Glossary of Geological and Other Scientific Terms Used in This Work

Acephalous. The Acephala are that division of molluscous animals which, like the oyster and scallop, are without heads. The class Acephala of Cuvier comprehends many genera of animals with bivalve shells, and a few which are devoid of shells. Etym., α, a, without, and κεφαλη, cephale, the head.
Acidulous. Slightly acid.
Acrogens. One of five classes into which all plants may be divided; it includes such flowerless ones as grow from the top only, and whose stems consequently do not increase materially in bulk, as Mosses, Ferns, Lycopodiums, Equisetums, &c. The trunk of a tree fern is a good example. They are also called Acrobrya. Etym., ακρον, acron, the top, and γενεσις, genesis, increase.
Adipocire. A substance apparently intermediate between fat and wax, into which dead animal matter is converted when buried in the earth, and in a certain stage of decomposition. Etym., adeps, fat, and cera, wax.
Albite. See "Felspar."
Alembio. An apparatus for distilling.
Algæ. An order or division of the cryptogamic class of plants. The whole of the sea-weeds are comprehended under this division, and the application of the term in this work is to marine plants. Etym., alga, sea-weed.
Alluvial. The adjective of alluvium, which see.
Alluvion. Synonymous with alluvium, which see.
Alluvium. Earth, sand, gravel, stones, and other transported matter which has been washed away and thrown down by rivers, floods, or other causes upon land not permanently submerged beneath the waters of lakes or seas. Etym., alluo, to wash upon, or alluvio, an inundation.
Alum-stone, Alumen, Aluminous. Alum is the base of pure clay, and strata of clay are often met with containing much iron pyrites. When the latter substance decomposes, sulphuric acid is produced, which unites with the aluminous earth of the clay to form sulphate of alumine, or common alum. Where manufactories are established for obtaining the alum, the indurated beds of clay employed are called Alum-stone.
Ammonite. An extinct and very numerous genus of the order of molluscous animals called Cephalopoda, allied to the modern genus Nautilus, which inhabited a chambered shell, curved like a coiled snake. Species of it are found in all geological periods of the secondary strata; but they have not been seen in the tertiary beds. They are named from their resemblance to the horns on the statues of Jupiter Ammon.
Amorphous. Bodies devoid of regular form. Etym., α, a, without, and μορφη, morphe, form.
Amygdaloid. One of the forms of the Trap-rocks, in which agates and simple minerals appear to be scattered like almonds in a cake. Etym., αμυγδαλα, amygdala, an almond.
Analcime. A simple mineral of the Zeolite family, also called Cubizite, of frequent occurrence in the Trap-rocks.
Analogue. A body that resembles or corresponds with another body. A recent shell of the same species as a fossil shell is the analogue of the latter.
Angoiosperms. A term applied to all flowering plants in which the ovules are inclosed in an ovary, and the seeds in a pericarp or covering, as in all flowering plants except those mentioned under gymnosperms and gymnogens, which see. Etym., αγγος, angos, a vessel, and σπερμα, a seed.

Anoplotherium. A fossil extinct quadruped belonging to the order Pachydermata, resembling a pig. It has received its name because the animal must have been singularly wanting in means of defence, from the form of its teeth and the absence of claws, hoofs, and horns. Etym., ανοπλος, anoplos, unarmed, and θηριον, therion, a wild beast.
Antagonist Power. Two powers in nature, the action of the one counteracting that of the other, by which a kind of equilibrium or balance is maintained, and the destructive effect prevented that would be produced by one operating without a check.
Antennæ. The articulated horns with which the heads of insects are invariably furnished.
Anthracite. A shining substance like black-lead; a species of mineral charcoal. Etym., ανθραξ, anthrax, coal.
Anthracotherium. A name given to an extinct quadruped, supposed to belong to the Pachydermata, the bones of which were first found in lignite and coal of the tertiary strata. Etym., ανθραξ, anthrax, coal, and θηριον, therion, wild beast.
Anthropomorphous. Having a form resembling the human. Etym., ανθρωπος, anthropos, a man, and μορφη, morphe, form.
Antiseptic. Substances which prevent corruption in animal and vegetable matter, as common salt does, are said to be antiseptic. Etym., αντι, anti, against, and σηπω, sepo, to putrefy.
Arenaceous. Sandy. Etym., arena, sand.
Argillaceous. Clayey, composed of clay. Etym., argilla, clay.
Arragonite. A simple mineral, a variety of carbonate of lime, so called from having been first found in Aragon in Spain.
Atolls. Coral islands of an annular form, or consisting of a circular strip or ring of coral surrounding a central lagoon.
Augite. A simple mineral of a dark green, or black color, which forms a constituent part of many varieties of volcanic rocks. Name applied by Pliny to a particular mineral, from the Greek αυγη, auge, lustre.

Avalanches. Masses of snow which, being detached from great heights in the Alps, acquire enormous bulk by fresh accumulations as they descend; and when they fall into the valleys below often cause great destruction. They are also called lavanges and lavanches in the dialects of Switzerland.

Basalt. One of the most common varieties of the Trap-rocks. It is a dark green or black stone, composed of augite and felspar, very compact in texture, and of considerable hardness, often found in regular pillars of three or more sides called basaltic columns. Remarkable examples of this kind are seen at the Giant's Causeway, in Ireland, and at Fingal's Cave, in Staffa, one of the Hebrides. The term is used by Pliny, and is said to come from basal, an Æthiopian word signifying iron. The rock often contains much iron.
Basin" of Paris, "Basin" of London. Deposits lying in a hollow or trough, formed of older rocks; sometimes used in geology almost synonymously with "formations," to express the deposits lying in a certain cavity or depression in older rocks.
Belemnite. An extinct genus of the order of molluscous animals called Cephalopoda, having a long, straight, and chambered conical shell. Etym., βελεμνον, belemnon, a dart.
Bitumen. Mineral pitch, of which the tar-like substance which is often seen to ooze out of the Newcastle coal when on the fire, and which makes it cake, is a good example. Etym., bitumen, pitch.
Bituminous Shale. An argillaceous shale, much impregnated with bitumen, which is very common in the Coal Measures.
Blende. A metallic ore, a compound of the metal zinc with sulphur. It is often found in brown shining crystals; hence its name among the German miners, from the word blenden, to dazzle.
Bluffs. High banks presenting a precipitous front to the sea or a river. A term used in the United States of North America.
Botryoidal. Resembling a bunch of Grapes. Etym., βοτρυς, botrys, a bunch of grapes, and ειδος, eidos, form.

Boulders. A provincial term for large rounded blocks of stone lying on the surface of the ground, or sometimes imbedded in loose soil, different in composition from the rocks in their vicinity, and which have been therefore transported from a distance.

Breccia. A rock composed of angular fragments connected together by lime or other mineral substance. An Italian term.

Calc Sinter. A German name for the deposits from springs holding carbonate of lime in solution—petrifying springs. Etym., kalk, lime, and sintern, to drop.
Calcaire Grossier. An extensive stratum, or rather series of strata, found in the Paris Basin, belonging to the Eocene tertiary period. Etym., calcaire, limestone, and grossier, coarse.
Calcareous Rock. Limestone. Etym., calx, lime.
Calcareous Spar. Crystallized carbonate of lime.
Carbon. An undecomposed inflammable substance, one of the simple elementary bodies. Charcoal is almost entirely composed of it. Etym., carbo, coal.
Carbonate of Lime. Lime combines with great avidity with carbonic acid, a gaseous acid only obