomical Clock
In the Museum of History and Technology

Silvio A. Bedini

DEVELOPMENT OF ASTRONOMICAL CLOCKS 32

DESIGNER BORGHESI 33

CLOCKMAKER BERTOLLA 34

FIRST BORGHESI CLOCK 38

SECOND BORGHESI CLOCK 41

BORGHESIAN THEORY OF THE UNIVERSE 54

LAST YEARS 57

THE CLOCKS OF BARTOLOMEO ANTONIO BERTOLLA 59

APPENDIX 71

BIBLIOGRAPHY 76

INDEX

Figure 1.—The dial plate of the Borghesi clock, showing the horary and astronomical indications which are automatically presented.

Silvio A. Bedini

The Borghesi Astronomical Clock
In the Museum of History and Technology

The history of the 18th-century Borghesi astronomical clock is described here from contemporary source material. The evolution of its design by Father Francesco Borghesi and the building of the complex mechanism devised by the clockmaker, Bartolomeo Antonio Bertolla, is a story of the vision of one man turned into reality by another. The result of their collaboration is the unique, astronomical timepiece now in the Museum of History and Technology.

The Author: Silvio A. Bedini is curator of mechanical and civil engineering in the Smithsonian Institution's Museum of History and Technology.

“… All this work I had performed eagerly, so that, while in my room, I might contemplate leisurely, both during the day and in the night, the true face of the heavens and of the seas unobscured by clouds, even though I had no astronomical equipment.”

With these words, Father Francesco Borghesi (1723-1802) of Mechel described the reasons which inspired him to invent a unique astronomical clock which is now in the horological collection of the Museum of History and Technology.

This complicated mechanism, which performs a multitude of functions, was designed by Father Francesco Borghesi, a secular priest in Venezia Tridentina. It was constructed in 1764 under his direction by a provincial clockmaker named Bartolomeo Antonio Bertolla (1702-1789) of Mocenigo di Rumo. It was the second of two complicated astronomical clocks which Father Borghesi designed and which Bertolla constructed. According to contemporary sources, this clock was presented to the Empress Maria Theresa of Austria soon after its completion.

Its history is rather hazy, except for the fact that in 1780 this second Borghesi timepiece was still in the Imperial Palace in Vienna. The clock was again noted in 1927 when it was sold at a public auction in New York. Subsequently, it was acquired for the Smithsonian Institution.

ACKNOWLEDGMENTS

The author wishes to acknowledge the valuable assistance received from the following: Dr. Amos Avery, Amherst, Massachusetts; Mr. Edwin A. Battison, curator of light machinery and horology, U.S. National Museum; Dott. Richard Blaas, Oesterreiches Staatsarchiv, Vienna; Dott. Adolfo Cetto, librarian, Biblioteca Comunale di Trento, who made copies of Borghesi's two volumes available; Signor Mario di Mario, editor of La Clessidra, Rome, who permitted several of the illustrations in Sig. Luigi Pippa's article to be used herein; Mr. Walter A. Gilbert, Norwich, Connecticut; Dr. Heinrich Linardi, Uhrenmuseum der Stadt Wien, Vienna; Signor Luigi Pippa, Milan, Italy; Cav. Ing. Guido Ucelli di Nemi, Presidente, and Dott. Federico Morelli and Cav. Orazio Curti of the Museo Nazionale della Scienza e della Tecnica, Milan, for their cooperation on the descriptions and illustrations of the restored clockshop of Bartolomeo Antonio Bertolla; and Dr. Edward Waters, Division of Music, Library of Congress, Washington, D.C.

The translation from Francesco Borghesi's Latin texts, which made this study possible, were made by: Rev. Neil Herlihy, S.J., Rev. Francis J. Heyden, S.J., and Rev. Stephen X. Winters, S.J., Georgetown University, Washington, D.C.; and Rev. Daniel Hunter, O.P., and Rev. Robert Stenger, O.P., Dominican House of Studies, Washington, D.C.

Development of Astronomical Clocks

The history of the great theoretical and mechanical achievement which the Borghesi clock represents has been most adequately covered elsewhere. Consideration of the development of equation and astronomical clocks is required here only for the purpose of relating the Borghesi timepiece with the other significant developments in this branch of horology.

The invention of the anchor escapement in about 1670, and the consequent greater accuracy in time-telling, led to increased preoccupation with precision. Daily differences in time as recorded by sundials and clocks became more noticeable. Finally, in the second half of the 17th century, some attempt was made to construct mechanical clocks combined with sundials as well as astronomical clocks.

With the improvement of precision time-telling, it became necessary to reconcile the actual difference between true and mean time. Although a great variety of time-equation tables were produced, there was a considerable margin for error in their use. This led to the construction of mechanical clocks in which the equation of time was automatically accomplished. A few were produced late in the 17th and early 18th century at considerable cost and, consequently, with little popularity. Equation sundials were also developed which were elaborately ingenious, but they were not completely practical. Inevitably, they were supplanted by the mechanical equation clock.

Probably the first documented mention of an equation clock is in the diary of John Evelyn who recorded that in 1666 he visited the Royal Society where he witnessed a curious clock, which showed the equation of time, being presented by a certain Mercator. More data on the subject appeared in the first two decades of the 18th century, when Henry Sully, Joseph Williamson, Daniel Quare, and Thomas Tompion—who were among the foremost English clockmakers of all time—produced elaborate examples of these timepieces. Another significant maker was Dowe Williamson, who became Court Clockmaker to Emperor Charles VI of Austria. In London, Joseph Williamson produced some of the finest astronomical timepieces of this type that have been known. The interest in the subject next shifted to France where many fine examples were produced during the first half of the 18th century.

Just after the middle of the 18th century, the subject of astronomical clocks suddenly became a major horological preoccupation in another region, namely, Austria, where the work in this field was apparently done exclusively by members of the clergy. The earliest was Father Philipp Matthäus Hahn (1739-1790) of Württemberg. Father Hahn considered the equation of time as only one part of a plan to represent astronomical occurrences by means of clockwork. In addition to planetaria and similar mechanisms, Father Hahn produced two extraordinary astronomical, tall-case clocks, both of which survive in public museums.

Figure 2.—Portrait of Father Francesco Borghesi, inventor and designer of the astronomical clock in the Museum of History and Technology.

Another of the clerical clockmakers was Father Aurelianus à San Daniele (1728-1782), an Augustine monk in the monastery of the Imperial Court at Vienna. His four complicated astronomical clocks, which exist in museums at present, are comparable to those produced by Father Hahn. The third cleric was Brother David à San Cajetano (1736-1796) in the same Augustine order to which Father Aurelianus belonged. He achieved note as the author of various publications, including Neue Rädergebäude [New Construction of Wheels] relating to planet-wheels, or gear-trains containing epicyclic elements. He constructed a clock based on an elaborate astronomical design which was substantially different from the others. The fourth of the ecclesiasts who designed astronomical clocks in this period was Father Klein of Prague, who produced a complicated astronomical timepiece in about 1738.

The fact that such important and outstanding examples of astronomical clocks were produced exclusively by ecclesiasts in Austria during the second half of the 18th century is especially significant. It is particularly so when a fifth cleric is added to the group, also an Austrian subject although Italian by heritage, in the person of Father Francesco Borghesi.

Although only Father Borghesi's second astronomical clock is now known, it is apparent that this example in the Museum of History and Technology represents an experiment in astronomical time-telling comparable to any of the timepieces produced by Father Hahn, Father Aurelianus, Brother David à San Cajetano or Father Klein.

This combination of five clerical clockmakers who lived in the same region during the same period of time is sufficiently unusual. However, the fact that each of them apparently worked without association with any of the others leads to the conjecture that a common factor must have led them to their individual preoccupation with astronomical horology. What the link may have been is not apparent from the surviving records of the lives and works of these clerics. Certainly it was not an interest in astronomy or clockmaking per se, because other than the astronomical clocks, none of these horological inventors—with the possible exception of Father Hahn—worked in any other aspect of the fields of astronomy or horology. However, after a comprehensive study of Father Borghesi's writings, there is little doubt of the religious basis of his own inspiration.

Designer Borghesi

Father Borghesi's story takes place in the picturesque mountainous region of what was then known as Venezia Tridentina (since 1947, Trentino-Alto Adige) in northern Italy, along the Tyrolean border of Austria. Because of its strategic position as the passage between Innsbruck and Verona, the possession of the Tridentina was contested again and again in the European wars, but during Father Borghesi's lifetime, the Tridentina was under Austrian domination.

Figure 3.—Panorama of the village of Mechel in the valley of the Non, birthplace of Father Borghesi.

Deep within this mountainous district is the romantic valley of the Non, or Anáuni, with its great forests and ancient castles. Most maps do not mark it, and the tourist guides ignore it. One of the chief communities is Cles, with its historic Renaissance buildings. The major city of the region is Trent on the Adige River, with its surviving Roman relics and Romanesque and Renaissance architecture.

The little villages scattered throughout the valley of the Non played no part in history, but such names as Mechel and Mocenigo di Rumo reflect the interchange of sovereignty. It was in the little village of Mechel that Francesco Borghesi was born in 1723. Local records are meager and inadequate, and many of the details of Borghesi's life must be assumed. Inasmuch as the village was in a rural, agricultural district, Borghesi may have come from a family of farmers, vintners, or village tradesmen. Borghesi sought an education by entering the priesthood and was ordained a secular priest in Salzburg. He was first assigned as curate to the village parish of Rumo in the valley of the Non, a short distance from his birthplace. Later, he was transferred to his native Mechel. He was inherently a man of simple tastes and of great piety. He tended to the needs of his mountain villagers and attended the births, weddings and deaths of his parishioners. It was during his assignment in this tiny community that Father Borghesi met and became friendly with the clockmaker, Bartolomeo Antonio Bertolla of nearby Mocenigo di Rumo.

Clockmaker Bertolla

Bartolomeo Antonio Bertolla was born in Mocenigo di Rumo, a short distance from Mechel, in 1702. Nothing is known of his boyhood, other than the fact that he was mechanically inclined. At the age of 17 he was apprenticed to become a clockmaker with the master, Johann Georg Butzjäger of Neulengbach, a small village on the edge of the great Vienna woods. This region was then part of the domain of the Archduke of Austria, of which Sankt Pölten was the capital.

Figure 4.—Portrait of Bartolomeo Antonio Bertolla, clockmaker, of Mocenigo di Rumo. The canvas in oils is owned by descendants. In the upper left-hand corner is an inscription, now hardly legible, indicating that the portrait may have been painted after Bertolla's death on January 15, 1789. Translated, it states: "Bartolomeo Antonio Bertola [sic] Celebrated Mechanician and Inventor of various Instruments. Repairer of the clocks of Venice, Verona, Trent, and other localities. Maker of the Work which combines the Copernican and Ptolemaic Systems devised by Father Francesco Borghesi of Mechel, Laureate Mathematician, and humbly offered to Her Imperial Majesty Maria Theresa. Died in piety in his home at Rumo on 15 January 1789 at the age of 86." (Courtesy of Sig. Luigi Pippa of Milan.)

Figure 5.—The village of Mocenigo di Rumo in the valley of the Non. Arrow points to Bertolla's home and workshop at far left.

Figure 6.—Certificate of apprenticeship awarded to Bartolomeo Antonio Bertolla upon completion of his 3-year apprenticeship at Neulengbach, dated December 27, 1722.

Bertolla began his apprenticeship with Butzjäger under the auspices of the Corporation of Blacksmiths of Sankt Pölten in 1719. His training was supervised by two master locksmiths, Johann Christian Winz and Peter Wisshofer, who were members of the Corporation, and were assigned to serve as patrons for the apprentice. It was their obligation to make certain that he received good care and adequate instruction from his master. While he worked in Butzjäger's shop, Bertolla lived with the master's family in their home.

Bertolla's 3 years at Neulengbach passed quickly as he sought to absorb all that his master could teach him. Butzjäger was considered to be a good craftsman in the region, yet today there is not even a mention of his name in the lists of clockmakers. He specialized in the production and repair of "great clocks" which included tall-case, domestic timepieces, and tower clocks. Butzjäger treated his apprentice well, and in return Bertolla rewarded him by being diligent and honest. His subsequent work is sufficient indication that he developed into an extremely skilled craftsman, and he became the equal of any clockmaker of his time.

The 3 years of apprenticeship were completed and on December 27, 1722, Bertolla received a certificate from the Corporation of Blacksmiths which assured whomever it might concern of Bertolla's skill, diligence and honesty, and permitted him to open his own shop as a clockmaker under the auspices of the Corporation. This document, which has been preserved by Bertolla's descendants, is an interesting record of the organization of the trade guilds in the 18th century, and, for that reason, has been translated from the original German:

We, the Superiors and other masters of the honorable corporation of municipal blacksmiths, armorers, and of smiths, in the Imperial City of St. Pölten in Austria by the river Enns, Declare by these Presents put in force by this document to anyone who waits to hear…. That the honorable and able Bartolomeo Antonio Bertolla of Rumo in Lentzberg, the Tyrol, on the 27th day of the month of December of the year 1719 was consigned as apprentice for three years, in the presence of two sponsoring masters for the purpose, the honorable Johann Christian Winz and Peter Wisshofer, both of them master locksmiths representing the entire honorable Corporation and others of open shop—to the honorable Johann Georg Butzjäger, incorporated with us, citizen and master clockmaker for large clocks in the merchant-village of Neulengbach in Wienerwald, as his master of the art, would have therefore perfectly and rightfully worked and learned, and

that afterwards, on the day and year noted at the bottom, he will be newly declared free and independent before us, representative of an entire and honorable Corporation and with open shop, of his above-mentioned master and of the two sponsoring masters mentioned,

and since he eagerly requested a truthful certificate of apprenticeship for his honest service as an apprentice and for his good behavior, and we having great pleasure as well as the duty of favoring the truth and well knowing that the aforesaid Bartolomeo Antonio Bertolla has learned honestly the art of clockmaking for great clocks from his aforesaid master, and that he has always behaved with honesty, obedience, faithfulness and diligence both towards his master and towards us to our complete satisfaction and, therefore, we cannot in any manner refuse his request, rather we wish to grant it with a clear conscience.

We Therefore Address to Everyone and to anyone in whatever state and rank, but particularly to those interested in our branch of this art, our respectful and courteous entreaty and request to consider Bartolomeo Antonio Bertolla well recommended for his honest apprenticeship and his good behavior, and to desire to favor him in every way, in such a manner that will assure our gratitude whenever an occasion presents itself.

For this purpose, we issue, as we have declared we wish to issue to you, Bartolomeo Antonio Bertolla, this certificate of apprenticeship, attaching to it the seal of our Corporation.

Executed in the city of St. Pölten on 27 December 1722.

His apprenticeship over, Bertolla returned to his native region where he soon established a reputation for himself as one of the most skillful clockmakers in the Tridentina and produced timepieces of fine quality in some quantity. No records have survived concerning his personal life, but it is believed that he married probably soon after his return. He had no children of his own. To expand his business, he eventually took into his shop two nephews, the sons of a brother and a sister, as apprentices.

Bertolla's work brought him a sufficient number of clients, and he produced elaborate clocks for his more wealthy patrons.

In 1752, it is recorded that he repaired the great clock in the campanile of the Church of the Assumption of the Virgin Mary in Cles, the regional capital of the valley of the Non. The clock dated probably from the 16th century, and it seems likely that Bertolla replaced the original two-wheel train with a three-wheel movement, and that he added the present anchor escapement.

It is not possible to determine when Father Borghesi first made Bertolla's acquaintance, but it may be assumed that they had become friends in the late 1750's.

After he had come to know Bertolla, Father Borghesi apparently spent many hours in the clockmaker's shop. He was fascinated by mechanics in any form, and the complications of clockwork particularly intrigued him. Bertolla was patient with the young priest, explaining the tools he had and their uses, the clocks he produced or repaired, and the principles which were involved. Father Borghesi listened willingly and as his understanding of timepieces grew, his curiosity increased.

In spite of himself, the priest could not be satisfied with the ordinary aspects of his friend's work and wanted to learn more. From a casual pastime, the study of time became an obsession with him. There was but one recourse: he went back to studying once again. This time it was not theology, however, but the sciences. Every moment he could spare went into the perusal of books on mathematics, astronomy, and associated subjects. He progressed rapidly, driven by his overpowering interest and aided by his quick intellect.

Little by little, Borghesi managed to acquire the basic texts that explained this new world to him, probably borrowing them from old seminary friends. As each new book came into his hands, he devoured it in his desire to master its contents. He discussed each new principle or precept that he learned with Bertolla. Together, they attempted to apply his new learning to the calculations necessary for a timepiece which would demonstrate the astronomical theories in visual form. Borghesi taught himself slowly, step by step, and the result was a profound understanding of astronomical science. He conceived the project of constructing a great astronomical clock which he felt could be accomplished by combining Bertolla's mechanical skills with his own recent mastery of astronomy and mathematics.

First Borghesi Clock

It is not difficult to visualize the two men, the priest and the clockmaker, as they sat together night after night working out their plans. Father Borghesi would painstakingly outline the astronomical principles he wished to have the clock exhibit and the mathematical principles which would be involved to operate them. Bertolla concentrated on them and tried to transcribe the principles into functional mechanical terms, visualizing each operation in terms of wheels and gears. Little by little the two men coordinated the numerous elements and welded them into an operating entity. They adjourned either to the stark simplicity of the rectory or, probably more often, to Bertolla's little home workshop, the priest standing over his friend while the latter worked at his bench in the dark paneled interior illuminated only by the several lamps on the work benches.

This first clock which the two men combined to create is a monument to the great scientific knowledge of the self-taught priest and the technical ability of the clockmaker—a unity combining astronomical science, mechanics, and artistry. The story of the project is told in a little book, Novissima Ac Perpetua Astronomica…, which Borghesi later published. Explaining the incentive which inspired him, and the premises from which he began his work, he wrote:

From the foundation of astronomical science long ago, innumerable [and] repeated observations of both ancient and modern astronomers, emerged at last from their hiding places. Made light of by the jests of so many outstanding intellects, they have so successfully brought to light the paths of the stars and their motions, which are more complicated to us than the Gordian knots. Now it is possible for even an amateur in astronomy, sufficiently instructed, to predict for any given time not only the mean position of the planets, but also their true longitude and latitude, and even the true time of their conjunctions, and their ecliptic oppositions, with all the attendant circumstances. Yet, until now, no hypothesis has been devised which would force an automaton to show to us, before our very eyes, the eclipses of the planets in their true and certain times.

For though there have been men seeking with all their might to bind by laws their artificial heavens, by I know not how many and how great calculations, and to systematize the complexities of the rotations of celestial bodies; nevertheless, all of them, as if by common agreement, considered themselves to have made great contributions to mechanico-theoretical astronomy. However, they have only attained, even though closely, the mean locations of the secondary mobiles, and those by a certain rather crude calculation. Some attained by more, some by less, but all by some degree of wandering from the truth, either worn out by the intricacies of the motions, or deceived and deceiving by the errors of their calculations. This fact those well know, who, setting about to collect information of this kind, even those publicized not long ago, with true astronomical calculation, have been bored to death while digging out by the most elementary and superficial arithmetical torture, the worst of fallacies spontaneously erupting from thence.

It would seem that true calculations alone can be desired in mechanico-astronomics. Long study had not only convinced me that an automaton was within the realm of possibility, but that there were many mechanical systems by which it could be achieved. I girded myself for a new project and developed it theoretically from the ground up, but under such unhappy auspices that not only did all hope fail that anyone would ever appear who might have seemed willing to set his hand to the work, but that the new discovery itself was scoffed at by many as altogether a nightmarish delirium of an unbridled imagination.

The first months of the project must have seemed like an inspired dream to the two men, and then must have followed a period of hopeless depression. Bertolla undoubtedly felt many times that the clock was an aspiration far beyond their combined abilities and means, but the priest would not be thwarted in his ambition and refused to abandon the project. He felt that it was a work that they were destined to produce. Many times, he wrote, he chided and begged and shamed his erstwhile partner into resuming the project where it had been last abandoned. Little by little, the first clock began to take form. As each new difficulty was encountered, the two men would go back over the notes and sketches to trace the problem to its source. Often a new part of the mechanism would nullify another which had thus far operated successfully, and a complete rearrangement would be required.

Figure 7.—Title Page of Father Borghesi's first book. The translation in its entirety is: "The Most Recent, Perpetual, Astronomical Calendar Clock: Theoretical—Practical: by means of which besides the hours, the minutes and seconds; the current year, the month; the day of the month and the day of the week; the dominical letter, epact, and thence, the day of all the feastdays, both fixed and movable; the solar cycle; the golden number; the Roman indiction; the dominant planet of any year and its sign; the phases of the moon and its mean age: and all the motions of the sun and the moon as to longitude, latitude, eccentricity, etc., are immediately seen, so accurately that [not only] the true new full moons and the true quadrature, etc., of the sun and moon appear, but also, all solar and lunar eclipses—both visible and invisible; as in heaven, so on the clock, they are conspicuously celebrated in their true times, and those of the past and those of the future, with their circumstances of time and duration, magnitude, etc., can be quickly determined. All this was devised and brought to light by the author, Francesco Borghesi of Anáuni, a secular priest of Trent, A.A.L.L. & Doctor of Philosophy. (Trent: From the printshop of Giovanni Battista Monauni, With Permission of Superiors.)" (Title page reproduced by permission of the Biblioteca della Citta di Trento.)

Again and again, Bertolla threw up his hands in despair and begged Father Borghesi to abandon the enterprise. He protested that he was not capable of producing such a complicated mechanism; he had neither the tools nor the skill. The priest wished to produce a clock such as the world had never seen before, such as the greatest scientists and clockmakers of all time had never been able to make. But Bertolla felt that he was only a provincial craftsman who could not hope to surpass them all with only his simple tools and training.

In his book on the first clock, Novissima Ac Perpetua Astronomica…, Father Borghesi wrote that when he had finally come within a few weeks of the embryo stage in the development of his clock, he was faced with the problem of bolstering the sagging enthusiasm of Bertolla. The clockmaker's original enthusiasm had shown promise of great results, but as the days passed and the problems of the multiplex and generally unfamiliar apparatus to be forged for the workings of the automaton became more complex, his ardor decreased. Finally, Bertolla became so discouraged by the scoffers and frustrated by the fact that the work was insufficiently organized that Father Borghesi wrote that "it almost became a harder task for me to bolster up by daily opportunity and importunity the failing patience of the artisan, frightened away from the work already begun, than it was for me to extract from the inner recesses of mathematics and astronomy, without light and without a guide, the whole fabric of the machine itself!"

In spite of Bertolla's protests, Father Borghesi prevailed, reviving his friend's interest once more until the two were deep in the project again. Months passed as they worked together on the mechanism and it seemed as if they lived for no other purpose. Inevitably, Bertolla's health began to suffer, undermined as it was by the constant nervous tension, and he eventually became ill from mental strain. He was forced to spend some time in bed, and for many weeks the subject of the clock was not discussed. Bertolla's other work, by which he made his living, suffered and it was several months before he was able to return to his little shop.

One year passed into another and the work progressed slowly. The first clock, which easily should have been finished in less than a year, was not completed until after three full years had passed. However, when the priest and the clockmaker put the finishing touches to their great clock, the result surpassed the greatest possible expectations, for it was truly a masterpiece. Not only did it illustrate the ecliptic phenomena of the moon, the sun and earth occurring in their proper time, as well as many other things, but it showed these operations as they succeeded in proper order, taking place through the centuries.

With mutual feelings of great pride, the two friends surveyed the result of their three years of endeavor. Bertolla realized that he had reached a point of maximum achievement in his work. He probably felt that now he could relax again, that his sleep would no longer be troubled by confused nightmares of wheels and gears that did not mesh together. Time was to prove otherwise.

PUBLISHED DESCRIPTION OF THE FIRST CLOCK

Father Borghesi soon came to the conclusion that it would be desirable to have a written description to explain the mechanism of the clock and its many indicators. He thereupon wrote out the story of how the clock was made, the reasons for embarking on the enterprise, the difficulties he had encountered, and the success which had crowned his and Bertolla's mutual labors. Finally, he described the operation of the clock's mechanism and the functions of its array of indicators.

The little book was written in Latin and only a few copies were printed, presumably at the priest's own expense, on a handpress by Giovanni Battista Monauni, printer to the Bishop in Trent. The little volume was stated by contemporary writers to have been published in 1763, although no date appears on the title page. The title translated is, in part, The Most Recent, Perpetual Astronomical Calendar Clock, Theoretical—Practical…. The work begins with an introduction for the reader in which Father Borghesi stated that:

… the little work, which, as far as I was concerned could easily have been finished in a year, was only completed after about three years. Fortunately, however, it was so far beyond the expectations of most, that not only am I able to foretell with certainty all the lunar ecliptic phenomena and the solar, or rather terrestrial, phenomena, carefully worked out in their true periods, among many other matters exhibited by the machine; but also, within a few hours, I can exhibit by altogether tangible evidence to the skeptics and the doubting those very same phenomena, occurring within the space of many years, or even centuries, and succeeding one another in proper order, with their many attendant circumstances. I was not much concerned about the other eclipses, such as those of Mercury, Venus, and the other stars wandering through the zodiac, or about the other solar eclipses from the transit of Mercury or Venus, since they are altogether undiscernible to the naked eye, and very few compilers of ephemerides wish them to be noted, probably for the same reason.

Do not, however, expect, star-loving reader, that here anything at all that you may wish can be drawn forth as from its source, for to demand this would be almost the same as to seek to drain as from a cup all the vast knowledge of the many arithmetical sciences from the narrow confines of one book. You will understand how impossible that is when, through prolonged labor, you have grown somewhat more mature in this kind of learning.

Wherefore, rather fully, and out of consideration for you, I have decided, setting aside these prolixities, with completely synoptic brevity and with all possible clarity to expound for you simply the proportion of the movements, the description of the machine, and its usage. As a result, when you have progressed a little in theoretical mechanics, you will not only be able to reduce all these things to their astronomical principles, but you may find the way more smoothly laid out for you even for perfecting the machine itself. And, thus, you may be more effectively encouraged to a successful conclusion. Let it be so now for you through the following 10 chapters!

After these rather hopeful assurances, Father Borghesi proceeded to provide a detailed description of the clock dial and functions in the 10 short chapters which he had promised, under a separate section entitled "Synopsis Totius Operis Mechanici," which is translated in its entirety in the appendix.

As Father Borghesi prepared his little volume about his first clock, and described its unusual features and outlined its functions, which were primarily to place in evidence the celestial constellations, it occurred to him that it would now be easier after the experience he had acquired with his first timepiece, to construct another clock, which would present the motions of the two astronomical systems, the Ptolemaic and the Copernican. In this first book, he promised the reader that he would undertake the second project. It is fortunate that Father Borghesi undertook this project for the second clock is the only example of his work that is known to exist today. Extensive research has not shown what happened to the first clock, although several sources state that both timepieces were presented to Empress Maria Theresa sometime between 1764 and 1780.

Second Borghesi Clock

Figure 8.—The Borghesi clock in the Museum of History and Technology, constructed in 1764 by Bartolomeo Antonio Bertolla of Mocenigo di Rumo from the designs of Father Francesco Borghesi of Rumo and Mechel.

Father Borghesi lost no time in initiating the project of the second clock. The first and most important step was to inform Bertolla and enlist his assistance. Bertolla was adamant: he had had enough of complicated astronomical movements. He was delighted by the prospect of returning to his former simple life, producing simple, domestic, elementary movements for his country clients. Father Borghesi begged and cajoled. The second clock would be a much simpler one to construct, he persisted. After all, they had gained invaluable experience from the production of the first clock. Furthermore, he had already completed its design.

Bertolla apparently wavered in his resolve and, unwillingly and against his better judgment, he allowed the priest's inducements to prevail. Once again, the two friends yielded their leisure hours to a study of the priest's books and drawings as Father Borghesi enthusiastically elaborated his design for the timepiece, and Bertolla attempted to transcribe astronomical indications into terms of wheel counts. The second clock was, as Borghesi had promised, much easier of execution. Within a year, it was completed and functioned with complete success.

Figure 9.—Another view of the Borghesi clock.

This is the clock now in the Museum of History and Technology. It is housed in a tall case of dark-red mahogany veneered on oak, with restrained carving featuring ribands and foliate motifs. Gilt-brass decorations flank the face of the hood, which is surmounted by three gilt-brass finials in the form of orbs. A wide door in the waist may be opened to attend the weights. The case is 7 feet 8 inches high, 20/2 inches wide at the waist, and 14 inches in depth.

The dial is of gilt brass, measuring 21 inches high and 15 inches in width, with a number of supplementary silvered dials visible through its openings. Instead of hands, the dial utilizes three concentric rings moving around a central disc, the indications of which are read at two bisecting gilt lines inscribed in the glass face. Twelve separate functions are performed by the chapter ring assembly alone, and there are 14 openings on the dial. It is estimated that the clock performs 30 separate functions, including striking and chiming. Of the multiple chapter rings, the outermost is 1/8 inches wide, the center ring is /8 inch wide, and the innermost ring measures 1/4 inches in width.

THE DIAL-PLATE ENGRAVINGS

The gilt dial is incised throughout with figures and inscriptions in engraving of the very finest quality, as is evidenced in the illustrations. The frontispiece is surmounted at its center by the crowned double eagle of the House of Hapsburg, indicating the identity of the sovereign in whose reign it was made, Emperor Francis I or the Empress Maria Theresa of Austria. Below the eagle at either side are flying cherubs supporting ribands with inscriptions. Centered at the bottom of the frontispiece immediately above the chapter rings is the moving silvered orb representing the sun. Surrounding it is a tableau of the Holy Trinity, with the Virgin Mary being crowned by Christ holding a cross at the left and God with a sword in hand at the right, and a dove representing the Holy Spirit hovering over the Virgin's head. Father S. X. Winters, S.J., considers it reminiscent of the triptych "The Coronation of the Virgin" by Fra Lippo Lippi.

Figure 10.—Diagram of the dial plate.

Figure 11.—Dial plate of the Borghesi clock.

KEY TO DIAGRAM OF THE DIAL PLATE

A Dominating planet, represented by its symbol and its house;

B Dominical letter (Lit. Dom.);

C Epacts (Cyc. EpEC);

D Roman indiction (Ind. Rom.), part of the reckoning of the Julian period;

E Solar cycle, (Cyc. Sol.), part of the reckoning for the Julian period;

F Golden number (Num. Aur.), part of the reckoning for the Julian period;

G, H, I, J The era, or the current year; part of the six windows of the Iris, or rainbow;

K Shuttered winding hole, for winding up the weights; part of the six windows of the Iris;

L The era, or the month of the current year; part of the Iris, or six windows of the rainbow;

M The sun in its epicycle;

N The 12 signs of the sun's anomaly;

O, P The first chapter ring representing the equatorial globe of the week, revolving from left to right;

Q The coming day indicated through the window;

R The second chapter ring; including the synodic-periodic measure of the tides, the days of the median lunar-synodic age, the signs and degrees of the signs for mean distance of the moon from the sun;

S Epicycle of the moon with signs of its anomaly;

T Head of the dragon (Cap. Draconis);

U Tail of the dragon (Cauda Draconis), for measuring eclipses of the earth and of the moon;

V Third chapter ring, with degrees of lunar latitude and some fixed stars;

W Fourth chapter ring, showing firmament of fixed stars, signs of the zodiac and degrees of the signs, the months of the year, and days of the months, revolving left to right for the course of a mean astronomical year;

X Adjustment marked Claudit (it closes) and Aperit (it opens) for disengaging dial work for the purpose of making astronomical experiments and computations;

Y Adjustment marked Concitat (it accelerates) and Retardit (it retards) for fast and slow adjustments of the movement.

In the upper spandrels of the dial are two more cherubs bearing ribands with inscriptions. In the lower left corner is a magnificent engraving of Atlas upholding the globe of the world, inscribed with the zodiac, over his head. The lower right corner features the figures of two noblemen apparently examining and discussing an orb upon a table, the significance of which is not clear.

Figure 12.—Empress Maria Theresa, to whom Father Borghesi is stated to have presented his two astronomical clocks. The coin bearing her portrait is in the Museum of History and Technology.

Figure 13.—Portrait of Francis I, Emperor of the Holy Roman Empire, to whom Father Borghesi's astronomical clock in the Museum of History and Technology appears to have been inscribed.

THE INSCRIPTIONS

Beginning with the uppermost part of the frontispiece, there are nine inscriptions in Latin on the dial plate. The topmost is Franciscvs I sit plan. Dominator aeternvs. The phrase has reference to Francis I, who was Emperor of the Holy Roman Empire, from 1745-1765, and husband of Empress Maria Theresa of Austria. The phrase may be translated as "May Francis I be the eternal ruler by favor of the planets" or more simply "Long Live Francis I, Emperor." Although the dial plate of the Borghesi clock is inscribed with his name, the records indicate that the clock was presented to Maria Theresa. Francis I may have already died before the presentation was made.

From the left to right over the tableau of the Holy Trinity is the phrase "Lavs sacrosanctae Triadi Vni Deo, et Deiparae" (Praise [be] to the most Holy Trinity, to the one God, and to the Mother of God).

Within the upper left and right spandrels is inscribed:

Isthaec, Signum grande apparvit in Coelo * sancta Dei genitrix amicta sole * Illibato pede Lvnae et serpentis nigra premens Cornva * bis senis pvlcherrime Coronata syderibvs * Tempe indesinenter clavsa, scatvrigo signata * Cedrvs in Libano, Cypresvs in Monte Sion * Mater pvrae Dilectionis sanctaeqve spei * Chara patris aeterni proles, Verbi Mater, sponsaqve procedentis *, gratiae et gloriae circvmdata varietate.

This inscription is a eulogy to the Virgin Mary assembled from the texts of Holy Scripture. In addition, each lemma, contained within asterisks, carries out the chronogram 1764, the year the clock was completed. Each lemma is translated and identified from the Douay-Rheims version of the Bible:

This woman: a great sign appeared in Heaven (Apocalypse 12:1) * The Holy Mother of God clothed with the sun (Apocalypse 12:1) * And with unharmed foot crushing the black horns of the moon (Apocalypse 12:1) and the serpent (Genesis 3:15) * Most beautifully crowned with twice-six (Apocalypse 12:1) * A garden [Tempe ] enclosed, sealed with a fountain [spring of water] (Song of Songs 4:12) * Like a cedar in Lebanon, and a cypress tree on Mount Zion; (Ecclesiasticus 24:17) * Mother of pure love and of holy hope: Beloved daughter of the Eternal Father, Mother of the Word, Spouse of the Holy Spirit: (Ecclesiasticus 24:24) * Surrounded with a diversity of grace and glory (Psalms 44:10).

Figure 14.—The bottom right corner of the dial plate, showing two noblemen contemplating an orb, with the inscription "Diligit Avdaces Trepidos Fortvna Repellet." (Fortune favors the daring and rejects the timid.)

Figure 15.—The bottom left corner of the dial plate, showing the engraving of Atlas, with the inscription "Assidvo proni donant di cvncta labori." (The favorable gods willingly grant all things to the assiduous laborer.)

At the lower left corner below the figure of Atlas upholding the world is the phrase, Assidvo proni donant di cvncta labori. (The favorable gods willingly grant all things to the assiduous laborer.) The same phrase is quoted by Father Borghesi in the text of his second volume. The last inscription appears at the lower right corner under the figures of the two noblemen, Diligit avdaces trepidos fortvna repellet. (Fortune favors the daring and rejects the timid.) The last two inscriptions are in dactylic hexameter. They appear to be original compositions inasmuch as no classical prototypes have been identified.

Figure 16.—Detail of frontispiece of the Borghesi clock, showing the apertures for calendar indicators and the details of the engraving.

CENTER DIAL INSCRIPTIONS

In addition to the inscriptions previously noted on the outer dial plate, there are three major inscriptions in the central dial. The outermost states Circulus horarius Soli, Lunae, Fixis, Nodis, Aestuique marino communis (the hour circle, common to the sun, the moon, the fixed stars, the nodes and to the sea tide). This inscription is divided into four parts by the insertion of four divisions for the day into canonical hours: [Horae] Nocturnae (night hours); Matutinae (morning hours); Diurnae (daytime hours) and Vespertinae (evening hours).

The next section of the central dial is inscribed Intumescite—Detumescite (rise and fall of the tides) repeated at intervals of approximately every six hours. Within the next section is the following inscription, inscribed continuously around the ring:

Lege fluunt, refluunt, dormitant hac maris undae: Ad Phoebi et Phoebes concordia iussa moventur Aequora; discordi iussu suspensa quiescunt.

Translated, this is:

By this law the sea waves ebb and flow and lie dormant: When Phoebus and Diana agree in their commands, the waters are moved; when they disagree, the waters lie silent.

Within the central boss of the dial plate, the name of the maker is inscribed:

Bvrghesio Doctore, et Bertolla Limatore Annaniensibvs*

Translated, this is:

[By] Doctor Borghesi and Bertolla, mechanician citizens of Anáuni.

INDICATORS IN THE FRONTISPIECE

There are 12 windows in the frontispiece, through each of which appears an indication relating to time. Beginning at the top of the frontispiece of the dial, the first opening occurs on the breast of the imperial eagle. This indicates the dominating planet, represented by its symbol, and its house.

The opening in the eagle's left claw, labeled "Lit. Dom." is the dominical letter. The first seven days in the month of January are each assigned one of the letters a through g in order of appearance. The letter which coincides with the first Sunday within this period is called the dominical letter, and it serves for the following year. In leap year, two letters are required, one to February 29th and the letter next proceeding for the remainder of the year. This letter is used in connection with establishing the date of Easter Sunday. The date of Easter regulates the dates of the other movable feasts.

The eagle's right claw is labeled "Cyc. EpEC" and represents the epact, or the age of the moon on January 1st. It serves to find the moon's age by indicating the number of days to be added to each lunar year in order to complete a solar year. Twelve lunar months are nearly 11 days short of the solar year, so that the new moons in one year fall 11 days earlier than they did the preceding year. However, 30 days are deducted as an intercalary month since the moon has made a revolution in that time, and the remainder, 3, would be the epact.

Below the imperial eagle two winged cherubs support a riband with three indictions of the Julian period. This period of 7980 years is the product derived from multiplying together the sums of 28, which represents the cycle of the sun; 19, representing the cycle of the moon; and 15, which represents the Roman indiction. The Julian period is reckoned to have begun from 4713 B.C. so that the period will be completed in A.D. 3267. The first of the three openings is marked "Ind. Rom." or "Roman indiction," which was an edict by the Emperor Constantine in A.D. 312, providing for the assessment of a property tax at the beginning of each 15-year cycle. It continues to be used in ecclesiastical contracts. The second opening, which occurs immediately below the eagle, is marked "Cyc. Sol." (cycle of the sun). This cycle takes a period of 28 years, after which the days of the week once again fall upon the same days of the month as they did during the first year of the former cycle. There is no relationship with the course of the sun itself, but was invented for the purpose of determining the dominical letter which designates the days of the month on which the Sundays occur during each year of the cycle. Since cycles of the sun date from 9 years before the Christian era, it is necessary to add the digit 9 to the digits of the current year and then divide the result by 28. The quotient is the number of cycles which has passed, and the remainder will be the year of the cycle answering to the current year. The third opening on the riband is labeled "Num. Aur." (golden number). Meton, an astronomer of Athens, discovered in 432 B.C. that after a period of 19 years the new and the full moons returned on the same days of the month as they had before, and this is called the cycle of the moon. The Greeks were so impressed with this calculation that they had it inscribed in letters of gold upon stone, hence the golden number. The First Council of Nicaea in A.D. 325 determined that Meton's cycle was to be used to regulate the movable feasts of the Church.

Immediately above the chapter rings is an opening through which the orb of the sun is visible.

THE CHAPTER-RING ASSEMBLY

In a separate chapter in his second volume, entitled "Descriptio Authomatis Summa totius Operis Mechanici" (Description of the Automaton—Summary of the Complete Mechanism), Father Borghesi provided a description of the functions of the various indicators, prefixing it with the short poem shown in figure 18. He then continues:

In the middle of the frontispiece, as at the center of the universe, the terraqueous globe of the week revolves, with a daily motion turning from right to left, bringing with it from the round window the coming day and at the circumference the circle of hours common to the sun, to the moon, to the fixed stars, to the head and tail of the dragon, and to the raging sea.

The second circle revolves the synodic-periodic measure of the raging sea, the days of the median lunar-synodic age, the signs and individual degrees of the signs of the distance of the moon from the middle of the sun within the time of 29 terrestrial revolutions, hours 12.44.3.13. This circle revolves likewise from right to left around the center of the earth. In this second circle, another little orb revolves, bringing with it the epicycle of the moon, in which the little circle of the moon (whose illuminated middle always faces towards the sun), running from left to right through the signs of the anomaly; within 13 revolutions of the earth, hours 18.39.16. It descends from apogee to perigee and in just as many others it returns from perigee to apogee, to be carried down thus to true, back and front from the longitude and distance from the sun and from the middle of the earth.

The third circle (on which I have tried to indicate astronomically-geometrically in their places, the degrees of lunar latitude both in the south and in the north, and some fixed stars, those, namely, which can be separated by us from the moon which goes between) from left to right turns around the center of the earth, stretching out the head and tail of the dragon, on the inside above the second circle for noting and measuring the sun (but I should rather say the earth), and the eclipses of the moon, within 346 revolutions of the earth, hours 14.52.23.

The fourth circle, in which the heaven of the fixed stars, reduced to the correct ascent of our times, the signs of the zodiac and the individual degrees of the signs, the months of the year and the single days of the month can be seen, likewise makes its journey around the earth from left to right in 365 terrestrial revolutions, hours 5.48.56.; that is, within a median astronomical year. Above this annual orb, the sun, in its small epicycle, gliding through the 12 signs of the anomaly, within the space of 182 terrestrial revolutions, hours 15.6.58., from left to right, falls from apogee to perigee; and, within the same time, rises from perigee to apogee, and brings with it, the index, namely its central radius, inhering to the axis of the equatorial orb and cutting the four greatest circles from the center.

When the sun has been moved around, Iris shows from six windows the era, that is, the current year. Two winged youths take their place next to Iris, carrying the Julian period: namely, the Roman indiction, the cycle of the sun and the golden number, on a leaf of paper held between them. The imperial eagle stands out on top (as if added to the frontispiece) carrying on its breast the dominating planet and in its talons the ecclesiastical calends (that is, the dominical letter and the epact).

ATTACHMENTS FOR ADJUSTMENT

Two attachments, in the form of small superimposed dials are situated at the base of the dial plate, at either side and immediately below the fourth chapter ring. In his second volume, Father Borghesi stated that they "are not moved from inside the clock, but the one at the right [inscribed concitat and retardat] serves for loosening [accelerating] and tightening [retarding] time; that is, the reins of the perpendicular."

In other words, the purpose of this attachment is for adjusting the pendulum to make the clock operate fast or slow. The second attachment, which appears at the left, and which is inscribed "Claudit" (close) and "Aperit" (open) serves the purpose of "… preparing the mechanism in a moment, as swiftly as you wish, for sustaining the astronomical experiments of which you will hear later; when these things have been done, it restores the mechanism to its natural motion at the same speed."

This adjustment relates to the final section of Father Borghesi's second book, entitled "Chronologo-Astronomicus Usus Authomatis" (Chronological-Astronomical Use of the Automaton), which is translated from the Latin in its entirety:

With one glance at this automaton, you can quickly answer these questions: What hour the sun shows, the moon, any fixed star, the head and tail of the dragon. Is the sea swelling with periodic heat [at high tide?] or is it deflated [low tide], or quiescent? How many days is it from mean new moon or full moon? By how many signs and degrees is the moon distant from the sun, and from its nodes? What sign of the zodiac does the sun occupy, the moon, the head and tail of the dragon? Is the sun or the moon, in apogee or perigee, ascending or descending? What is the apparent speed of the sun and of the moon? What is the apparent magnitude of the solar and lunar diameter, and of the horizontal parallax of the umbra and penumbra of the earth? What is the latitude of the moon? Is it north or south? Does the moon hide [occult eclipse] any of the fixed stars from the earth dwellers, and which of these does it obscure? Is there a true new or full moon? Is the sun in eclipse anywhere on earth? What is the magnitude, and the duration of this eclipse, with respect to the whole earth? Can it be seen in the north or in the south? Is the moon in eclipse? Total or partial? Of what magnitude, etc.? What limb of the moon is obscured? How many years have passed from a given epoch? Is this year a leap year, or a common year—first, second, or third after leap year? What is the current month of the year, and what day of the month and of the week? Which of the planets is dominant? What days of the year do the various feasts fall on, and the movable feasts during the ecclesiastical year? And many other similar questions, which I pass over here for the sake of brevity.

Besides, this device can be so arranged for any time whatsoever, past or future, and for the longitude of any region, and can be so manipulated by hand, that within the space of a very short time there can be provided in their proper order, the various orbits of the luminous bodies, their alternating eclipses, as many as have taken place through the course of many years, or even from the beginning of the world; or those that will be seen as long as the world itself shall last, with all their attendant circumstances (year, month, day, duration, magnitude, etc.). All these can be seen with great satisfaction of curiosity and of learning, and hence with great pleasure to the soul. In the meanwhile, the little bells continually play, at their proper, respective times. So that, all exaggeration aside, a thousand years pass, in the sight of this clock, as one day!

I am aware of your complaints, O star-loving reader—that my description is too meager and too succinct. Lay the blame for this on those cares, hateful both to me and to you, more pressing, which forbid me and deprive you of a methodical explanation of the work.

THE CLOCK MOVEMENT

Father Borghesi specified that the entire mechanism was equal in weight to a seventh part of a Centenarii Germanici, a Germanic hundredweight. This is probably the Austrian centner which is equivalent to 123.4615 pounds. Therefore, the clock mechanism weighs approximately 17.6 pounds.

The clock operated for a hundred days and more at a single winding, according to Father Borghesi, and by means of a pendulum with a leaden bob weighing 60 Viennese pounds, attached at a height of 5 feet. Father Borghesi stated the weight of the pendulum to be 60 librarum Viennensium, but the Viennese libra does not appear among the weights of the Austrian Empire. However, using the average libra, an ancient Roman unit of weight equal to 0.7221 pound, it may be assumed that the driving weight should be approximately 45 pounds.

Father Borghesi, however, does not venture to provide any description whatsoever of the movement of his second clock in his book. He gave the following reasons:

But beyond this, I entirely omit [a description of] the further apparatus of the very many wheels, etc., inside the clock which carry on its functions, lest I become too verbose for some persons. To explain more thoroughly the internal labyrinth of the entire mechanism, from which the movement of the circles or heavens, etc., are derived, would seem to entangle in too many complicated perplexities…. Therefore, that I might not delay longer, and perhaps to no purpose, I have thought it better to leave the whole work to the proportionate calculus of the arithmeticians and the technical skill of mechanics. If they have any desire to construct a similar mechanism, they will follow the aforesaid motions of the heavens, etc., not only by one means alone but by many, more swiftly through thoughtful study than by any amount of instruction.

For whoever is well versed in the theory of calculus and sets to work at any given project, will discover any desired motion by a thousand and more ways, by one or another gearing of wheels; which an industrious mechanic will carry out in actuality and without too much difficulty. Nor is there any reason for anyone to be discouraged, so long as he is not disgusted by the amount of labor for there is nothing truer than the old saying "The favorable gods grant everything to the assiduous laborer."

Nay, further, even this little work itself can be improved on and surpassed by new inventions. Otherwise that other old adage, almost as old as the world, would prove false, "What you have found already done, you can easily repeat, nor is it difficult to add to what has already been invented." Relying on this principle, I have already conceived some new things to be added to the present little work.

Figure 17.—Movement of Borghesi clock viewed from the right side, with details of chiming mechanism.

THE BELLS

There is a discrepancy between Father Borghesi's written description in his second book of the number of bells and those which currently exist in the clock. At the present time, there are two sets of bells attached to the upper part of the movement. While Father Borghesi indicated that there were two sets of bells in the clock, he described the first set by stating that:

… there are three bells inside the clock: The largest, when struck by a little hammer at each mean new moon, signifies the new moon. The smallest indicates in the same way the full moon at the time of the mean full moon, by automatic sound. When on the equatorial earth, the sun appears anywhere in eclipse, two bells (the largest and the medium) sounding together automatically, announce that eclipse at the time of the mean new moon. (I think it is evident that eclipses of the sun occur at new moons and eclipses of the moon at full moon.)

When the moon is eclipsed, the smallest and the medium bells, simultaneously and automatically, announce the event to the ear at the time of the mean full moon. Besides, at the proper time and automatically, the largest of these bells announces the current solar hour and the smallest bell strikes the quarter hours.

In the clock today, the first set consists of a smaller bell fixed within a larger one. It is presumably these bells that indicate the eclipses and also strike the hours and quarter hours. A pull cord attached to the striking mechanism repeats the current hour and quarter hours at will. The second set consists of nine meshed bells struck with individual hammers operated by means of a pinned cylinder as in a music box. On the hour, the chimes play one of two melodies, which may be changed at will. While not identified, these appear to be Tyrolean folk melodies. The largest of this set of bells is dissimilar to the other chimes, and may be the third bell described by Father Borghesi to signify the new moon.

CHRONOGRAMS

One of the most curious aspects of the second clock produced by Father Borghesi and Bertolla, as well as of the second published volume, is the presence of chronograms which occur repeatedly on the clock dial and throughout the Novissimum Theorico-Practicum Astronomicum Authoma from the title page to the end of the book. Interestingly enough, Father Borghesi did not utilize this device even once in his first little book.

Figure 18.—A chronogram in the text of Father Borghesi's second volume, indicating the year 1764. The poem is translated as: "In the Mount of 'Anáuni,' the inscrutable heavens are led, You learn from these all the labors of the sun and the moon. Here you are shown and hear the conjunction of the moon: And a bell brings to the ears by its sound, all eclipses."

Webster defines a chronogram as an inscription, sentence, or phrase in which certain letters express a date or epoch. The method used by Father Borghesi for forming chronograms was a simple one. He used combinations of uppercase and lowercase letters in two sizes in the inscriptions on the clock dial and in his writings. At first this curious combination in the inscriptions on the dial plate was a source of considerable speculation. The extremely fine quality of the engraving and artistry was such that these combinations could only be deliberate in nature and not the accidental whims or accidents of the engraver. Accordingly, they must be chronographic in intention. Such proved to be the case.

Borghesi used the larger size of uppercase letters to form the chronogram, and each chronogram was complete within a phrase or line. He accomplished this by using for this purpose those letters of the alphabet which form the Roman numerals. The uppercase letters found within words are copied off in the order in which they appear in the inscription or phrase. These are then converted into their numerical equivalents, and totaled. Taking the uppermost inscription on the clock dial as the first example:

FranCIsCVs I sIt pLan. DoMInator aeternVs

The letters which are intended to form the chronogram are:

C I C V I I L D M I V

100 1 100 5 1 1 50 500 1000 1 5

These figures added together total 1764.

The second inscription on the clock dial which forms a chronogram is

LaVs saCrosanCtae TrIaDI VnI Deo, et DeIparae

L V C C I D I V I D D I

50 5 100 100 1 500 1 5 1 500 500 1 = 1764.

The third inscription required a little more planning, because of its greater length. Accordingly, Father Borghesi divided it into nine parts, each of which is separated from the other by means of asterisks. Each of the nine parts of the inscription formed a chronogram which, in every instance, totals to the date 1764, the year in which the second clock was completed. The same procedure was followed with the inscriptions in the lower left and the lower right corners of the dial as well as with the maker's inscription within the central disk. This inscription is

BVrghesIo DoCtore, et BertoLLa LIMatore AnnanIensIbVs

V I D C L L L I M I I V

5 1 500 100 50 50 50 1 1000 1 1 5 = 1764.

The inscriptions within the chapter ring are not utilized for chronograms, however. It is apparent that Father Borghesi was required to make a most careful selection of the texts for his inscriptions in order that none of the phrases included any additional letters which formed Roman numerals than would total to the date he desired to indicate, namely, 1764. Where it was necessary, he employed an asterisk to separate parts of texts so that each would produce the same total. Any letter that did not form a Roman numeral, even if capitalized or used in a larger size, did not interfere with the formation of the chronograms.

In spite of his ingenuity in designing a text which would include only such of the letters representing the Roman numerals which would provide the chronograms for 1764, Father Borghesi experienced some difficulties, particularly in place names. He accordingly changed them in order to avoid the inclusion of letters that would have disturbed his totals. Examples are MEGGL instead of MECHL, which had an extra C, and RVNNO instead of RVMO, which had an extra M.

PUBLISHED DESCRIPTION OF THE SECOND CLOCK

When the clock had been completed and proved to work successfully, Borghesi once more reduced a description of the clock and its function to published form in a second little volume published by Monauni. This second work was also in Latin, the title of which is translated as The Most Recent Theoretical-Practical Astronomical Clock According to the Equally Most Recent System of the World. As with his first book, Father Borghesi devoted a number of pages to a preface addressed to the reader, which is translated from the Latin:

This mechanical instrument was far from being ready for public notice. A great deal of time and work remained to produce a machine of this new system from the very foundations; then, by a most accurate calculation to bring the motions of many wheels up-to-date with the most recent astronomical observations; and, finally, to fashion it with the craftsman's file, often enough with a weary hand. All this work I had performed eagerly, so that, while in my room, I might contemplate leisurely, both day and night, the true face of the heavens and the seas unobscured by clouds, even though I had no astronomical equipment. But, then I remembered that, in my book on the first clock, I had promised a description of a new (at least, as far as is known to me) clock. Moreover, friends with astronomical interest, who took part in the oft-repeated astronomical experiments concerning this clock, persuaded me that the intellectual world would enjoy having a greater knowledge and a description of this work. However, it was not only the promises nor the desires of many which moved me to write this work, but I also thought it was necessary to set forth, before the description of the clock, an exposition of the astronomical system according to which this clock was constructed, so that the complete work would be evident to all. I was concerned about making this timepiece more acceptable and more understandable to those people who are far distant and unable to see it, so that this present exposition would obtain credulity among all. I could find no better method than to set forth for the reader the theory of the universe which I figured out after many sleepless nights.

In testing this theory day after day, it not only appeared to be complete, and true, but each day it appeared more conformable to reality; it captured my mind in such a way that I finally adhered to it. I desired, while I lived, to erect this work as a monument to the theory. To do this, I digressed a bit from the true-to-life pattern to the mechanical order so that I could transfer all the movements of the heavens, etc. (which I enjoyed thinking about more), to the plane surface of the clock's face. In this way, the ecliptical spectacles of the stars, etc., would appear at their proper times clearly before the eyes of the viewer. I could also avoid many difficulties which otherwise, perhaps, even the hands of the most skillful craftsmen could never solve.

Figure 19.—Movement of the Borghesi clock, viewed from the rear, showing rear of dial plate.

Figure 20.—Title page of Father Borghesi's second book. The translation in its entirety is: "The Most Recent Theoretical-Practical Astronomical Clock According to the Equally Most Recent System of the World. Author: Francesco Borghesi of Mechel of Anáuni * Priest of Trent, Doctor of Philosophy * (The System of the Clock) Ingeniously connected to new theoretical laws published 1764: and the constructor, Bartholomeo Antonio Bertolla of Rumo, similarly from Anáuni * who skillfully produced this work * in this same current year of Our Lord * which is the year 5713 [sic] since God created this earth. (Trent: From the Printshop of Giovanni Battista Monauni, With Permission of the Superiors.)" (Title page reproduced by courtesy of the Biblioteca della Citta di Trento.)

You ought to know, therefore, that as a result of my nightly meditations, I have rejected, after much consideration, all the explanations of the universe thus far published. All other theories of the make-up of the universe, however admirable, and however many there are, turn the sun and earth around in an ecliptic in an annual movement. Thus, Philolaus was the first to move the earth from the center of the universe and move it through the void; afterwards, Aristarchus of Samos and then Copernicus moved the earth with the moon. The Egyptians, as well as Pythagoras, Ptolemy, Tycho, Riciolus, Longomontanus, etc., thought that the sun moved through the degrees of the ecliptic each year. But I attributed this movement to neither earth nor sun for the movement of both is only apparent. I did not vainly surmise the annual equilibrium in all astronomical observations to be from the daily movement of the same axis moved at the poles of the heavens. Nor, in like manner, is there a better way to satisfy physical experiments. To you, then, most cultured reader: If you, perhaps, can make any use or draw pleasure from this most faithful description of my new theory and the mechanical instrument, refer it first to God on High from whom is everything that is best, and then to those avidly awaiting this little work. Lastly, if you find any statement less fitting; in your humanity, do not disdain to excuse it.

Borghesian Theory of the Universe

In Father Borghesi's second volume, there is a separate chapter entitled "An Exposition of the Latest Theory of the Universe." This follows the introduction to the reader, and in it Father Borghesi proposed:

That you might rightly conceive my new system of the world and mechanically, as it were, construct it, imagine for yourself, beneath that most happy seat of the Blessed and above all other heavens, a kind of spherical convexity, everywhere equidistant from the center of the earth, and endowed with absolutely no motion.

On the inside, at two points diametrically opposite each other, this convexity has two most sturdy poles (to speak mechanically), projecting towards the center (which you call the poles of the heavens), and the largest immobile semicircle, in some manner is drawn from the center of one pole to the center of the other. This semicircle in the middle, namely at a point equidistant from each pole, is thought to be secured by some sign, for example, by that "o," for arranging more perceptibly the seat of the sun (as will be shown later). This much must be conceived first.

You must understand that imposed on these poles is the first mobile [Primum Mobile], everywhere convex, and divided, into 12 equal parts [Dodecatemoria], by the 6 greatest circles, intersecting each other at the centers of the poles. Then it is divided by another equally great circle, everywhere equidistant from the poles, into two hemispheres. One hemisphere of 12 parts, proceeding in order from west [setting] to east [rising] should be assigned the respective signs of the zodiac; that is, one to Aries, the next to Taurus, and so on, etc. The circle which cuts those 12 parts transversely in the middle, you call the ecliptic. Then, these capital spaces of the Primum Mobile are subdivided by degrees, minutes, etc., both in longitude and in latitude, so that this heaven represents a kind of great spherical net, extended to capture the longitude and latitude of the stars, and Mobile on the aforementioned poles. Note, however (and this is almost the leading point of the system), in that circle of longitude which divides the sign of Gemini from Cancer and Arcitenens [Sagittarius] from Capricorn, you must conceive two points, directly opposite each other and removed about twenty-three and a half degrees from the poles: Boreal [the northern] between Gemini and Cancer; Austral [the southern] between Sagittarius and Capricorn. These two points by some power (imagine it is magnetic power), equal between them, hold the terraqueous orb suspended in the middle, by acting on the axis of the same orb (imagine it is iron) in such a way that the earth is continually drawn to those two points as to two opposite centers. It is never nearer to one, for as it is about to move towards one, the opposite power is constantly drawing it back. Thus, both those points and the axis of the earth are always held in one common line, wherever those points happen to be carried by the rotation of this heaven.

Again, it is necessary for you to conceive in this heaven, first, two great circles, bisecting each other at right angles in the centers of these two magnets. One of these circles, passing through the first point of Aries and Libra in the ecliptic, is called equinoctial colure: the other circle, passing consequently between the first point of Cancer and Capricorn, is called solstitial colure. Beneath these are likewise imagined many other great circles, in the centers of the magnets dividing crosswise in the shape of an "X." But if, receding from these magnets, you describe circles (parallel to each other and ever greater and greater, up to the greatest circle which you will perceive is called the equator), equidistant from each magnet and obliquely splitting the ecliptic in the equinoctial colure, you can then behold a great, new, woven net in this heaven of the Primum Mobile. This net most beautifully expands to extract the straight ascent and descent of the stars, etc., from the vast ocean of the heavens, catching the straight ascent in the greatest circles and, in other unequal circles, parallel to each other and obliquely cutting across, most safely catching the descent.

GLOSSARY

Anomolia or anomaly, is the angular distance of a planet from its perihelion (that point of the orbit of a planet which is nearest to the sun) as seen from the sun.

Aequinoctium or the equinox, is the time in which days and nights are equal in the space of hours. There are two equinoxes: the spring equinox—c. 8 calends of April in the sign of Aries; and the fall equinox—c. 10 calends of October in the sign of Libra.

Aeras is derived from aera, aerae, which originally meant a given number, usually used in regard to money. The word was later extended to mean a number used in any calculation, and finally it came to mean a certain time from which subsequent times were counted, e.g., Anno Domini, after the Birth of Christ.

Coluri or the Colures, which are two circles in the heavenly sphere, passing through the poles of the world and cutting each other at right angles: the one passes through the equinoctial points of Aries and Libra and is called Colurus Aequinoctiorum or equinoctial colure; the other touches the solstitialia of Cancer and Capricorn and is called Colurus Solstitiorum or solstitial colure. They are called Colurus, which is translated as "mutilated tails," for the part which emerges in the Antarctic is not visible and is quasitruncated.

Ecliptica or the ecliptic, is an imaginary line in the heavens in which the sun was supposed to have performed its annual course.

Epicyclus or epicycle, is a small orb which, being fixed in the deferent of a planet, is carried along with its motion and yet, with its own peculiar motion, carries the body of the planet fastened to it round about its proper center.

Iris or the rainbow. In mythology, Iris was the daughter of Thaumatis and Electra, messenger of Juno of the goddesses and Jove of the gods.

Solstitium or the solstice, is that time when the sun seems to stand still for a short time: when the sign of Cancer enters the month of June (equivalent to the summer solstice, when the sun begins to recede from us); and when the sign of Capricorn enters the month of December (equivalent to the winter solstice, when the sun begins to accede to us).

Immediately below the Primum Mobile place the heaven of the fixed stars (and, that the idea might be clearer), revolving separately on the same poles on which the Primum Mobile revolves. Through this heaven, the filaments of the little nets, etc., seem to the eyes of you on earth as if they shine. In this heaven, you should conceive in their fixed places, the fixed stars, a proportionate, inviolable distance from each other, and, indeed, if you will, the heavenly images, etc., depicted, and all carried along at the same time with their heaven by one motion.

Conceive a straight line running from the center of the earth to that sign "o" noted in the semicircle of the supreme immobile heaven. On this line, greatly below the heaven of the fixed stars, place the center of the solar epicycle, holding an area in common with the ecliptic and subject to absolutely no motions, but at such a distance from the center of the earth that the semidiameter of the earth has little, if any, proportion with the distance of the solar epicycle from the earth. Around the sun, moving continually in this epicycle (its immobile palace) through the degrees of the anomaly, you can revolve, with motions proportionate to the system, the five planets: Mercury and Venus (the nearest barons of the sun), then Mars, Jupiter and, most remote, Saturn, with its respective satellites, etc., eccentrically surrounding the earth itself and the moon in their immense ambit and wandering by their proper motions through the zodiac.

Nevertheless, not far from the earth you should imagine fabricated, as from most refined crystal, the heaven of the moon everywhere equidistant from the center of the earth and revolving separately on the same poles (prolonged even to this place) on which the Primum Mobile and the heaven of the fixed stars revolve. In the middle of this, that is, in some point equally removed from the poles, you place the center of the lunar epicycle, movable also by the common rotation of the lunar heaven. I refrain from the other movements of the moon in latitude, etc., as also those of the five planets, etc., which the theory in no way excludes, lest by a variety of congested motions explained too abundantly, either you might be confused about the fundamental concept of the system or, while adorning the theory and trying to embellish the least things more widely, you might reject also the things which are capital.

Here you already have the whole machine, but still inert and to be animated for the first time by motions accommodated to the system. Nevertheless, before I assign motion to the individual parts of the world, so that the thing might later appear more clearly to you, I arrange all things thus: first, as if by hand, I turn the Primum Mobile until the Boreal magnetic point comes to the level or the area of the semicircle described in the supreme immobile convexity; then I turn the heaven of the fixed stars until, for example, the heel of Castor (a star of the third magnitude), almost in the ecliptic and indeed in our time not far distant from the solstitial colure, likewise falls nearly at the level of the aforesaid semicircle. Later, I turn the lunar heaven until I bring the center of the lunar epicycle to the same level. Then, I turn the earth until some predetermined city, for example, Trent, situated in the northern zone with a latitude of about forty-six degrees, is brought to the oft-mentioned level.

From things arranged in this way and from what has gone before, it is evident (with the motions of the luminaries in epicycles left out, however, lest you be distracted by the explanation) that at Trent, just as in the whole northern hemisphere, it is the summer solstice; and, conversely, in the southern hemisphere, it is the winter solstice. The reason is because the northern magnetic point together with the northern half of the earthly axis is at its highest point towards the sun, immovably residing in a line sent through the level of the highest semicircle; and, conversely, the southern magnetic point with the corresponding half of the axis is most removed from the same. It further follows, that noonday and the new moon coincide, and the heel of Castor almost reaches the summit, etc.

Now, beginning from this hypothetical situation of the whole world as from the root of the motions, I move all things in their circles so that the earth turns on its axis with a revolving motion from west to east in each 24 hours of median time. The lunar heaven completes one circle around its poles likewise from west to east in the time of 29 terrestrial revolutions, hours 12.44.3.13.1. The sphere of the fixed stars on the same poles revolves once from east to west within 365 revolutions of the earth, hours 6.9.29.1. The Primum Mobile on the poles (common to the heaven of the fixed stars and the heaven of the moon), is moved once in the same way from east to west, a little faster, however, than the heaven of the fixed stars, yet within 365 revolutions of the earth, hours 5.48.56; that is, within a median astronomical year.

Now, behold for yourself a new world supported on new poles and provided with new motions and laws. Now you, reader and lover of the stars, turn it, and revolve it as long as it pleases you, and compare it astronomically and physically with the Copernican or the Tychonian systems or with whatever one pleases you more, and judge which one seems more consonant with nature when all things are examined. But if you aren't able to reconcile this theory with some astronomical observations or physical experiments and think it should be eliminated from the group of theories, see that I might know this while life is still my companion, so that I might think with you, if this is possible. Also, so that, in gratitude for the detected or perhaps hidden error, I might speak or write, and you won't have to shout in vain in bold ridicule and with no applause after the fleeing shades of the dead and the mute ashes. But, if you object that the daily motion of the revolving earth and the annual motion of its whirling axis do not sufficiently agree with certain texts of Sacred Scripture, and if those things which the Copernicans and the Longomontanists say do not convince you, then reject my whole system as an old wives' tale.

Last Years

There is a break in the story of Borghesi and Bertolla for the next five years. The second clock may have been the last project on which the priest and the clockmaker worked together, for very good reasons. The two clocks must have represented a considerable financial investment in materials and in time, and neither of the men was in sufficiently affluent circumstances to undertake the luxury of such a hobby without some form of recompense. The publication of the two little volumes must have also been done at Father Borghesi's expense. The income of the parish priest in a small mountain village could not have been equal to the relatively great costs of the projects that had been completed. It seems probable that the priest attempted to sell his clocks to a wealthy patron, perhaps the Baron of Cles, or he may have attempted to obtain some form of recompense for the continuation of his research. However, no records can be found of such patronage if it existed. If Borghesi had received financial assistance while the projects were in progress, he would certainly have made adequate mention of the patron's name and assistance in one or the other of the two volumes which he published.

The next record relating to Borghesi which has been found is the description of a letter written by an anonymous mathematician late in 1768 or early in 1769. It was 28 pages in length, written in Latin, in the form of a reply to the writer's brother, on the subject of the clock invented by Borghesi. It consisted primarily of a criticism launched against Borghesi's first little volume published in 1763.

The anonymous letter is without date, place, or signature. This writer claimed that Father Borghesi had made many errors in his book, presumably in the description of the clock's functions, and in the basic theories upon which the priest had predicated his research. No complete copy of the letter's text has been found for study, although it is described at length in Tovazzi's Biblioteca Tirolese. Tovazzi noted that four copies of the letter existed at that time, and that he personally had filed one in the Biblioteca di Cles in Trent. However, every attempt to locate a copy at the present time has been unsuccessful.

If the anonymous letter was brought to the attention of Father Borghesi, it must have introduced a disturbing note into his life and cost the priest many unhappy moments. He was not, however, dissuaded from his preoccupation with horology. Several years later, in 1773, Father Borghesi was working on yet another astronomical clock, this time presumably without the assistance of Bertolla. This third clock was reported by Tovazzi to have been "of minimum expense but of maximum ingenuity."

No subsequent information relating to it has come to light, and there is no record that it was actually completed.

Again there is a period of silence in the life of Father Borghesi which no amount of research has yet been able to pierce. Whatever the circumstances may have been, it is reported by several of the sources noted that both the first and the second clock did, in fact, become the property of the Empress Maria Theresa in Vienna. The presentation was made sometime during the period between the completion of the second clock in 1764 and the year 1780. There is some discrepancy in the contemporary accounts as to whether Father Borghesi presented one or two clocks to the Empress, but all the sources with but one exception record that both clocks were acquired by the Empress.

It is doubtful that Father Borghesi had originally intended to give his clocks to the Empress at the time that they were made, for he would most certainly have made some mention of such an intention in the two little volumes which he published about them. If he saw the letter published by the anonymous mathematician in late 1768 or 1769, it is possible that he decided to make the presentation in expiation of his sense of guilt for the amount of his time which the creation of the timepieces had consumed. On the other hand, it is just as possible that Father Borghesi may have forwarded copies of his two little volumes to the Imperial Court at Vienna, and that the Empress expressed a desire to acquire the clocks.

Father Tovazzi states that in 1780 "the clock invented by him [Borghesi] was preserved in Vienna, Austria, at the Imperial Court from which the inventor was receiving an annual pension of 400 florins." No records in the Palace archives relating to the clock have yet been found, nor records of payment of an annuity to Father Borghesi. However, a more exhaustive investigation of the Furniture Depository of the Imperial Court may bring forth related records. It was the implication in Father Tovazzi's account that the second clock had been presented to the Empress prior to the publication of the anonymous, critical letter in 1768 or 1769. He believed that it was envy of Father Borghesi's ingenuity, fame and financial benefit that had caused the anonymous mathematician to publish his letter, for Tovazzi asked "Who would have encountered opposition to such a marvel? Envy is not yet dead, and has always reigned."

This last-mentioned theory about the presentation may be the most likely one. Some evidence may be found in the second clock itself which bears out this assumption. The multiple chapter ring, with its many inscriptions, is engraved and silvered in a relatively crude manner, presumably by Bertolla himself. The main dial plate, however, which is of gilt brass, is engraved with the utmost skill by one of the great masters of the art. The inscription below the Imperial Hapsburg eagle relates to Francis I, Emperor of the Holy Roman Empire. It is entirely possible that although Father Borghesi originally had no intention of giving the clock to the Emperor or the Empress at the time that it was made, he later changed his mind. Accordingly, he may have commissioned a master engraver, possibly in Trent or in Vienna itself, to produce a dial plate which would be of such a quality as to be worthy of the Emperor himself. If so, this was done shortly after the clock was completed, for the Emperor died in August of the following year. Perhaps by the time that the clock was ready, the Emperor had already died, and Father Borghesi gave the clock instead to Maria Theresa without revising the inscription.

The acceptance of the clocks by the Empress, and the annuity which was his reward, would have constituted considerable honor even for one of the foremost clockmakers of the Empire, but for a humble parish priest in a little village, such notable Imperial recognition was overwhelming. Possibly as a result of it, a change was noted in Father Borghesi in the next few years. His conscience began to bother him, and he began to question whether he had done right in spending so much of his time and thought on his horological research. He became more and more confused in his own mind. Had he spent too much time in mechanical studies to the neglect of his ecclesiastical duties? If this had been the case, he had committed the most grievous sin.

Exaggerated though these thoughts may appear, they were undoubtedly of the most critical importance to the middle-aged priest. His mental turbulence and confusion increased daily, and it soon became apparent to others around him. By June 1779, he was completely in the grip of his obsession, and his parishioners began to whisper amongst themselves that their pastor was being tortured by the devil. They were unable to help him, and he became more and more preoccupied with his problem. The years passed slowly as the pastor became more vague and more tortured by his conscience.

There probably was continued contact between Father Borghesi and Bertolla for at least some time after the development of his illness. Bertolla had retired from active work, but continued to pursue his interests in his clockshop as much as his health and advanced years permitted. A clock which he made at the age of 80 survives and is described and illustrated in the following section on "The Clocks of Bartolomeo Antonio Bertolla." Finally, on January 15, 1789, Bertolla passed away and Father Borghesi was left alone, deprived of the companionship he had enjoyed with the older man for the past two or three decades. One of Bertolla's nephews continued to work in the master clockmaker's workshop, but there did not appear to be any association between the younger man and Father Borghesi.

At last, in 1794, Father Borghesi lost his sanity completely, and he was forced to relinquish his pastoral duties to a curate. For the remaining eight years of his life, he continued to live in the rectory of the little parish church in Mechel where most of his life had been spent, his needs undoubtedly attended by the parishioners he could no longer serve. During this period, until his death at the age of 79 on June 12, 1802, Father Borghesi lived on, oblivious of those around him. Seemingly, he retired to another world; perhaps to that universe which he had tried to reproduce in his second clock.

The Clocks of Bartolomeo Antonio Bertolla

Figure 21.—Tall-case clock by Bertolla in the Episcopal Palace in Trent, made for Bishop Cristoforo Sizzo di Noris. A striking and repeating clock with lunar phases. (Courtesy of Museo Nazionale della Scienza e della Tecnica, Milan.)

The ingenuity displayed in the Borghesi clock by its constructor, Bartolomeo Antonio Bertolla, requires a consideration of the other examples of his work that have survived. The most important of his clocks are probably the one in the Episcopal Palace at Trent and another made for the Baron of Cles.

The one which survives in the Episcopal Palace to the present time, is extremely tall and is housed in an elaborately decorated narrow case of black or ebonized wood approximately 9 to 10 feet in height. The upper part of the case is decorated with elaborately carved and gilt rococo motifs. The movement operates for one year at a winding, indicates and strikes the hours, and shows the lunar phases. It has an alarm, and will repeat the strike at will, indicating the number of the past hour and the quarters. The gilt brass dial is decorated with silver-foliated scrollwork in relief at the corners, inside the chapter ring, and within the broken arch. Featured above the chapter ring is the coat of arms, executed in silver, of the patron for whom the clock was made, Cristoforo Sizzo di Noris. Di Noris was Bishop of Trent for 13 years, from 1763 to 1776.

The clock which Bertolla made for the Baron of Cles is a tall, narrow, case clock of ebony or ebonized pearwood which is approximately 9/2 feet in height. The decoration of the case is considerably more conservative than the one made for Di Noris, but the black wood is decorated with silver trim and carved designs in the wood itself. The dial is decorated with silver scrollwork and spandrels within and around a raised chapter ring. The clock operates for one month at each winding, has an alarm, indicates and strikes the hours, and will repeat the quarters. This handsome timepiece is still in the possession of the descendants of the Baron of Cles.

According to Pippa, certain characteristics become apparent in a study of the surviving clocks by Bertolla. The tall-case clocks are narrow and range in height from 7/4 feet to 10/2 feet. The cases had this excessive height in order to obtain the greatest fall for the month and year movements which Bertolla constructed. For the weight assembly, he substituted a drum wound with a key at the point of the driving wheel in place of the customary pulley. The addition of an intermediate wheel augmented the drop of the weight.

Figure 22.—Interior of Bertolla's workshop, showing detail of ceiling. (Courtesy Museo Nazionale della Scienza e della Tecnica, Milan.)

Figure 23.—Interior of Bertolla's workshop, showing the main workbench and the collection of clockmakers' tools. (Courtesy of Museo Nazionale della Scienza e della Tecnica, Milan.)

Figure 24.—Fusee cutter used by Bertolla. Now in the collection of the Museo Nazionale della Scienza e della Tecnica, Milan.

Figure 25.—Interior of Bertolla's workshop, showing details of paneling and floor case with Bertolla manuscripts. (Courtesy of Museo Nazionale della Scienza e della Tecnica, Milan.)

Bertolla's movements were solidly constructed from well-hammered brass and iron. He favored the recoil anchor escapement in his clocks and the Graham dead-beat anchor escapement with a seconds' pendulum. The escapement was not always placed in the traditional location in the upper center between the plates. Bertolla occasionally displaced the pendulum to one side, to the lower part of the movement or placed it entirely between two other small plates.

He utilized every type of striking work, including the music-box cylinder common in the clocks of the Black Forest and the rack and snail. Bertolla most frequently employed the hour strike and grand sonnerie. He often used a single hammer on two bells of different sound with the rack and snail. An example of this type is the clock he produced at the age of 80. To achieve the necessary axis of rotation for the hammer, which is perpendicular to the plate when it strikes the hours, it moves to an oblique position and displaces one of the two long pins in an elongated opening.

Bertolla's dial plates were generally well executed, with a raised or separate chapter ring applied to a brass or copper plate, such as a copper-plate repoussé and gilt with baroque motifs, or upon a smooth brass plate with spandrels of repoussé work usually of silver, in relief and attached. The engraving of the chapter rings was excellent. The hands were well executed in steel or perforated bronze, and occasionally of repoussé copper; gilt was applied to the hands made of forged steel.

Figure 26.—Dial plate of a brass lantern clock made by Bertolla, found in his workshop after his death. (Courtesy of Museo Nazionale della Scienza e della Tecnica, Milan.)

Figure 27.—Movement of a brass lantern clock made by Bertolla. (Courtesy of Museo Nazionale della Scienza e della Tecnica, Milan.)

In the course of time, Bertolla's home workshop passed from one generation to another within the family. Inevitably, it underwent many modifications until the only original part of the building that remained intact from Bertolla's time was his clockshop.

Within the last few years, the workshop room was acquired complete with contents from Bertolla's descendants, and installed in the Museo Nazionale della Scienza e della Tecnica in Milan as an exhibit of a typical 18th-century clockmaker's shop. The original workshop was dismantled in Mocenigo di Rumo and completely rebuilt in the museum, including the walls, ceiling and floor. The paneling and woodwork of the walls and ceiling, which have been preserved intact, are hand-cut fir, with columns, trim and moldings carved by hand. A small painting is featured in the center of the coffered ceiling. The original shop benches and chests of drawers are set around the reconstructed shop and Bertolla's tools and equipment laid out as they had been originally. Other clockmaker's tools and equipment in the museum's collection are also displayed. Approximately 40 percent of the tools are the original items from Bertolla's shop. Parts of clocks and works in progress are on view on the benches as they were in Bertolla's time. Also preserved in the museum are sketches found in Bertolla's manuscripts, some of which are reproduced on the following pages.

Figure 28.—Detail of wall of Bertolla's workshop, with regulatory clock made by his nephew, Alessandro Bertolla of Venice. Note wheel layouts, etc., scribed in the paneling. (Courtesy of Museo Nazionale della Scienza e della Tecnica, Milan.)

Figure 29.—Table clock by Bertolla in the collection of Doctor Vittorio dal Lago of Bergamo. The dial indicates the days of the week and of the month, the names of the months and lunar phases. The clock strikes the hours and quarters and repeats. (Courtesy of Sig. Luigi Pippa of Milan.)

The shop contains two completed clocks made by Bertolla. One is a weight-driven lantern clock typical of the 18th century, Italian style with brass dial, plates and posts, anchor escapement, and striking work. The dial is engraved in the usual style of Bertolla's baroque design, and the hands are of pierced bronze. Another clock associated with Bertolla and found in the shop, was made by his nephew, Alessandro Bertolla, who worked in Venice after his apprenticeship with his uncle had been completed. This clock is a regulator with a seconds' pendulum and sweep hand on an enameled dial. The original case has not survived.

Figure 30.—Layout of the wheelwork of a clock made by Bertolla for His Excellency Paulo Dona, inscribed "Design No. 1." (Courtesy of Museo Nazionale della Scienza e della Tecnica, Milan.)

Figure 31.—Pendulum arrangement sketch for an unidentified clock found in Bertolla's workshop. (Courtesy of Museo Nazionale della Scienza e della Tecnica, Milan.)

Figure 32.—Striking clock sketch found in Bertolla's manuscripts. (Courtesy of Museo Nazionale della Scienza e della Tecnica, Milan.)

Figure 33.—Fifteen-day striking clock sketch, inscribed "Design No. 3," found in Bertolla's workshop. (Courtesy of Museo Nazionale della Scienza e della Tecnica, Milan.)

Figure 34.—Dial plate of a brass lantern clock made by Bertolla at the age of 80. (Courtesy of Museo Nazionale della Scienza e della Tecnica, Milan.)

Figure 35.—Movement of brass lantern clock produced by Bertolla at the age of 80, showing details of movement and double bell. (Courtesy of Museo Nazionale della Scienza e della Tecnica, Milan.)

One of the most interesting of Bertolla's clocks, and probably the last one which he produced, was found in his workshop. This timepiece indicates the hours, minutes and quarters by means of a single hand or index. The weight-driven clock strikes the hours and quarters on two bells with a single hammer. The chapter ring, which is soldered to the dial plate, is marked for the minutes on the outer rim and for the four quarters inside it. Over the center of it, is a semicircular opening in the dial plate through which is visible a revolving disk attached behind the dial plate. This disk is marked with the hours and revolves from right to left, the current hour being indicated by a projection from the minute ring. The brass dial plate is engraved with simple floral designs in the corners and around the broken arch. There is no comparison between this crude and simple decoration and the extremely fine quality of the engraving on the dial plate of the Borghesi clock, for instance. In the center of the dial plate is engraved the following:

"Questo orologio l'ideai e lo feci nella mia avanzata età d'anni 80. Barto Anto Bertolla"

(I designed and made this clock at my advanced age of 80 years. Bartolomeo Antonio Bertolla.)

Appendix

SYNOPSIS OF THE COMPLETE MECHANICAL WORKS OF THE FIRST CLOCK

[Translated from the section entitled "Synopsis Totius Operis Mechanici" in Francesco Borghesi's first book Novissima Ac Perpetua Astronomica Ephemeris Authomatica Theorico-Practica….]

I

Of three movable indices, the farthest from the center of the dial is fitted with an index on either side and marked with four segments of a circle. Immediately below are five numbers, divided into the days of setting the measure of the mean-synodic age of the moon, and into signs, degrees of the signs, and of the distance of the moon from the sun. These, in each revolution, revolve once around the solar disk superimposed on the mean synodic-lunar disk, and also around the lunar disk. The upper indices, meanwhile, in the two external greatest orbits, measure the time continuously, in the accustomed manner of the Germans—the middle index measuring by hours and the uppermost by the first minutes [of hours].

II

Inside these three circles, perpendicular above their center, is a small index of the seconds of minutes. At each first minute of time, being the fastest of all, it describes the smallest orbit. Next to this are two other slightly larger circles divided into 30 degrees, one [rotating?] from the right, the other from the left. These two indices are arranged in such a fashion that the one rotating from the observer's left completes its period 12 times during one, mean, solar-astronomical year. The one [rotating] from the right likewise completes its cycle 12 times during the period of one mean-synodic moon. In between these, there is placed another small sphere, divided into 40 arbitrary parts, whose dial does not move automatically, but is moved by hand for speeding up or slowing down the course of the time, or of the perpendicular.

III

Diagonally from the sides of the center of the three larger indices, six other indices revolve: three on the left from one center, and three on the right from another. The uppermost of the three which are on the right of the observer [and which are] decorated with a small disk of the sun, runs its cycle once during a mean solar-astronomical year. The second measures the distance of the sun from its apogee. The third revolves 12 times, with each lunar revolution from one node to the same [repeated] node. Under the point of the uppermost index, first lie the months of the year which are inscribed, and the days of each month, but having only 28 days assigned to February; then the signs of the zodiac, and their several degrees. The circle corresponding to the middle index, extending through the first semicircle from apogee to the lower perigee and returning through the second semicircle to the upper locations of apogee, shows the true equation or eccentricity of the sun, joined with the little equation of the moon in syzygy. [These equations are] measured by geometric-astronomic proportion for each distance of the sun from its apogee or perigee in degrees, and in sufficiently small parts of degrees, with the title added above in their proper places, whether an addition is to be made to the mean location of the sun or a subtraction from the same, so that the true longitude of the sun may be calculated. Three circles are assigned to the lowest index, of which 30 degrees of distance of the moon from its nodes comprise the larger. The middle circle is based on the hypothesis of the mean invariable diameters (that is, of the sun, the moon, and the terrestrial shadow), and is divided into hours and quarters of duration. The last circle is divided by the trigonometric laws into the inches of magnitude of lunar eclipses. Lying between these circles, there is another eccentric circle (black with a spot) exhibiting the shadow of the earth, in which the little moon sinks itself, carried by the lowest index. In any ecliptic full moons, the patent number of inches of immersion somehow affects the minds of the cultured, but also the scheme of maximum obscuration affects the eyes of the illiterate themselves.

IV

Of the three indices which revolve from the left, the uppermost completes its cycle within 12 hours, just as the hour index. The middle one with two pointers on diametrically opposite sides, carries the marks of conjunction and opposition of the luminous bodies, with a movement equal to the course of the sun from lunar apogee or perigee. The lowest index, fitted with a single pointer, indicates the motion of the moon from its apogee or perigee. Under these three indices, there is situated a common circle, divided into 12 parts, each of which are further divided into 30 parts through its outer circumference. I have said a common circle, for, with respect to the first index, the division represents 12 hours, and the double subdivision representing the double set of minutes of the hours serves for an excitator for anytime at all, at will. For as often as the little index reaches the twelfth hour, first being moved by hand wherever you prefer, a little hammer strikes the little bell many times. But if you observe the second or the third index, the first division provides the signs, and the subdivision of the signs gives the individual degrees of the distance of the sun from the lunar apogee, or of the moon from its apogee, respectively. To this is added two other interior circles from the same center: to the larger is inserted the equation of the center of the moon in its conjunctions and oppositions; and on the smaller the equation of the same moon in its quarters, astronomically-geometrically proportioned to the distance of the moon from its apogee or perigee. In the first case, the equation is to be subtracted from the mean longitude of the moon, descending from apogee to perigee; in the second case, to be added to the mean longitude of the moon ascending from perigee to apogee; and, in the third semicircle of the index, as the rubric directs, common to both equations, added around the center.

V

Perpendicularly under the center of the machine, two other indices are carried about one and the same center. The one nearer to the observer—bearing in one of two points diametrically opposite the small disk of the sun, in the other the disk of the moon—runs a course equal to the motion of the sun from the head or the tail of the dragon (Draco). The other, of simple construction, marked with a small moon, signifies in like manner the motion of the moon from the head or the tail of the dragon.

Immediately below, there is a larger circle, common [referring] to both these indices, which is divided into 12 parts. Each of these parts in turn, in the outer periphery, is subdivided further into 30 parts, which are the 12 signs of the zodiac and the individual degrees of the signs of distance of the sun and the moon from the head of the dragon.

In the second circle is read the latitude of the moon, measured by degrees, etc., on a trigonometric scale, by signs and degrees of distance of the moon from its nodes, that is, from the head or tail of the dragon. When the second index is descending from the head of the dragon to the tail, the latitude will be to the north of the solar path; that is, the ecliptic. On the other hand, it will be south of the ecliptic when the same index is returning upward from the tail to the head of the dragon as advised by the title inscribed on the third circle.

Finally, on the fourth and last circle are seen more prime minutes of the circle for reducing the orbit of the moon to the ecliptic. That the true longitude of the moon may be obtained more accurately, these must be subtracted from the longitude of the moon already calculated in the first and third quadrant of the circle of the second index. On the other hand, they are to be added to the same in the second and fourth quadrant, as is noted in their respective places, according to the theory of right ascensions.

Here, then, [you have] as finally completed, delineation of the great index which was partially described before in this book.

From two points of that index which perpendicularly correspond to the center of these circles, a pair of compasses, by an unvaried aperture up to the circumference of the first larger circle, has marked off four segments of a circle. The two larger segments, equal among themselves, in one aperture refer to the sun, and the two smaller in the other, likewise equal, refer to the moon. The one pointer is for determining the solar eclipses; the other, for lunar. Both segments of each division, like little wings of the index, stretch to the extent of the degree of distance of the moon from its nodes, and to which that determined latitude corresponds. On one side, that latitude precisely equals the radii of the earth, the sun, and the moon, as the termini of solar eclipses; and, on the other side, precisely equals the radii of the earth's shadow and of the moon, as the confines of lunar eclipses. The apexes of the last index, diametrically limited [opposite], indicate the age of the moon, and its mean distance from the sun; one pointer, upon which the sun sits, measuring the mean days and degrees from the full moon; the other, on which the moon sits, measuring the mean days and degrees from the new moon.

VI

Besides the larger and smaller indices already mentioned, all [of which] revolve within the periphery of the three largest circles, six dials in this clock also revolve within the same circles which are to be seen through six openings of the frontispiece. The first of these, intended to indicate the phases of the moon by an unusual method (completely black, and decorated with the characters of the principal aspects of the moon) continually revolves interiorly around the center of the machine and at the new moon, it completely removes from sight the face of the moon through the round window. It continually recedes through the first half of the circle until, at the time of the full moon, it restores the moon, looking out with a full star. Soon again, too slow to be observed, it returns through the other half of the circle, so that in the next conjunction, the whole face of the moon may have a covering of darkness, once again to be removed.

The other dials are moved by spontaneous advances at stated times. The first of these shows, through a square opening, the day of the month; the second, through another opening, shows the current day of the week with the characters of the seven planets which, according to ancient superstition, preside over each day of the week (now, by a truer form of religion divided by the Church into ferias, etc.); that is, the sun, the moon, Mars, Mercury, Jupiter, Venus and Saturn, to which I have added the numbers of the ferias. These two little dials are advanced daily, by a sudden movement at midnight. The remaining three are changed automatically only once a year on the first of January.

The first of these dials contains five little cells, opening from a common window: in the first cell, at the edge of the dial, is found the dominical letter; in the second, the cycle of the sun; in the third, the character; in the fourth, the sign; and, in the fifth, the house of the planet dominating the year. The second dial shows the epacts, with the golden number. The third, and last of all, shows the Roman cycle.

Finally, as indicated by the epact and the dominical letter in an immovable table added outside, are the feastdays and other movable events of the year; that is, Easter, the four seasons, the Rogation Days, etc.

VII

But lest the various movements of the indices and the various beginnings of the divisions tend to cause some fatigue, the precaution has been taken, that all the indices by common law are moved from the top towards the right of the observer, and from thence all the arithmetic divisions of the circles take their beginning. And lest the multitude of different figures should deceive the eye, the larger divisions of the circles have been marked by Roman numbers, that is, by capital letters of the alphabet; others, in other places, by differently colored numbers. Thus, the movements of the indices, the distribution of the circles and the multitude of numbers not only do not disturb the eyes and the mind, but rather marvelously delight them.

VIII

After having completed briefly the description of the dial and the indices and their motions, I have not without reason delayed in satisfying the desires of many who wish to learn at least the method by which, from this mechanism, may be calculated the true times of new and full moons, and their ecliptics. In order to make these matters clearer, it is necessary that they be explained here at greater length.

With the indices, then, adjusted astronomically-geographically to the longitude of any given region, and to the mean time whether past, present or future, and assuming the clock to be in normal operation (as at present it has been for a whole year and more), then the moon will be in conjunction with the sun in the heavens. When the equations on the mechanism are examined, the sun and moon shall be found to be in the same degree of longitude, and in the same part of a degree. There will also be an ecliptic new moon that is in conjunction with a solar eclipse, or rather with a terrestrial eclipse. This will occur if, at that time, both apexes of the first index, located below the center of the clock, are hidden by the two segments of the circle extending from the center of the mechanism through the lowest index.

And the eclipse will be greater and greater and, consequently, visible in more regions of the earth, the more deeply the two pointers, indicating the distance of the sun from its apogee, are hidden in the center of the segments.

But whether the eclipse takes place in the head or in the tail of the dragon, or whether it is north or south, is indicated by the small disk of the sun attached to one of the two pointers hidden by the segments of the circle. If, at that time, the little disk shall be found in the head of the dragon inscribed on the plane of the dial, then the sun has been snatched from the earth and ingloriously entombed, as it were, in the huge jaw of the dragon. Then, … the heavens themselves will lend aid to the woeful pomp of the senseless funeral in full darkness by suddenly lighting the unhappy lamps of the fixed stars. However, if the little disk occupies the tail of the dragon on the mechanism, then the sun in the heavens also, as if freed from the toils of the immense dragon's tail, will emerge without difficulty.

The center of the eclipse will traverse the hemisphere of the earth north of the solar path, always nearer to the pole of the ecliptic, in proportion to the inclination of the disk to the north. On the other hand, if the little disk inclines to the left semicircle, then the people south of the solar path will enjoy the spectacle of the total central eclipse.

But if the little disk remains neutral (inclining neither way) and remains halfway between the two sections of the circle, then the greatest solar eclipse will take place at the equator and those who live near the poles of the ecliptic will not enjoy a trace of that eclipse. This is because the half of the equatorial diameter enormously outmeasures even the greatest apparent semidiameters of the sun and of the moon, even taking as a norm the smallest horizontal parallax of the moon.

What has been said about the true new moon is to be understood also, proportionately, about the true full moon. For when, with respect to the equations of the centers, the moon shall be distant on the mechanism by a full semicircle from the sun (also in the heavens it will be truly in opposition to the sun) there will be a true full moon. Likewise, the moon in the heavens will be in eclipse if, at the time of opposition, the pointers of the little index (which we mentioned before) situated below the center of the clock are so far away from the belly of the dragon that they are forced to lie under the two smaller segments of the circle which, in all full moons, are always to be moved from the index of the synodic moon to the region of that little index. As a matter of fact, the closer the little pointers approach to the middle of the segments, the more obscured it will be.

You will know, furthermore, that the eclipse of the moon occurs in the head of the dragon if the disk of the little moon, attached to the other point of the little index, is raised to the head of the dragon; conversely, when the little disk of the moon inclines to the tail, the eclipse is taking place in the tail of the dragon.

And, accordingly, when you observe the little moon of the index inclined to one or other section of the circle, so also in the heavens, the eclipse of the moon is only partial and the northern or the southern part of the moon is illuminated.

The current time will indicate whether the lunar eclipse is visible or not. As the new moon ecliptic falls during the day, the eclipse will not be visible, since the earth denies a sight of the moon which is below the horizon. But, conversely, if there are no clouds, the eclipse will be visible anywhere, if the luminous bodies are ecliptically in opposition at night.

Since lunar eclipses appear to all people as being of the same magnitude and duration, and begin and dissipate at the same absolute moment of time, I decided to reveal another facet of this spectacle on the right side of the center of the clock (see chapter III above). There, at the time of the true ecliptic full moon, as the pointer of the third little index shows, you can ascertain the hours, etc., of duration, and the inches of greatest obscuration. The little moon attached to the index is a model of the actual eclipsed moon.

IX

Thus, with the aid of this machine, solar and lunar eclipses of the past can be recalled and future ones can be foreseen. Indeed, if the index of prime minutes is speeded up by hand, whose wheel imparts motion to the other indices and shields, then, the dials and openings will foretell the year, month, day, hour, etc., of any future eclipse. I foresaw that the times would thus be evolved too slowly, and that the clock wheels would be considerably worn by repeated experiments (if, for instance, by the rotation of the index of prime minutes, to whose period only a single hour corresponds, the future new and full moon ecliptics were being investigated). Therefore, I took care that the wheel which immediately communicates motion to the index of the synodic moon should be so fitted internally to the mechanism that by the reversal of any external index, the wheel would be removed from its proper position; whenever desired, it could be quickly and most accurately restored to its proper place.

In this way, since the close meshing of the wheels is released, you can extend the experiment for many years, even for many centuries. You have only to guide with your hand the index of the synodic moon on the circles, always intently observing whether, in the passage which this index makes over the little index, both pointers of the little index are hidden by the segments of the circle. Having observed this, look at the index moved by hand, for if this has carried the solar disk halfway between the two larger segments of the circle to the region of the hidden little index, then you will know that eclipse will be a solar eclipse. On the other hand, you will know that it will be a lunar eclipse, if the index (moved by hand) has carried the moon, situated between the two smaller segments of the circle, to the same region (i.e., the hidden part of the circle). The solar disk and the lunar disk alternately will reveal to you the circumstances of both eclipses. The current year will be given by the Julian period, reducible to any desired epoch, and, contained in the solar cycle, the golden number and the Roman cycle. The month of the year and also the day of the month will be indicated by the pointer of the little index, first on the right side of the clock. And what I have said of future eclipses should be equally understood of past eclipses, so long as the index, which can be moved either way at will, is moved in reverse.

Finally, though 55 wheels were employed to carry so many dials, all are driven by one source of power not exceeding the third part of a Germanic hundred-weight which, suspended at the geometric height of five feet (about the ordinary stature of a man), keeps the whole machine in operation for a hundred days and more.

Although the machine repeats hours and quarter hours at will and, consequently, the number of wheels and the rest of the apparatus necessary for these functions is thereby increased, it has not grown to an unwieldy size, however much one might erroneously imagine it to be. It does not exceed the bulk of ordinary clocks hanging from a wall; indeed, it scarcely equals these.

The entire machine, ready for operation, does not weigh more than 156 ounces, although it is made of steel or brass throughout and further weighted with two bells and a rather large brass dial-plate.

Of course, there are many more things to be said, especially about the mechanical structure of the wheels, but fearing to tire my kind reader unduly by exceeding the bounds of a summary, I am forced to put an end, though unwillingly, to this sufficiently shortened explanation of the work. I have hope of giving satisfaction to many more when I shall have communicated to the learned world another and completely new automatic work, grander than this present one. It is already theoretically completed in all its calculations, but still to be worked out mechanically from the very beginning, if but God, thrice Best and Greatest, bless the undertaking and mercifully grant life and health—to whom be in, and from, and through all things, all honor and glory in eternity and beyond.

BIBLIOGRAPHY

The following works have been used in compiling the material for this paper. They are frequently referred to in the text in shortened form.

Ambrosi, Francesco. Scrittori ed artisti Trentini. Trent: Giovanni Zippel, 1883.

Bonomi, L. Naturalisti, medici e tecnici Trentini. Trent: privately printed, 1930.

Borghesi, Francesco. Novissima ac Perpetua Astronomica Ephemeris Authomatica Theorico-Practica. Trent: Giovanni Battista Monauni, 1763(?).

—— Novissimum Theorico-Practicum Astronomicum Authoma Juxta Pariter Novissimum Mundi Systema. Trent: Giovanni Battista Monauni, 1764.

Engelmann, Max. Philipp Matthäus Hahn. Berlin: Verlag Fischer, 1923.

Esposti, Alfredo degli. La sala 'Innocente Binda' al Museo della Scienza e della Tecnica di Milano. La Clessidra (July 1960), anno 16, no. 7, pp. 18-21.

Franch, Leone. La Valle di Non. Trent, 1953.

Lloyd, H. Alan. Some outstanding clocks over seven hundred years, 1250-1950. London: Leonard Hill, 1958.

Mosna, Ezio. Trento. Trent, 1914.

Perini, Agostino (compilatore). Statistica del Trentino, Biblioteca Communale del Trentino. Vol. 2, p. 57 (cons. 6, carta 9).

Piamonte, Guiseppe. La nauna descritta al viaggiattore. Milan, 1829.

Pippa, Luigi. Antonio Bartolomeo Bertolla. La Clessidra (January 1961), anno 17, no. 1, pp. 22-25.

San Cajetano, David à. Praktische Anleitung für Künstler, alle astronomische Perioden durch brauchbare bisher noch nie gesehene ganz neue Räderwerke mit Leichtigkeit vom Himmel unabweichlich genau auszuführen, sammt Erweiterung der Theorie des neuen Rädergebäudes. Vienna: privately printed, 1793.

Tovazzi, Giangrisostomo. Biblioteca Tirolese. Vol. 2, art. 329, MS. 168, pp. 406-407. Trent, 1780.

Vischer, George F. Beschreibung mechanischer Kunstwerke, welche unter der Direktion und Anweisung M. Philipp Matth. Hahn, Pfarrers in Kornwestheim…. Stuttgart: Mezler, 1774.

Von Bertele, Hans. The development of equation clocks. La Suisse Horologere (1959-1961), parts 1 through 5.

Wenham, Edward. Tall case clocks. The Antiquarian Magazine (May 1927), vol. 8, no. 4, p. 33. [The Borghesi clock is illustrated only from a photograph of the Anderson Art Galleries in New York, and mislabeled "Astronomical Clock made in Jena, 1656, in elaborate mahogany case."]

Footnotes have been moved to the end of the main section of the paper, and illustrations have been moved to eliminate breaks in paragraphs. Minor punctuation errors have been corrected without note. The following typographical errors have been corrected:

p. 41 … Bertolla apparently wavered in … [Had 'waivered'.]
p. 45 … Assidvo proni donant di cvncta labori. [Had 'ronip'.]
Footnote 4: Philipp Matthäus Hahn [Had 'Matthaus'.]

Contributions from
The Museum of History and Technology:
Paper 36

The Engineering Contributions
of Wendel Bollman

Robert M. Vogel

EARLY CAREER 80

THE BOLLMAN TRUSS 85

W. BOLLMAN AND COMPANY 91

FINAL USE OF THE BOLLMAN TRUSS 95

KNOWN BOLLMAN WORKS 99

BIBLIOGRAPHY 104

INDEX

Figure 1.—Wendel Bollman, C.E. (1814-1884). (Photo courtesy of Dr. Stuart Christhilf.)

Robert M. Vogel

THE ENGINEERING CONTRIBUTIONS OF WENDEL BOLLMAN

The development of structural engineering has always been as dependent upon the availability of materials as upon the expansion of theoretical concepts. Perhaps the greatest single step in the history of civil engineering was the introduction of iron as a primary structural material in the 19th century; it quickly released the bridge and the building from the confines of a technology based upon the limited strength of masonry and wood.

Wendel Bollman, self-taught Baltimore civil engineer, was the first to evolve a system of bridging in iron to be consistently used on an American railroad, becoming one of the pioneers who ushered in the modern period of structural engineering.

The Author: Robert M. Vogel is curator of civil engineering in the Smithsonian Institution’s Museum of History and Technology.

Wendel Bollman’s name survives today solely in association with the Bollman truss, and even in this respect is known only to a few older civil and railroad engineers. The Bollman system of trussing, along with those of Whipple and Fink, may be said to have introduced the great age of the metal bridge, and thus, directly, the modern period of civil engineering.

Bollman’s bridge truss, of which the first example was built in 1850, has the very significant distinction of being the first bridging system in the world employing iron in all of its principal structural members that was used consistently on a railroad.

The importance of the transition from wood to iron as a structural and bridge building material is generally recognized, but it may be well to mention certain aspects of this change.

The tradition of masonry bridge construction never attained the great strength in this country which it held in Europe, despite a number of notable exceptions. There were several reasons for this. From the very beginning of colonization, capital was scarce, a condition that prevailed until well into the 19th century and which prohibited the use of masonry because of the extremely high costs of labor and transport. An even more important economic consideration was the rapidity with which it was necessary to extend the construction of railways during their pioneer years. Unlike the early English and European railways, which invariably traversed areas of dense population and industrial activity, and were thus assured of a significant financial return almost from the moment that the first rail was down, the Baltimore and Ohio and its contemporaries were launched upon an entirely different commercial prospect. Their principal business consisted not so much in along-the-line transactions as in haulage between principal terminals separated by great and largely desolate expanses. This meant that income was severely limited until the line was virtually complete from end to end, and it meant that commencement of return upon the initial investment was entirely dependent upon the speed of survey, graduation, tunneling, and bridging.

Figure 2.—Model of B. H. Latrobe’s truss, built in 1838, over the Patapsco River at Elysville (now Daniels), Maryland. (Photo courtesy of Baltimore and Ohio Railroad.)

The need for speed, the general attenuation of capital, and the simple fact that all the early railroads traversed thickly forested areas rendered wood the most logical material for bridge and other construction, both temporary and permanent.

The use of wood as a bridge material did not, of course, originate with the railroads, or, for that matter, in this country. The heavily wooded European countries—Switzerland in particular—had a strong tradition of bridge construction in timber from the Renaissance on, and naturally a certain amount of this technique found its way to the New World with the colonials and immigrants.

America’s highway system was meager until about the time the railroad age itself was beginning. However, by 1812 there were, along the eastern seaboard, a number of fine timber bridges of truly remarkable structural sophistication and workmanship.

It was just previous to the advent of the railroads that the erection of highway bridges in this country began to pass from an art to a science. And an art it had been in the hands of the group of skilled but unschooled master carpenters and masons who built largely from an intuitive sense of proportion, stress, and the general “fitness of things.” It passed into an exact science under the guidance of a small number of men trained at first in the scientific and technical schools of Europe, and, after about 1820, in the few institutions then established in America that offered technical instruction.

The increasing number of trained engineers at first affected highway bridge construction not so much in the materials used but in the way they were assembled. In a bridge designed by a self-taught constructor, the cheapness of wood made it entirely feasible to proportion the members by enlarging them to the point where there could be no question as to their structural adequacy. The trained engineer, on the other hand, could design from the standpoint of determining the entire load and then proportioning each element according to the increment of stress upon it and to the unit capacity of the material.

By the time railroads had started expanding to the West there had been sufficient experience with the half dozen practical timber truss systems by then evolved, that there was little difficulty in translating them into bridges capable of supporting the initial light rail traffic.

In spite of its inherent shortcomings, wood was so adaptable that it met almost perfectly the needs of the railroads during the early decades of their intense expansion, and, in fact, still finds limited use in the Northwest.

Early Career

Wendel Bollman was born in Baltimore of German parents in 1814. His father was a baker, who in the same year had aided in the city’s defense against the British. Wendel’s education, until about the age of 11, was more or less conventionally gained in public and private schools in Baltimore. He then entered into informal apprenticeship, first to an apothecary in Sheperdstown, Virginia (now West Virginia), and then to one in Harpers Ferry. In 1826 or 1827 he became ill and returned to Baltimore for cure. From that time on his education was entirely self-acquired.

Figure 3.—Trussed beam.

It is of interest, in light of his later career, to note that on the Fourth of July 1828, he marched with other boys in a procession that was part of the Baltimore and Ohio Railroad’s cornerstone-laying ceremony. Shortly afterward, he apprenticed himself to a carpenter for a brief time, but when the work slacked off he obtained work with the B. & O. The right-of-way had been graded for about five miles by that time, but no rail was down. The boy was at first given manual work, but soon advanced to rodman and rapidly rose as he gained facility with the surveying apparatus. In the fall of 1829 he participated in laying the first track. As his mother was anxious that he continue his education in carpentry, he left the railroad in the spring of 1830 to again enter apprenticeship. He finished, became a journeyman, helped build a planter’s mansion in Natchez, and returned to Baltimore in 1837 to commence his own carpentry business. The next year, while building a house in Harpers Ferry, he was asked to rejoin the B. & O. to rebuild parts of its large timber bridge over the Potomac there, which had fallen victim to various defects after about a year’s use.

Figure 4.—Simple beam of 50-foot span with three independent trussing systems. Bollman’s use of this method of support led to the development of his bridge truss. This drawing is of a temporary span used after the timber bridge at Harpers Ferry was destroyed during the Civil War. (In Baltimore and Ohio Collection, Museum of History and Technology.)

Shortly after the Harpers Ferry bridge reconstruction, Bollman was made foreman of bridges. It is apparent that, on the basis of his practical ability, enhanced by the theoretical knowledge gained by intense self-study, he eventually came to assist Chief Engineer Benjamin H. Latrobe in bridge design. He later took this work over entirely as Latrobe’s attentions and talents were demanded in the location and extension of the line between Cumberland and Wheeling.

Figure 5.—Bollman’s original patent drawing, 1851. (In National Archives, Washington, D.C.)

The B. & O. did not reach its logical destination, Ohio (actually Wheeling, West Virginia, on the east bank of the Ohio River) until 1853. In the years following Bollman’s return to the railroad, the design of bridges was an occupation of the engineering staff second in importance only to the location of the line itself. During this time Bollman continued to rise and assume greater responsibilities, being appointed master of road by Latrobe in 1848. In this position he was responsible for all railroad property that did not move, principally the right-of-way and its structures, including, of course, bridges.

The recognition of Bollman’s abilities was in the well-established tradition of the B. & O., long known as America’s first “school of engineering,” having sponsored many early experiments in motive power, trackwork, and other fundamental elements of railroad engineering. It furnished the means of expression for such men as Knight, Wright, Whistler, Latrobe, and Winans.

Figure 6.—Plan of Harpers Ferry bridge as built by Latrobe. The second Winchester track was later removed.

Of these pioneer civil and mechanical engineers, some were formally trained but most were self-taught. Bollman’s career on the B. & O. is of particular interest not only because he was perhaps the most successful of the latter class but because he was probably also the last. He may be said to be a true representative of the transitional period between intuitive and exact engineering. Actually, his designing was a composite of the two methods. While making consistent use of mathematical analysis, he was at the same time more or less dependent upon empirical methods. For years, B. & O. employees told stories of his sessions in the tin shop of the railroad’s main repair facility at Mount Clair in Baltimore, where he built models of bridges from scraps of metal and then tested them to destruction to locate weaknesses. It seems most likely, however, that the empirical studies were used solely as checks against the mathematical.

Figure 7.—Recent model of Bollman’s Winchester span. Only two of the three lines of trussing are shown. The model is based on Bollman’s published description and drawings of the structure. (USNM 318171; Smithsonian photo 46941.)

In the period when Bollman began designing—about 1840—there were fewer than ten men in the country designing bridges by scientifically correct analytical methods, Whipple and Roebling the most notable of this group. By 1884, the year of Bollman’s death, the age of intuitive design had been dead for a decade or longer.

Figure 8.—The Baltimore and Ohio Railroad’s Potomac River crossing at Harpers Ferry, about 1860. Bollman’s iron “Winchester span” of 1851 is seen at the right end of Latrobe’s timber structure of 1836, which forms the body of the bridge. (Photo courtesy of Harpers Ferry National Historical Park.)

The B. & O. was in every way a truly pioneer enterprise. It was the first practical railroad in America; the first to use an American locomotive; the first to cross the Alleghenies. The spirit of innovation had been encouraged by the railroad’s directors from the outset. It could hardly have been otherwise in light of the project’s elemental daring.

The first few major bridges beyond the line’s starting point on Pratt Street, in Baltimore, were of rather elaborate masonry, but this may be explained by the projectors’ consciousness of the railroad’s significance and their desire for permanence. However, the aforementioned economic factors shortly made obvious the necessity of departure from this system, and wood was thereafter employed for most long spans on the line as far as Harpers Ferry and beyond. Only the most minor culverts and short spans, and those only in locations near suitable quarries, were built of stone.

In addition to the economic considerations which prompted the company to revert to timber for the major bridges, there were several situations in which masonry construction was unsuitable for practical reasons. If stone arches were used in locations where the grade of the line was a relatively short distance above the surface of the stream to be crossed, a number of short arches would have been necessary to avoid a very flat single arch. In arch construction, the smaller the segment of a circle represented by the arch (that is, the flatter the arch), the greater the stress in the arch ring and the resulting horizontal thrust on the abutments.

Figure 9.—Bollman skew bridge at Elysville (now Daniels), Maryland, built in 1853-1854. (Photo courtesy of Maryland Historical Society.)

The piers for the numerous arches necessary to permit an optimum amount of rise relative to the span would have presented a dangerous restriction to stream flow in time of flood. By the use of timber trusses such crossings could be made in one or two spans with, at the most, one pier in the stream, thus avoiding the problem.

The principal timber bridges as far west as Cumberland were of Latrobe’s design. These were good, solid structures of composite construction, in which a certain amount of cast iron was used in joints and wrought iron for certain tension members. They were, however, more empirical than efficient and, for the most part, not only grossly overdesigned but of decidedly difficult fabrication and construction.

What is interesting about the Latrobian timber trusses, however, is the effect they appear to have had upon Bollman’s subsequent work in the design of his own truss. This effect is evidenced by the marked analogy between the primary structural elements of the two types. The Latrobe truss at Elysville (fig. 2) was only partially a truss, inasmuch as the greater part of the load was not carried from panel to panel, finally to appear at the abutments as a pure vertical reaction, but was carried from each panel (except the four at the center) directly to the bearing points at the piers by heavy diagonal struts, after the fashion of the famous 18th-century Swiss trusses of the Grubenmanns. It was a legitimate structural device, and the simplest means of extending the capacity of a spanning system. However, it was defective in that the struts applied considerable horizontal thrust to the abutments, requiring heavier masonry than would otherwise have been necessary.

It is quite likely that Latrobe did not have absolute confidence in the various pure truss systems already patented by Town, Long, and others, and preferred for such strategic service a structure in which the panel members acted more or less independently of one another. It will be seen that, similarly, the individual panel loads in Bollman’s truss were carried to the ends of the frame by members acting independently of one another.

The Bollman Truss

There had never been any question about the many serious inadequacies of wood as a bridge material. Decay and fire risk, always present, were the principal ones, involving continuous expenditure for replacement of defective members and for fire watches. It was, in fact, understood by the management and engineering staff of the B. & O. that their timber bridge superstructures, though considered the finest in the country, were more or less expedient and were eventually to be replaced. In this regard it is not surprising that Latrobe, a man of considerable foresight, had, at an early date, given serious thought to the possible application of iron here.

Figure 10.—Potomac River crossing of the Baltimore and Ohio at North Branch, Maryland, built in 1856. There are three Bollman deck trusses. (Photo courtesy of Baltimore and Ohio Railroad.)

Figure 11.—The Fink truss. (Smithsonian photo 41436.)

Figure 12.—Advertisement in the Railroad Advocate, August 1855. Click here to read transcription.

The world’s first major iron bridge, the famed cast-iron arch at Coalbrookdale, England, had been constructed in 1779. Its erection was followed by rather sporadic interest in this use of the material. The first significant use of iron in this country was in a series of small trussed highway arches erected by Squire Whipple over the Erie Canal in the early 1840’s, over 60 years later. In these, as in most of the earlier iron structures, an arch of cast iron was the primary support. The thrust of the arches was counteracted by open wrought-iron links with other wrought- and cast-iron members contributing to the truss action.

The Whipple bridges promoted a certain amount of interest in the material. In the B. & O.’s annual report for the fiscal year 1849 appears the first record of Latrobe’s interest in this important matter. In the president’s message is found the following, rather offhand, statement:

$6,183.19 have been expended toward the renewal of the Stone Bridges on the Washington Branch, carried off by the flood of Oct. 7th, 1847. Preparations are made and contracts entered into, for the reconstruction of the large Bridges at Little Patuxent and at Bladensburg which will be executed in a few months…. It is proposed to erect a superstructure of Iron upon stone abutments, at each place—with increased span, for greater security against future floods.

It is interesting to note that it was indeed Bollman trusses to which the president of the railroad had referred. How much earlier than this date Bollman had evolved his peculiar trussing system is not clear. The certain influence of Latrobe’s radiating strut system of trussing has been mentioned. As likely an influence was another basic technique commonly used to increase the capacity of a simple timber beam—that of trussing—i.e., placing beneath the beam a rod of iron that was anchored at the ends of the beam and held a certain distance below it at the center by a vertical strut or post. This combination thus became a truss in that the timber portion was no longer subject to a bending stress but to a simple one of compression, the rod absorbing the tensile stress of the combination. The effect was to deepen the beam, increasing the distance between its extreme fibers and—by thus reducing the bending moment—reducing the stress in them (see fig. 3).

Figure 13.—The four Bollman spans at Harpers Ferry that survived the Civil War. The spans were completed in 1862-1863. (Photo courtesy of Baltimore and Ohio Railroad.)

It apparently occurred to Bollman that by extending the number of rods in a longitudinal direction, this effect could be practically amplified to such an extent as to be capable of spanning considerable distances. He almost certainly did not at first contemplate an all-iron system, but rather a composite one such as described. It is entirely likely that such trussed beams, with multiple systems of tension rods, were used by Bollman as bridging in temporary trestlework along the line as early as 1845 (see fig. 4).

It is impossible to say whether Bollman himself, or Latrobe, was struck with the logic of further elaborating upon the system and, simultaneously, translating the timber compression member into one of cast iron. Cast iron would naturally have been selected for a member that resisted a compressive stress, as it was considerably cheaper than wrought iron. But more important, at that time wrought iron was not available in shapes of sufficient sectional area to resist the appreciable buckling stresses induced in long compression members. The cost of building up members to sufficient size from the very limited selection of small shapes then rolled would have been prohibitive.

The trussing rods, subjected to tension, were of wrought iron inasmuch as the sectional area had only to be sufficient to resist the primary axial stress.

The first all-iron Bollman truss was constructed over the Little Patuxent River at Savage Factory, near Laurel, Maryland, in 1850. In the chief engineer’s report for the year 1850, Latrobe was able to state that the truss had been completed and was giving “much satisfaction.” He went on at some length to praise the “valuable mechanical features” embodied therein, and expressed great confidence that iron would become as important a material in the field of civil engineering as it was in mechanical engineering.

Figure 14.—The Harpers Ferry bridge as completed after the Civil War. It was used by the Baltimore and Ohio until 1894, and as a highway bridge until 1936. (Photo 690, Baltimore and Ohio Collection, Museum of History and Technology.)

The cost of this first major Bollman bridge was $23,825.00. Its span was 76 feet. Latrobe’s confidence was well placed. The Savage span and another at Bladensburg may be considered successful pilot models, for, in spite of a certain undercurrent of mistrust of iron bridges within the engineering profession—due mainly to a number of failures of improperly designed spans—Latrobe felt there was sufficient justification for the unqualified adoption of iron in all subsequent major bridge structures on the B. & O.

Almost immediately following completion of the Savage Bridge, Bollman undertook the design of replacements for the large Patapsco River span at Elysville (now Daniels), Maryland, and the so-called Winchester span of the B. & O.’s largest and most important bridge, that over the Potomac at Harpers Ferry. Harpers Ferry bridge, a timber structure, had been designed by Latrobe and built in 1836-1837 by the noted bridge constructor Lewis Wernwag. It was peculiar in having a turnout, near the Virginia shore, whereby a subsidiary road branched off to Winchester (see fig. 6). Only the single span on this line, situated between the midriver switch and the shore, was slated for replacement, as the other seven spans of the bridge had been virtually reconstructed in the decade or so of their history and were in sound condition at the time.

The Winchester span (fig. 8), which was the first Bollman truss to embody sufficient refinement of detail to be considered a prototype, was completed in 1851. Bollman was extremely proud of the work, with perfect justification it may be said. The 124-foot span was fabricated in the railroad’s extensive Mount Clair shops. It was subdivided into eight panels by seven struts and seven pairs of truss rods. An interesting difference between this span and Bollman’s succeeding bridges was his use of granite rather than cast iron for the towers. The span consisted of three parallel lines of trussing to accommodate a common road in addition to the single-track Winchester line.

The distinctive feature of the Bollman system was the previously mentioned series of diagonal truss links in combination with a cast-iron compression chord, which Bollman called the “stretcher.” The spacing between the chord and the junction of each pair of links was maintained by a vertical post or strut, also cast.

Figure 15.—North Street (now Guilford Avenue) bridge, Baltimore. In this transitional composite structure cast iron was used only in the relatively short sections of the upper chord. For the long unsupported compression members of the web system, standard wrought-iron angles and channels were built up into a large section. The decorative cast-iron end posts were non-structural. (Photo in the L. N. Edwards Collection, Museum of History and Technology.)

Much of the appeal of this design lay unquestionably in the sense of security derived from the fact that each of the systems acted independently to carry its load to the abutments. The lower chords, actually nonfunctional in the primary structure, were included merely to preserve the proper longitudinal spacing between the lower ends of the struts. A certain lack of rigidity was inherent in the system due to that very discontinuity which characterized its action; however, this was compensated for by a pair of light diagonal stay rods crossing each panel. These rods served the additional function of distributing concentrated loads to adjacent struts much in the manner of the bridging between floor joists in a building.

In the Winchester span the floor system was of timber for reasons of economy. This was a very minor weakness inasmuch as any stick could be quickly replaced, and without disturbing the function of the structure. Bollman received a patent for his truss in January 1852, and in the same year published a booklet describing his system in general and the Harpers Ferry span in particular. Here, he first calls it a “suspension and trussed bridge,” which is indeed an accurate designation for a system which is not strictly a truss because it has no active lower chord. (The analogy to a suspension bridge is quite clear, each pair of primary rods being comparable to a suspension cable.) Thereafter, Bollman’s invention was generally termed a suspension truss.

INFLUENCE OF THE TRUSS

Bollman’s 1852 publication was widely disseminated here and abroad and studied with respectful interest by the engineering profession. Its drawings of the structure were copied in a number of leading technical journals in England and Germany. Although there is no record that the type was ever reproduced in Europe, there can be little doubt that this successful structural use of iron by the most eminent railroad in the United States and its endorsement by an engineer of Latrobe’s status gave great impetus to the general adoption of the material. This influence was certainly equal to that of Stephenson’s tubular iron bridge of 1850 over the Menai Strait, or Roebling’s iron-wire suspension bridge of 1855 over Niagara gorge. The Bollman design had perhaps even greater influence, as the B. & O. immediately launched the system with great energy and in great numbers to replace its timber spans; on the other hand, Roebling’s structure was never duplicated in railroad service, and Stephenson’s only once.

Figure 16.—Left: conjectural section of Bollman’s segmental wrought-iron column, about 1860, and section of the standard Phoenix column; right: Phoenix column as used in truss-bridge compression members.

EVALUATION OF THE TRUSS

By the late 1850’s iron was well established as a bridge material throughout the world. Once the previous fears of iron had been stilled and the attention of engineers was directed to the interpretation of existing and new spanning methods into metal, the Bollman truss began to suffer somewhat from the comparison. Although its components were simple to fabricate and its analysis and design were straightforward, it was less economical of material than the more conventional panel trusses such as the Pratt and Whipple types. Additionally, there was the requisite amount of secondary metal in lower chords and braces necessary for stability and rigidity.

A factor difficult to assess is Bollman’s handling of his patent, which was renewed in 1866. There is sufficient evidence to conclude that he considered the patent valuable because it was based upon a sound design. Therefore, he probably established a high license fee which, with the truss’s other shortcomings, was sufficient to discourage its use by other railroads. As patron, the B. & O. had naturally had full rights to its use.

An additional defect, acknowledged even by Bollman, arose because of the unequal length of the links in each group except the center one. This caused an unevenness in the thermal expansion and contraction of the framework, with the result that the bridges were difficult to keep in adjustment. This had the practical effect of virtually limiting the system to intermediate span lengths, up to about 150 feet. For longer spans the B. & O. employed the truss of another of Latrobe’s assistants, German-born and technically trained Albert Fink.

The Fink truss was evolved contemporaneously with Bollman’s and was structurally quite similar, being a suspension truss with no lower chord. The principal difference was the symmetry of Fink’s plan, which was achieved by carrying the individual panel loads from the panel points to increasingly longer panel units before having them appear at the end bearings. This eliminated the weakness of unequal strains. The design was basically a more rational one, and it came to be widely used in spans of up to 250 feet, generally as a deck-type truss (see fig. 11).

W. Bollman and Company

Bollman resigned from the Baltimore and Ohio in 1858 to form, with John H. Tegmeyer and John Clark, two of his former B. & O. assistants, a bridge-building firm in Baltimore known as W. Bollman and Company. This was apparently the first organization in the United States to design, fabricate, and erect iron bridges and structures, pioneering in what 25 years later had become an immense industry. The firm had its foundation at least as early as 1855 when advertisements to supply designs and estimates for Bollman bridges appeared over Tegmeyer’s name in several railroad journals (see fig. 12).

Bollman’s separation from the B. & O. was not a complete one. The railroad continued its program of replacing timber bridges with Bollman trusses, and contracted with W. Bollman and Company for design and a certain amount of fabrication. There is some likelihood that eventually fabrication was entirely discontinued at Mount Clair, and all parts subsequently purchased from Bollman.

The firm prospered, erecting a number of major railroad bridges in Mexico, Cuba, and Chile. Operations ceased from 1861 to 1863 because of difficult wartime conditions in the border city of Baltimore. Following this, Bollman reentered business as sole proprietor of the Patapsco Bridge and Iron Works.

Figure 17.—Chicago, Burlington and Quincy Railroad bridge over Quincy Bay (branch of the Mississippi River) at Quincy, Illinois. The pivot draw-span was formed of two Bollman deck trusses supported at their outer ends by hog chains. The bridge was built in 1867-1868 by the Detroit Bridge and Iron Co., Bollman licensee. (Clarke, Account of the Iron Railway Bridge … at Quincy, Illinois.)

The most noteworthy of Bollman’s works in this period was a series of spans at Harpers Ferry. The B. & O.’s timber bridge had been destroyed by Confederate forces in June 1861, and the crossing was thereafter made upon temporary trestlework. This was a constant source of trouble, with continuing interruptions of the connection from high water, washouts, and military actions. The annoyance and expense of this became so great that the company decided to risk an iron bridge at the crossing. In July and August 1862, two sections of Bollman truss, spans no. 4 and no. 5 were completed. As this occurred during the time when W. Bollman and Company was inoperative, the work was produced at Mount Clair to Bollman’s design and, undoubtedly, erected under his supervision. Five weeks later, on September 24, these and Bollman’s famous Winchester span of 1851 were blown up by the Confederates, and the line’s business was again placed at the mercy of trestling.

The spirit of the B. & O. administration indeed seems to have been unshakable when, in the face of such heartbreaking setbacks, it determined to again bridge the river with iron, even at the height of the hostilities. In November, span no. 5 was erected, and by April 1863 nos. 3, 4, and 6 also. These were the four straight spans in midriver between the “wide” (or “branch,” or “wye”) span and the span on the Maryland shore over the Chesapeake and Ohio Canal (see fig. 13). Although the wood floor system of these spans was burned for strategic reasons by U.S. troops later in 1863, they survived the war.

In 1868 the remaining trestlework was replaced with Bollman trusses. This magnificent structure served the railroad until 1894 when the right-of-way was realigned at Harpers Ferry. However, the half used by the common road remained in use until carried away by the disastrous flood in 1936. The piers may still be seen.

During the prewar years, Bollman evolved a structural development of most profound importance, which is usually associated with the Phoenix Iron Works and its founder, Samuel J. Reeves. In the erection of a high trestlework viaduct for the Havana Railroad, Bollman apparently became concerned with the tensile weakness of cast iron when applied in long, unsupported columns. Although a column is normally subjected to compressive stresses, when the slenderness ratio—that is, the length divided by the radius of gyration of the cross section—becomes great, a secondary bending stress may be produced. If this stress becomes great enough, the value of the tensile stress in one side of the column may actually exceed the principal compressive stress, and a net effect of tension result.

Figure 18.—Ohio River crossing of the Baltimore and Ohio at Benwood, West Virginia, completed in 1870. Bollman deck trusses were used in the approaches on both sides. (Photo 693, Baltimore and Ohio Collection, Museum of History and Technology.)

Figure 19.—Patapsco River crossing of the Baltimore and Ohio between Thistle and Ilchester, Maryland. (Photo 695, Baltimore and Ohio Collection, Museum of History and Technology.)

As already mentioned, the few available rolled-iron shapes were of relatively small area and quite unsuitable for use as columns unless combined and built up in complex fabrications. The normal practice at the time was to use cast compression members in iron bridges and structures, with their sectional area so proportioned to the length that a state of tension could not exist. In the case of long members, this naturally meant that an excessive amount of material was used.

Figure 20.—Two views of Bollman-built “water-pipe truss” that carries Lombard Street over Jones Falls in Baltimore. Built in 1877.

Bollman was conscious of the problem from his experience with the stretchers and struts of his truss, and he must have been aware of the great advantage which would be obtained by a practical method of forming such members in wrought iron, the tensile resistance of which is equivalent to the compressive. He eventually developed the forerunner of what came to be known as the Phoenix form by having special segmental wrought-iron shapes rolled by Morris, Tasker and Company of Philadelphia, these shapes being combined into a circular section with out standing flanges for riveting together. The circular section is theoretically the most efficient to bear compressive loading. A column of any required diameter could be produced by simply increasing the number of segments, the individual size of which never exceeded contemporary rolling mill capacity (see fig. 16).

The design exhibits the inspired combination of functional perfection and simplicity that seems to characterize most great inventions.

Figure 21.—The Harpers Ferry bridge toward the end of its career, carrying a common road over the Potomac. The westernmost line of trussing and span no. 1 had been removed long before. View through the Winchester span looking toward Maryland in 1933. (Photo courtesy of Harpers Ferry National Historical Park.)

It may have been because he had no facilities for rolling that Bollman communicated his idea to Reeves, although this seems illogical. At any rate, Reeves and his associates patented the system extensively, and the Phoenix column was eventually employed to the virtual exclusion of cast-iron and other types of wrought-iron columns. By the end of the 19th century it began to pass from use, as mills became capable of producing larger sections with properties relatively favorable to column use and more adaptable to connection with other members.

Final Use of the Bollman Truss

The Bollman truss found occasional use elsewhere than on the B. & O. lines, but generally only when erected on contract by Patapsco Bridge and Iron Works. However, the fact that Bollman could profitably erect this bridge in the severely competitive 1870’s indicates that the harsh criticism of the system by authorities of such stature as Whipple was not necessarily justified. Bollman’s advertisements, in fact, refer to the favorable recommendations of other such renowned engineers as Herman Haupt and M. C. Meigs.

Figure 22.—Bollman deck trusses in the North River Bridge built in 1873 at Mount Crawford, Virginia, on the Valley Railroad of Virginia (B. & O.). Each end span is 98 ft. 6 in.; the river span is 148 ft. 9 in. (Photo 756, Baltimore and Ohio Collection, Museum of History and Technology.)

An interesting application of the system was in a drawbridge, formed of two Bollman deck spans, over an arm of the Mississippi at Quincy, Illinois (see fig. 17). The first iron bridge in Mexico was erected by Bollman over the Medellín River about 1864. Another work of this period, which attracted considerable attention, was a pair of bridges that Bollman erected over North Carolina’s Cape Fear River in 1867-1868. These bridges were notable for their foundation on cast-iron cylinders, sunk pneumatically. This was one of the first instances of the use of the process in America, and the depth of 80 feet below the water surface reached by one cylinder was considered remarkable for years afterward.

In the last active decade or so of his career, Bollman produced hundreds of minor bridges and other structures. In 1873 he supplied the castings for the splendid iron dome of Baltimore’s City Hall and erected the ingenious water-main truss which carries Lombard Street over Jones Falls in that city. In this structure the top and bottom chords of the central line of trussing are cast-iron water mains, bifurcated at the abutments, and joined by cast- and wrought-iron web members (see fig. 20).

In the mid 1870’s Bollman saw his truss pass into obsolescence. This was due primarily to the generally increasing distrust of cast iron for major structural members due to its brittleness, but advances in structural theory, availability of a greater variety of rolled structural shapes, and the increasing loading patterns of the period all contributed.

Figure 23.—The only surviving Bollman truss bridge, at Savage, Maryland. The bridge was built elsewhere in 1852 and was moved to this now-abandoned Baltimore and Ohio industrial siding in about 1888.

Although no Bollman trusses were built by Bollman or the B. & O. after 1875, those in use were only removed as required by heavier motive power. The Harpers Ferry span, as noted, remained in full main-line service until 1894. Bollman trusses on feeder lines were continued in use until much later; a number of them on the Valley Railroad of Virginia (see fig. 22) were not removed until 1923. However, only on the most isolated spurs was the Bollman truss permitted to reach really ripe age. The sole known remaining example (fig. 23) stands on such a branch—ironically, at Savage, over the Little Patuxent, the site of the first Bollman span. This is not the 1850 bridge, but one built in 1852 and moved to the present site 30 years later. The fate of the first span is not known.

Figure 24.—Hot-water and chocolate pitchers of the 10-piece, silver tea service presented to Bollman by his fellow employees when he resigned from the Baltimore and Ohio in 1858. A railroad motif was used throughout, each piece being circled at top and bottom by a track, complete with rail of accurate section and ties. Spouts are in simulation of hexagonal sheet-iron chimneys, with seams riveted, and the handles are in the form of a surveyor’s telescope. On the various pieces are engraved the designs of the more important B. & O. bridges. Throughout is a wonderful profusion of bits and objects of railroadiana in low relief, high relief, and fully modeled. In Board of Directors Room, Baltimore and Ohio Railroad Company, Baltimore, Md. (Photo courtesy of Baltimore and Ohio Railroad.)

Known Bollman Works

(All B. & O. works listed were designed by Bollman and built by the railroad, unless otherwise indicated.)

Dates of service Location Type No. spans / length of each Remarks

1850-? Savage, Md., Little Patuxent River Bollman through truss /76' First Bollman truss erected; granite towers; cost, $23,825. B. & O. RR.

1851-? Bladensburg, Md., Anacostia River Bollman through truss 1/? Second Bollman truss erected; granite towers; cost, $19,430. B. & O. RR.

1851-1862 Harpers Ferry, Va., Potomac River Bollman through truss /124' Winchester span; first major Bollman truss; three lines of truss; granite towers; blown up by Confederate Army on September 24, 1862. B. & O. RR.

1851-? Baltimore, Md., Carey Street Trestle — Wood trestle bents with wrought-iron diagonals. First use of iron structural members in trestlework. Total length 76 feet. B. & O. RR.

1852- Savage, Md., Little Patuxent River Bollman through truss 2/?80' Still standing. Moved to Savage in 1888; original location unknown. This and succeeding Bollman trusses use iron towers. B. & O. RR.

1852 (or 1853)-? Marriottsville, Md., Patapsco River Bollman truss /50' One of first Bollman trusses with iron towers. B. & O. RR.

1853-? Zanesville, Ohio, Muskingum River Bollman truss /124' (or /160') Double track, Central Ohio RR. Designed by Bollman; built by Douglas, Smith & Co., Zanesville.

1854-1870(?) Elysville (now Daniels), Md., Patapsco River Bollman through truss /97'9" Upper bridge, skew. Cost, $24,477.59. B. & O. RR.

1854-1862 Monocacy, Md., Monocacy River Bollman truss /119' Blown up September 8, 1862; rebuilt in 1864. Cost, $22,722.59. B. & O. RR.

1854-? Eastern Ohio Bollman truss(?) /40' C. O. RR. Section 76 adjacent to 300-ft. tunnel.

1855-? Bridgeville, Ohio, Salt Creek Bollman deck truss /71' C. O. RR.

Pre-1855-? Buffalo, N.Y. — — Unidentified. Mentioned by George Vose in Railroad Advocate (June 9, 1855).

1856-? Elysville, Md., about 1/4 miles east of 1854 bridge, Patapsco River Bollman through truss /111' Lower Bridge. B. & O. RR.

Pre-1856-? Marriottsville, Md. Bollman truss(?) /48'9" Referred to as “Tunnel Bridge” in B. & O. RR. annual report, 1856.

1856-? Near Ijamsville, Md., Bush Creek Iron girders /23'9" Possibly trussed beams; mentioned in B. & O. RR. annual report, 1856.

1856-? Near Ijamsville, Md., Bush Creek Iron girders /23'9" As above.

1856-c.1862 North Branch, Md., Potomac River Bollman deck truss /142' Partially destroyed in Civil War. B. & O. RR.

1860-1906 Chile, Angostura River Bollman truss(?) /115' Chilean Railways. Designed and built by Bollman. Replaced by bridge built by French firm of Schneider, Cruesot & Co.

1860-1910 Chile, Paine River Bollman truss(?) 1/? As above.

Post-1860-? Ilchester, Md., Patapsco River Bollman through truss 1/? B. & O. RR.

Pre-1861-? Cuba Bridges and station house — All bridges on Havana RR., including iron station house and bridge at Guines. Designed and built by Bollman.

Pre-1861-? Cuba Bridges — All bridges on Cienfuegos RR., Cárdenas RR., and Havana & Matanzas RR. Designed and built by Bollman.

Pre-1861-? Cuba Trestle — Trestle with wrought-iron columns (the first such ever constructed). Havana RR. Designed and built by Bollman.

1862-1862 Harpers Ferry, Va., Potomac River Bollman through truss /160' Span no. 3 (July 24) and span no. 4 (August 21). Blown up September 24, 1862. B. & O. RR.

1862-1936 Harpers Ferry, Va., Potomac River Bollman through truss /160' Span no. 5 (November). B. & O. RR.

1863-1936 Harpers Ferry, Va., Potomac River Bollman through truss /160' Spans nos. 3, 4, and 5. Constructed previous to April 1863. B. & O. RR.

1863-? Berwyn, Md., Paint Branch Bollman truss(?) ? Iron bridge mentioned in B. & O. RR. annual report, 1863

1863(4?)-? Clinton, Iowa, Mississippi River Pivot draw /360' Built by Detroit Bridge & Iron Works. It was the longest in the world at time of completion. Designed by Bollman.

1864-? Laurel, Md., Patuxent River Bollman truss ? Replaced stone arch that had been washed out. B. & O. RR.

c. 1864-? Near Veracruz, Mexico, Medellín River Bollman hrough truss /115' Veracruz & Jucaro RR. First iron bridge in Mexico. Designed and built by Bollman.

1864-? Near Point of Rocks, Md., Back Creek Bollman truss(?) /80'(?) Iron bridge mentioned in B. & O. RR. annual report, 1864. The span length given is that of previous stone arch.

1864-? Bladensburg, Md., Anacostia River Bollman truss 1/? Span for second track, to match 1851 span. B. & O. RR.

1868-? Cape Fear, N.C., Northeast Branch, Cape Fear River Bollman truss(?) /146'6" /164' pivot draw/150' Wilmington Railway Bridge Co. This bridge was connected to that over the Northwest Branch by 2/2 miles of timber trestling. Designed and built by Bollman.

1868-? Cape Fear, N.C., Northwest Branch, Cape Fear River Bollman truss(?) /217'(?) pivot draw/150' See above.

1868-? Quincy, Ill., Quincy Bay (in Mississippi River) Bollman deck truss /85' pivot draw/190' Chicago, Burlington & Quincy RR. The pivot draw was formed of two 85-ft. simple Bollman deck spans whose outer ends hung from hog chains. Designed by Bollman; built by Detroit Bridge & Iron Works.

1869-c.1892 Baltimore, Md., over Jones Falls, B. & O. RR., and Northern Central RR. Warren truss /100'
/55'6" North Avenue Bridge. Composite double intersection truss; timber top chord and posts, wrought-iron lower chord and ties. In 55-ft. spans, both chords timber. Cost, $73,588. Built by Bollman.

c.1869-1936 Harpers Ferry, Va., Potomac River Bollman through truss 4/? Canal span (no. 8), Wide span (no. 2), Winchester span, and West End span. Destroyed by flood in 1936. B. & O. RR.

1870-.1895 Baltimore, Md., Jones Falls Iron “Isometrical truss” (probably Pratt type) /108' Charles Street Bridge. Three lines of trussing.Cost, $20,297. Built by Bollman.

1870-1893 & 1900 Bellaire, Ohio-Benwood W. Va., Ohio River Bollman deck truss /107'-125' In approaches; 2 spans on Ohio side; 7 on West Virginia side. B. & O. RR.

1870-c.1895 Belpre, Ohio-Parkersburg, W. Va., Ohio River Bollman deck truss 16/? In approaches; 7 spans on Ohio side; 9 on West Virginia side. B. & O. RR.

1870-? Elysville, Md., Patapsco River Bollman through truss 4/? Skew; replacement of Upper Bridge(?). B. & O. RR.

1871-c.1895 Baltimore, Md., Jones Falls Timber and iron truss ? Decker Street (now Maryland Avenue) Bridge. Cost, $24,975. Built by Bollman.

1871-c.1892 Baltimore, Md., over Northern Central RR. at Jones Falls Warren truss /100' North Avenue Bridge. Composite double intersection truss; cast-iron top chord and posts; wrought-iron bottom chord and ties. West span. Built by Bollman.

1873-1923 Cave Station, Va., Middle River Bollman deck truss /98'7"
/63'5" Valley Railroad of Virginia (B. & O.) Bridge no. 120. The main span was a Whipple deck truss. Replaced with plate girders. Designed by Bollman.

1873-1923 Mount Crawford, Va., North River Bollman deck truss /98'6"
/148'9" Valley Railroad of Virginia (B. & O.) Bridge no. 117. Designed by Bollman.

1873-1923 Verona, Va., North River Bollman deck truss /98'7" Valley Railroad of Virginia (B. & O.) Bridge no. 129. The main span was a 147-ft. Whipple deck truss. Designed by Bollman.

1873-? Wadesville, Va., Opequon Creek Bollman through truss /147'8" Span length given is that of previous wood span that burned in 1862. B. & O. RR.

c. 1873- Baltimore, Md. Iron roof trusses ? First Presbyterian Church. Built by Bollman; possibly designed by him.

1873- Baltimore, Md. Cast-iron stairs City Hall. Cost, $12,840. Designed by George A. Frederick, architect; built by Bollman.

1873- Baltimore, Md. Cast-iron framework Dome of the City Hall. Cost, $70,525. Designed by George A. Frederick; built by Bollman.

1875-c.1913 Baltimore, Md., Jones Falls Iron truss 1/? Fayette Street Bridge. Cost, $9,396. Built by Bollman.

1876-c.1913 Baltimore, Md., Jones Falls Single-beam iron bridge (truss?) 1/? Canton Avenue (now Fleet Street) Bridge. Cost, $8,904. Built by Bollman.

1876-c.1913 Baltimore, Md., Jones Falls Single-beam iron bridge (truss?) 1/? Eastern Avenue Bridge. Cost, $12,382. Built by Bollman.

1877- Baltimore, Md., Jones Falls Pratt and bowstring truss /88'6" Lombard Street Bridge. Three lines of truss; two outer trusses, composite cast- and wrought-iron polygonal Pratt type; center composite bowstring with Pratt-system web. Both chords are cast-iron water mains, bifurcated at the end bearings; cast-iron posts and wrought-iron ties. In service. Cost, $7,632. Designed by Jas. Curran, Baltimore water department; built by Bollman.

1877-c.1913 Baltimore, Md., Jones Falls Iron truss 1/? Bath Street Bridge. Cost, $4,172. Built by Bollman.

1879-? Baltimore, Md. Drawbridge 1/? Over entrance to City Dock. Cost, $13,182. Built by Bollman.

1879-c.1930 Baltimore, Md., over Jones Falls and railroad tracks Warren truss /173'9" North Street (now Guilford Avenue) Bridge. Composite trusses; cast-iron top chord and end posts; wrought-iron bottom chord and web members. Cost, $38,772.45. Built by Bollman; designed by Latrobe.

1881-1960 Baltimore, Md., (Woodberry), Jones Falls Wrought-iron Pratt truss 1/? Union Avenue Bridge. Built by Bollman; possibly designed by him.

?-? Harpers Ferry, Va., Arsenal Canal Bollman through truss /148' Arsenal Branch, B. & O. RR. Skew type. Span length is that of previous timber span.

?-? Baltimore, Md., Gwynns Falls Bollman through truss 2/? B. & O. RR.

BIBLIOGRAPHY

A history and description of the Baltimore and Ohio Railroad by a citizen of Baltimore. Baltimore, 1853.

Baltimore and Ohio Railroad Company. A list of the officers and employees of the Baltimore and Ohio Railroad for November, 1857. Baltimore, 1857.

——. Third annual report of the president and directors to the stockholders of the Baltimore and Ohio Rail Road Company. Baltimore: 1829. (Also the fourth through 38th annual reports. Baltimore, 1830-1864.)

——. Baltimore and Ohio exhibits at the Century of Progress. Chicago, 1934.

Biographical cyclopedia of representative men of Maryland and the District of Columbia. Baltimore, 1879.

Bollman, Wendel. Iron suspension and trussed bridge as constructed for the Baltimore and Ohio Rail Road Co. at Harper’s Ferry, and on the Washington branch of this road. Baltimore, 1852.

——. Letter to John W. Garrett dated June 17, 1862. In files of Division of Mechanical and Civil Engineering, United States National Museum, Washington, D.C.

——. Report of Mr. Bollman in relation to Central Ohio Rail Road. Baltimore, 1854.

Bryant, William C. Picturesque America. New York, 1874.

Clarke, Thomas Curtis. An account of the iron railway bridge across the Mississippi River at Quincy, Illinois. New York, 1869.

Colburn, Zerah. American iron bridges. Minutes of the proceedings of the Institution of Mechanical Engineers (1863), vol. 22, pp. 540-573.

Condit, Carl. American building art:—The nineteenth century. New York: Oxford Press, 1960.

Gray, George E. Notes on early practice in bridge building. Transactions of the American Society of Civil Engineers (1897), vol. 37, pp. 2-16.

Greiner, John E. The American railroad viaduct—Its origin and evolution. Transactions of the American Society of Civil Engineers (1891), vol. 25, pp. 349-372.

Lang, Philip George. Bollman trusses on Valley of Virginia Branch will soon be memories. Baltimore and Ohio Magazine (October 1923), pp. 18-19.

——. The old Baltimore and Ohio bridge crossing the Potomac River at Harpers Ferry, West [sic] Virginia. Engineering News-Record (September 17, 1931), p. 446.

Malezieux, Emile. Travaux publics des Etats-Unis d’Amerique en 1870. Paris, 1873.

McDowell, W. H. Unpublished engineer’s report to the president and directors of Wilmington Railway Bridge Company, Wilmington, North Carolina, dated March 12, 1868. Typewritten copy in files of Division of Mechanical and Civil Engineering, U.S. National Museum, Washington, D.C.

Smith, Charles Shaler. Comparative analysis of the Fink, Murphy, Bollman and triangular trusses. Baltimore, 1865.

Smith, William P. The book of the great railway celebrations of 1857. Baltimore, 1858.

Tyrrell, Henry G. History of bridge engineering. Chicago, 1911.

Whipple, Squire. Bridge building. Albany, New York, 1869.

Transcription of Figure 12 for screen readers.

WENDEL BOLLMAN’S

Patent Iron Suspension Railroad Bridge.

The undersigned would inform the officers of Railroads and others, that he is prepared to furnish Drawings and Estimates for Bridges, Roofs, etc., on the plan of Bollman’s Patent.

The performance of these bridges, some of which have been in use for six years, has given entire satisfaction. Their simplicity of construction renders repairs easy and cheap, and by a peculiar connection of the Main and Panel Rods at the bottom of the Posts, all danger from the effects of expansion, which has heretofore been the chief objection to Iron Bridges, is entirely removed.

J. H. TEGMEYER,
Baltimore, Md.

Inconsistencies in punctuation have been corrected without note. Inconsistent hyphenation is as per the original.

Contributions from
The Museum of History and Technology:
Paper 37

Screw-Thread Cutting by the
Master-Screw Method Since 1480

Edwin A. Battison

Edwin A. Battison

SCREW-THREAD CUTTING BY THE
MASTER-SCREW METHOD SINCE 1480

Among the earliest known examples of screw-thread cutting machines are the screw-cutting lathe of 1483, known only in pictures and drawings, and an instrument of the traverse-spindle variety for threading metal, now in the Smithsonian Institution, dating from the late 17th or early 18th century. The author shows clearly their evolution from something quite specialized to the present-day tool. He has traced the patents for these instruments through the early 1930’s and from this research we see the part played by such devices in the development of the machine-tool industry.

The Author: Edwin A. Battison is associate curator of mechanical and civil engineering in the Smithsonian Institution’s Museum of History and Technology.

Directness and simplicity characterize pioneer machine tools because they were intended to accomplish some quite specialized task and the need for versatility was not apparent. History does not reveal the earliest forms of any primitive machines nor does it reveal much about the various early stages in evolution toward more complex types. At best we have discovered and dated certain developments as existing in particular areas. Whether these forms were new at the time they were first found or how widely dispersed such forms may have been is unknown. Surviving evidence is in the form of pictures or drawings, such as the little-known screw-cutting lathe of 1483 (fig. 1) shown in Das mittelalterliche Hausbuch.

This lathe shows that its builder had a keen perception of the necessary elements, reduced to bare essentials, required to accomplish the object. Present are the coordinate slides often credited to Henry Maudslay. His slides are not, of course, associated with the spindle; neither is there any natural law which compels them to guide the tool exactly parallel with the axis of revolution. In this sense the screw-cutting lathe in the Hausbuch is superior because it is in harmony with natural law and can generate a true cylinder, whereas Maudslay’s lathe can only transfer to the work whatever accuracy is built into it.

In principle this machine shown in the Hausbuch is very advanced as we see when we follow the design through to the present time. The artist, whose drawings give us our only knowledge of the machine, himself was obviously not very familiar with the details of its function. Reference to figure 1 shows that the threads on the lead screw and on the work, wind in opposite directions. This must be an error in delineation since the two are closely coupled together without any intervening mechanism so that the only possible result on the work must be a thread winding in the same direction as on the original screw. The work also is shown threaded for its entire length; this cannot be accomplished with any one location of the cross-slide. We are left with the question of whether this slide was used in two locations or whether the artist, possibly working from notes or an earlier rough sketch, failed to show an unthreaded portion on one end or the other of the work.

Figure 1.—Earliest representation found of a master-screw type of thread-cutting machine. From the inconsistencies, such as right- and left-hand threads on master and work, it appears that the artist had scant insight into actual function. From plate 62 of Das mittelalterliche Hausbuch, nach dem Originale im Besitze des Fürsten von Waldburg-Wolfegg-Waldsee, im Auftrage des Deutschen Vereins für Kunstwissenschaft, herausgegeben von Helmuth Th. Bossert und Willy F. Storck (Leipzig: E. A. Seemann, 1912).

Of at least equal importance with the lead screw and work and their relationship to each other is the tool-support with its screw-adjusted cross-slide (fig. 2). Just how this was attached to the frame of the machine so that it placed the tool at a suitable radius is again a questionable point. The very well-developed cutting tool is sharpened to a thin, keen edge totally unsuited for cutting metal but ideal for use on a softer, fibrous substance: undoubtedly wood, in this instance. Unfortunately, the angle at which the artist chose to show us this cutter is not a view from which it is possible to judge whether or not the tool has been made to conform to the helix angle of the thread to be cut. This cross-slide, in conjunction with the traversing work spindle, gives us a machine having two coordinate slides yielding the same effect as the slide rest usually attributed to Henry Maudslay at the end of the 18th century. Actually, an illustration of coordinate slides independent of the spindle had been published as early as 1569 by Besson and knowledge of them widely disseminated by his popular work on mechanics. These slides are shown as part of a screw-cutting machine with a questionably adequate connection, by means of cords, between the master screw and the work.

It was the author’s pleasure recently to obtain for the Smithsonian Institution and identify a small, nicely made, brass instrument which had been in two collections in this country and one collection in Germany as an unidentified locksmith’s tool (fig. 3). This proved to be an instrument of the traverse-spindle variety for threading metal. Fortunately, all essential details were present including a cutter (A in figure 4); this instrument was identified by the signature “Manuel Wetschgi, Augspurg.” The Wetschgis were a well-known family of gunsmiths and mechanics in Augsburg through several generations. Two bore the given name Emanuel: the earlier was born in 1678 and died in 1728. He was quite celebrated in his field of rifle making and became chief of artillery to the Landgrave of Hesse-Kassel shortly before his death in his 51st year. Little is known of the later Emanuel Wetschgi except that he was at Augsburg in 1740. Tentative attribution of the instrument has been made to the earlier Emanuel, chiefly on the basis of his recognized position as an outstanding craftsman.

Figure 2.—Cross-slide for the thread-cutting lathe of Das mittelalterliche Hausbuch, shown in figure 1. It is remarkable not only for its early date, but also for its high state of development with a crossfeed screw which had not become universally accepted 300 years later. The cutter, shown out of its socket, is obviously sharpened for use on wood.

In several respects this little machine differs from its predecessor of the Hausbuch, as might be expected when allowance is made for the generations of craftsmen who undoubtedly worked with such tools over the roughly 200 years of time separating them. Another factor to consider when comparing these two machines is that one was used on metal, the other probably only on wood. Therefore, it is not surprising to find on the later machine an outboard or “tailstock” support for the work. The spindle of this support has to travel in unison with the work-driving spindle so that it is not an unexpected discovery to find that it is spring-loaded. Figure 5 shows how this spring may be adjusted to accommodate various lengths of work by moving the attachment screw to various holes in both the spring and in the frame. Also visible in the same illustration is a rectangular projection at the other end of the spring which engages a mating hole in the “tailstock” spindle to prevent its rotation.

Figure 3.—Small thread-cutting lathe which was made to be held in a vise during use. It was found as shown here, with only the operating crank missing. The overall length is approximately 12 inches, depending on the adjustment of parts. (Smithsonian photo 46525B.)

Figure 6 shows the traversing spindle and nut removed from the machine. Provision has been made for doing this so easily that there is every reason to believe that, originally, there were various different spindle and nut units which could be interchangeably used in the machine. Additional evidence tending to support this concept exists in the cutting tool (fig. 4), which must have been intended for serious work as it has been carefully fitted in its unsymmetrical socket. The cutting blade of this tool, which works with a scraping rather than a true cutting action, is too wide to form a properly proportioned thread when used with the existing lead screw. This may well indicate that the tool was made for use with a lead of coarser pitch, now lost.

Figure 4.—The working area of figure 3, showing the tool and signature. (Smithsonian photo 46525A.)

Perhaps the most startling feature of this machine when compared with the machine of the Hausbuch, is the absence of a cross-slide for adjusting the tool. Possibly this can be explained by the blunt scraping edge on the tool. In actual use, recently, to cut a sample screw, using a tool similar to the one found in the machine (fig. 7), it was found advantageous to be free of a cross-slide and thus be able to feed the tool into the work by feel rather than by rule, as would be done with a slide rest. In this way, it was possible to thread steel without tearing, as the cutting pressure could readily be felt and the tool could release itself from too heavy a cut. Size on several screws could be repeated by setting the tool to produce the desired diameter when its supporting arm came to rest against the frame of the machine. The screws used in the machine itself were apparently made in just such a way. They were not cut with a die as the thread blends very gradually into the body of the screw without the characteristic marks left by the cutting edges of a die. Threads cut with a single-point tool controlled by a cross-slide usually end even more abruptly than those cut by a die, while it would be quite simple with a machine of the nature we are considering to bring the thread to a gentle tapering end as seen in figure 8 (another view of the screw A in fig. 3) by gradually releasing the pressure necessary to keep the tool cutting as the end of the thread was approached.

Figure 5.—Spring for keeping the follower spindle against the work, showing the method and range of adjustment. Note the rectangular projection to engage a mating socket in the spindle, to prevent spindle rotation. (Smithsonian photo 46525.)

Figure 6.—Work spindle and its nut removed from the machine to illustrate how easily another spindle and nut of different pitch could be substituted. (Smithsonian photo 46525C.)

That machines of this general type having the lead screw on the axis of the work were competitive with other methods and other types of machines over a long period of time may be seen from figures and . The machine, left front in figure 9 and in more intimate detail in figure 10, can be seen to differ little from that shown in Das mittelalterliche Hausbuch of 1483. The double work-support is, of course, a great improvement, while the tool-support is regressive since it lacks a feed screw.

The development of engineering theory, coupled with the rising needs of industry, particularly with the advent of the Industrial Revolution, brought about accelerated development of screw-cutting lathes through the combination of screw-cutting machines with simple lathes as seen in figure 9 and in detail in figure 11. One important advance shown here is driving the machine by means of a cord or band so that any means of rotary power could be applied, not just hand or foot power. Of greater interest and technical importance to this study is the provision, seen to better advantage in figure 11, for readily changing from one master lead screw to another. This had already been achieved in the Manuel Wetschgi machine, as far as versatility is concerned, although not in quite such a convenient way.

Figure 7.—Thread of modern form recently cut, using the old screw and nut but with a new tool. The material threaded is carbon-steel drill rod. (Smithsonian photo 49276A.)

Figure 12, the headstock of another and more advanced lathe than shown in figures and but of the same type, shows “keys” (D), each of which is a partial nut of different pitch to engage with a thread of mating pitch. The dotted lines in figure 13 show the engaged and disengaged positions of one of these keys, and figure 14 shows the spindle with the various leads, C. At D is a grooved collar to be engaged by the narrow key shown in operating position at the left in figure 12 for the purpose of controlling the endwise movement of the spindle when used for ordinary turning instead of thread-cutting. In return for greater convenience and freedom from the expense of the many separate spindles, as typified by the Wetschgi machine, a sacrifice has been made in the length of the thread which can be cut without interruption.

Figure 8.—Binding screw seen at A in figure 3, showing the long smooth fadeout of the thread below the shoulder. (Smithsonian photo 49276.)

Figure 9.—Making screws in France in the third quarter of the 18th century. From L’Encyclopédie, ou dictionnaire raisonné des sciences, des arts et des métiers … receuil de planches sur les sciences, les arts libéraux, et les arts méchaniques, avec leur explication (Paris: 1762-1772), vol. 9, plate 1.

Figure 10.—Details of the machine in the left foreground of figure 9, showing the crude tool-support without screw adjustment. From L’Encyclopédie, vol. 9, plate 2.

This reduction in the length that could conveniently be threaded was no great drawback on many classes of work. This can be realized from figure 16 which shows a traverse-spindle lathe headstock typical of the mid-19th century. During the years intervening between the machines of figures and , the general design was greatly improved by removing the lead screws from the center of the spindle. This made possible a shorter, much stiffer spindle and supported both ends of the spindle in one frame or headstock rather than in separate pieces attached to the bed. The screws were now mounted outside of the spindle-bearings, one at a time, while the mating nuts were cut partially into the circumference of a disk which could be turned to bring any particular nut into working position as required. With this arrangement, a wide variety of leads either right or left hand could be provided and additional leads could be fitted at any future time. Screw-cutting lathes of this design were popular for a very long time with instrument makers and opticians who had little need to cut screws of great length.

Figure 11.—Details of the threading lathe seen in the right foreground of figure 9 showing the method of drive and support for the work. From L’Encyclopédie, vol. 9, plate 1.

The demands of expanding industry for greater versatility in the production of engineering elements late in the 18th century set the stage for the evolution of more complex machines tending to place the threaded spindle lathes in eclipse. Maudslay’s lathe of 1797-1800 (fig. 15) appeared at this time when industry was receptive to rapid innovation. Unfortunately, the gearing which once existed to connect the headstock spindle with the lead screw has long been lost. At this time it is quite difficult to say with certainty whether the original gear set offered a variety of ratios, as was true of slightly later Maudslay lathes, or a fixed ratio. The plausibility of the fixed ratio theory is supported by the very convenient means, seen in figure 15, for removing the lead screw in preparation for substitution of one of another pitch. All that is required is to back off its supporting center at the tailstock end and withdraw the screw from its split nut and from the driving clutch near the headstock. This split nut also would have to be changed to one of a pitch corresponding to that of the screw. While more expensive than a solid nut, it neatly circumvents the need (and saves the time involved) to reverse the screw in order to get the tool back to the point of beginning preliminary to taking another cut. David Wilkinson’s lathe of 1798 (fig. 17) which was developed in Rhode Island at the same time shows the same method of mounting and driving the master screw. At least in the United States, this method of changing the lead screw instead of using change gears remained popular for many years. Examples of this changeable screw feature are to be found in the lathes constructed for the pump factory of W. & B. Douglas Company, Middletown, Connecticut, in the 1830’s. Middletown, at that time one of the leading metal-working centers in one of the chief industrial States, had been for many years the site of the Simeon North arms factory which rivaled Whitney’s. In this atmosphere, it is reasonable to expect that machinery constructed by local mechanics, as was the custom in those days, would reflect the most accepted refinements in machine design.

Figure 12.—Well-developed example of lathe headstock having several leads on the spindle and provision for mounting the work or a work-holding chuck on the spindle. Adapted from L’Encyclopédie, vol. 10, plate 13.

Figure 13.—End view of the headstock seen in figure 12, showing the keys or half nuts which engage the threaded spindle, in engaged and disengaged positions. From L’Encyclopédie, vol. 10, plate 13.

Figure 14.—Spindle of figures and , showing the several leads and the many-sided seat for the driving pulley. Note the scale of feet. From L’Encyclopédie, vol. 10, plate 16.

Roughly twenty years later, Joseph Nason of New York patented the commercially very important “Fox” brassworker’s lathe (fig. 18). While this does have a ratio in the pair of gears connecting the work spindle and master screw, it is clear from the patent that various pitches are to be obtained by changing screws, not by changing gears. The patent sums it up as follows:

A nut upon the end of the stud … is unscrewed when the guide screw is to be removed or changed. The two wheels … should have in their number of teeth a common multiple. They are seldom or never removed and their diameters are made dissimilar only for the purpose of giving to the guide screw a slower rate of motion than that of the mandrel whereby it may be made of coarser pitch than that of the screw to be cut and its wear materially lessened.

The introduction of gearing between the spindle and the lead screw, for whatever purpose, could not help but introduce variable factors caused by inaccuracies in the gears themselves and in their mounting. These were of little consequence for common work, particularly when coupled to a screw which, itself, was of questionable accuracy. The increasing refinements demanded in scientific instruments and in machine tools themselves after they had reached a relatively stable form dictated that attention be dedicated to improved accuracy of the threaded components.

Figure 15.—Maudslay’s well-known screw-cutting lathe of 1797-1800, showing the method of mounting and driving changeable master screws. (Photo courtesy of The Science Museum, London.)

Figure 16.—Headstock of a German instrument-maker’s lathe, typical of the mid-19th century, showing the traverse spindle, interchangeable lead screws, and semicircumferential nut containing several leads. The nut may be brought into engagement by the lever at top rear of the headstock. This releases the end thrust control on the spindle simultaneously with engagement of the nut. (Smithsonian photo 49839.)

Figure 17.—David Wilkinson’s screw-cutting lathe, patented in the United States in 1798. Note the ready facility with which the lead screw may be exchanged for another and the same means of supporting and driving as in figure 15. (U.S. National Archives photo.)

An attack on this problem, which interestingly reverts to the fundamental principle of motion derived from a master screw without the intervention of other mechanism (fig. 19), is covered by a patent issued to Charles Vander Woerd, one-time superintendent of the Waltham Watch Company. The problem is well stated in the patent:

This invention relates to the manufacture of leading screws to be used for purposes requiring the highest attainable degree of correctness in the cutting of the screw-threads of said screw … as, for example, in machines for ruling lines in glass plates to produce refraction [sic] gratings for the resolution of the lines of the solar spectrum, such machines being required to rule many thousands of lines on an inch of space by a marking device which is reciprocated over the glass plate and is fed by the action of a leading screw after the formation of each line. Great difficulty has been experienced in constructing a leading screw for this and other purposes, in which the thread is so nearly correct as to produce no perceptible variation in the microscopic spaces between the ruled lines or gratings…. Various causes prevent the formation of a thread on the rod or blank, which is absolutely uniform and accurate from end to end of the rod. Among other causes are the variations of temperature from time to time, the imperfections of the operating leading screw, the springing of the leading screw and of the rod that is being threaded, and other unavoidable causes, all of which, although apparently trivial and producing only slight variations in the thread at different parts of the rod or blank, are of sufficient moment to be seriously considered when a screw of absolute accuracy is desired.

Figure 18.—Nason’s lathe, patented in 1854, showing a master lead screw driven at less than work speed so that the master could be of a coarser and more durable pitch than the work. U.S. patent 10383.

It is interesting to note in figure 19 that Vander Woerd’s machine, to avoid the problems outlined in his patent, has returned to a starkly simple design. We are not told, however, how he originated this master screw which is used to produce the accurately threaded work pieces. Later generations, in the search for ever-greater accuracy, also returned to the fundamental simplicity of a master screw as we shall see when we consider the refinements in mechanism necessary to the extended development of the automobile and the airplane.

Figure 19.—Vander Woerd’s patent, seen here, covered the combination of a master screw, toolslide and work in a rigid frame to be supported and driven by outside means of no required precision. U.S. patent 293930 dated February 1884.

As the power and speed of automobiles and aircraft increased, critical parts became more highly stressed. Gears and threaded parts were particularly troublesome details of the mechanism because of the stresses concentrated in them, and, in the case of gears, because of the internal and external stresses originating in minute deviations from the ideal of tooth form and spacing. The problems were not entirely new but had hitherto been solved by increasing the size of the parts, an avenue of limited utility to designers in these fields where total weight as well as the effects of mass and inertia are so important. By making these parts of heat-treated steel, the strength could be made suitable while the size and mass of the parts were kept within bounds. The necessary processes of heat-treating were not always applicable to finished parts as they sometimes destroyed both finish and accuracy. Grinding, which was well developed for the simple plane, cylindrical, and conical surfaces so widely used in mechanisms, had to be extended to threads and gears so that they could be finished after heat-treating. Sometimes the gear teeth themselves were ground; for other applications it was sufficient to improve the accuracy of the gear cutters.

Figure 20.—A hob-grinding machine patented in 1932 and incorporating the master-screw principle. Carl G. Olson’s U.S. patent 1874592.

Attempts to produce gear hobs free of the imperfections and distortions introduced by heat treatment led to another return to the use of the master lead screw. Figure 20 illustrates a machine having this feature which was patented in 1932 by Carl G. Olson. In speaking of the spindle-driving mechanism disclosed in earlier patents, the patent goes on to say:

This driving mechanism includes an integral spindle 20, one extremity thereof being designed for supporting a hob 22 and the other extremity thereof being formed so as to present a lead screw 24. The spindle 20 is mounted between a bearing 26 and a bearing 28, the latter bearing providing a nut in which the lead screw 24 rotates…. From the description thus far given it will be apparent that the rotation of the lead screw 24 within the bearing or nut 28 will cause the hob to be moved axially, the lead of the screw 24 being equal to the lead of the thread in the hob.

Claim 8 which concludes the descriptive portion of the patent states in part:

In a hob grinding machine of the class described, a rotary work supporting spindle, means for effecting longitudinal movement of the spindle, a tool holder for supporting a grinding wheel in operative position with respect to the work supported by the spindle during the rotary and longitudinal movement thereof, …

Even before this patent was applied for, another patent was pending for the purpose of modifying the pitch of the lead screw without the use of change gears in spite of the wide acceptance of such gear mechanisms for over a hundred years.

Figure 21.—A hob-grinding machine of 1933, showing use of the master screw with a modifier but without change gears. Carl G. Olson’s U.S. patent 1901926.

Figure 22.—A sine-bar device to modify the effective lead of a master lead screw without introducing a complex mechanism which would be both difficult to make and to operate within the required close limits. Carl G. Olson’s (1933) U.S. patent 1901926.

Figure 21 shows a plan view of the machine, and figure 22 a detailed view of the sine-bar mechanism actuated by the master screw, 6, to modify the effective pitch of the lead screw in accordance with the realities of practice as stated in the preamble of the patent:

This invention relates to material working machines, and particularly to machines such as hob grinders and the like, wherein the work is reciprocated through the agency of a lead screw.

In the manufacture of hobs it is common practice to employ the same machine for grinding hobs of varied diameters, and in order to employ such a machine in this manner the pitch of the lead screw, thereof, which actuates the work carrier, must conform to the axial pitch of the hob to be ground. This will be readily apparent when it is understood that the helix angles of hobs vary in accordance with their diameters and, consequently, the difference between the normal pitch and the axial pitch correspondingly varies. While the requirement for the normal pitch may be the same for hobs of different diameters, it is necessary to change the axial pitch in accordance with a change in the hob diameter, and this axial pitch of the hob is equal to the pitch of the lead screw which actuates the work carrier in grinding machines heretofore used. Hence, in order to adapt such machines to cover a wide range of leads, it is necessary to provide a large number of interchangeable lead screws and obviously this represents a large investment, and the interchanging of these screws requires the expenditure of considerable time in setting up the machine for each job.

Thread-grinding machines were being designed concurrent with the development of hob-grinding machines. Many were entirely concerned with features peculiar to the problems of wheel-dressing and to automatic characteristics. An invention to embody the use of a master screw and concerned with the precision grinding of worm threads, for use in gearing, was patented by Frederick A. Ward in this era. That part of the invention pertaining to the use of a master screw, “a rotary work holder mounted on said carriage and provided with a driving spindle, an exchangeable master screw and stationary nut detachably secured to said spindle and head, …” is shown in figure 23.

Figure 23.—Details of a work spindle with work, showing the use of a master lead screw to control the pitch of a precision worm thread being ground. From the 1933 U.S. patent 1899654, of F. A. Ward’s worm-grinding machine.

Machines embodying the principle of the master lead screw are found in constant use by industry at the present time for specialized application. Whenever technological changes again reopen the topic of thread-cutting to a new degree of accuracy or call for a reevaluation of popular methods for any other reason, we may expect to see another resurgence of the master-screw method, for no other design eliminates so many variables or rests on such firm and fundamental natural principles as the machine of Das mittelalterliche Hausbuch of 1483, the earliest such machine now known.

Page : “… the spindle, to prevent …” (had “pindle”)

Page : “… servants à l'intelligence de plusieurs choses difficiles, & nécessaires …” (had “a,” “plusiers,” “necessaires”)

"> Contributions from
The Museum of History and Technology:
Paper 38

The Earliest Electromagnetic Instruments

Robert A. Chipman

ELECTROSTATIC INSTRUMENTS BEFORE 1800 123

INSTRUMENTING VOLTAIC OR GALVANIC ELECTRICITY, 1800-1820 124

ELECTRICAL INSTRUMENTATION, 1800-1820 125

OERSTED’S DISCOVERY 126

BEGINNINGS OF ELECTROMAGNETIC INSTRUMENTATION 126

CHRONOLOGY AND PRIORITY 127

ORIGINAL ELECTROMAGNETIC MULTIPLIERS 129

CONCLUSIONS 135

ACKNOWLEDGMENTS 136

INDEX

Figure 1.—Models of various electromagnetic instruments created by Schweigger, Poggendorf and Cumming in 1821, made for an exhibit in the Museum of History and Technology, Smithsonian Institution. (Smithsonian photo 49493.)

Robert A. Chipman

THE EARLIEST ELECTROMAGNETIC INSTRUMENTS

The history of the early stages of electromagnetic instrumentation is traced here through the men who devised the theories and constructed the instruments.

Despite the many uses made of voltaic cells after Volta’s announcement of his “pile” invention in 1800, two decades passed before Oersted discovered the magnetic effects of a voltaic circuit. As a result of this and within a five-month period, three men, apparently independently, announced the invention of the “first” electromagnetic instrument. This article details the merits of their claims to priority.

The Author: Robert A. Chipman is chairman of the Department of Electrical Engineering at the University of Toledo in Toledo, Ohio, and consultant to the Smithsonian Institution.

Electrostatic Instruments before 1800

It is the fundamental premise of instrument-science that a device for detecting or measuring a physical quantity can be based on any phenomenon associated with that physical quantity. Although the instrumentation of electrostatics in the 18th century, for example, relied mainly on the phenomena of attraction and repulsion and the ubiquitous sparks and other luminosities of frictional electricity, even the physiological sensation of electric shock was exploited semiquantitatively by Henry Cavendish in his well-known anticipation of Ohm’s researches. Likewise, Volta in 1800 described at length how the application of his pile to suitably placed electrodes on the eyelids, on the tongue, or in the ear, caused stimulation of the senses of sight, taste and hearing; on the other hand, he reported that electrodes in the nose merely produced a “more or less painful” pricking feeling, with no impression of smell. The discharges from the Leyden jars of some of the bigger frictional machines, such as van Marum’s at Leyden, were found by 1785 to magnetize pieces of iron and to melt long pieces of metal wire.

The useful instruments that emerged from all of this experience were various deflecting “electrometers” and “electroscopes” (the words were not carefully distinguished in use), including the important goldleaf electroscope ascribed to Abraham Bennet in 1787.

In 1786, Galvani first observed the twitching of the legs of a dissected frog produced by discharges of a nearby electrostatic machine, thereby revealing still another “effect” of electricity. He then discovered that certain arrangements of metals in contact with the frog nerves produced the same twitching, implying something electrical in the frog-metal situation as a whole. Although Galvani and his nephew Aldini drew from these experiments erroneous conclusions involving “animal electricity,” which were disputed by Volta in his metal-contact theory, it is significant from the instrumentation point of view that the frog’s legs were unquestionably by far the most sensitive detector of metal-contact electrical effects available at the time. Without their intervention the development of this entire subject-area, including the creation of chemical cells, might have been delayed many years. Volta himself realized that the crucial test between his theory and that of Galvani required confirming the existence of metal-contact electricity by some electrical but nonphysiological detector. He performed this test successfully with an electroscope, using the “condensing” technique he had invented more than a decade earlier.

Instrumenting Voltaic or Galvanic Electricity, 1800-1820

In his famous letter of March 20, 1800, written in French from Como, Italy, to the president of the Royal Society in London, Volta made the first public announcement of both his “pile” (the first English translator used the word “column”), and his “crown of cups” (the same translator used “chain of cups” for Volta’s “couronne de tasses”). The former consisted of a vertical pile of circular disks, in which the sequence copper-zinc-pasteboard, was repeated 10 or 20 or even as many as 60 times, the pasteboard being moistened with salt water. The “crown of cups” could be most conveniently made with drinking glasses, said Volta, with separated inch-square plates of copper and zinc in salt water in each glass, the copper sheet in one glass being joined by some intermediate conductor and soldered joints to the zinc in the next glass.

Volta considered the “crown of cups” and the “pile” to be essentially identical, and as evidences of the electrical nature of the latter, said:

… if it contains about 20 of these stories or couples of metal, it will be capable not only of emitting signs of electricity by Cavallo’s electrometer, assisted by a condenser, beyond 10° or 15°, and of charging this condenser by mere contact so as to make it emit a spark, etc., but of giving to the fingers with which its extremities (the bottom and top of the column) have been touched several small shocks, more or less frequent, according as the touching has been repeated. Each of these shocks has a perfect resemblance to that slight shock experienced from a Leyden flask weakly charged, or a battery still more weakly charged, or a torpedo in an exceedingly languishing state, which imitates still better the effects of my apparatus by the series of repeated shocks which it can continually communicate.

The “effects” provided by Volta’s pile and crown-of-cups are therefore electroscope deflection, sparks, and shocks. Later in the letter, he describes the stimulation of sight, taste, and hearing as noted earlier, but nowhere does he mention chemical phenomena of any kind, or the heating of a wire joining the terminals of either device. Hence, except for the additional physiological responses, he adds nothing to the catalog of observations on which instruments might be based. His familiarity with the moods of the torpedo (electric eel) seems to be intimate.

The reading of Volta’s letter to the Royal Society on June 26, 1800, its publication in the Society’s Philosophical Transactions (in French) immediately thereafter, and its publication in English in the Philosophical Magazine for September 1800, gave scientists throughout Europe an easily constructed and continuously operating electric generator with which innumerable new physical, chemical, and physiological experiments could be made. Editor-engineer William Nicholson read Volta’s letter before its publication and, by the end of April, he and surgeon Anthony Carlisle had built a voltaic pile. Applying a drop of water to improve the “connection” of a wire lying on a metal plate, they happened to notice gas bubbles forming on the wire, and pursued the observation to the point of identifying the electrical decomposition of water into hydrogen and oxygen.

Within two or three years innumerable electrochemical reactions had been described, some of which, one might think, could have served as operating principles for electrical instruments. Although the phenomena of gas formation and metal deposition were in fact widely used as crude indicators of the polarity and relative strength of voltaic piles and chemical cells during the period 1800-1820 (and the gas bubbles were made the basis of a telegraph receiver by S. T. Soemmering), the quantitative laws of electrolysis were not worked out by Faraday until after 1830, and not until 1834 was he satisfied that the electrolytic decomposition of water was sufficiently well understood to be made the basis for a useful measuring instrument. Describing his water-electrolysis device in that year, he wrote:

The instrument offers the only actual measurer [italics his] of voltaic electricity which we at present possess. For without being at all affected by variations in time or intensity, or alterations in the current itself, of any kind, or from any cause, or even of intermissions of actions, it takes note with accuracy of the quantity of electricity which has passed through it, and reveals that quantity by inspection; I have therefore named it a VOLTAELECTROMETER.

In passing, Faraday commented that the efforts by Gay-Lussac and Thenard to use chemical decomposition as a “measure of the electricity of the voltaic pile” in 1811 had been premature because the “principles and precautions” involved were not then known. He also noted that the details of metal deposition in electrolysis were still not sufficiently understood to permit its use in an instrument.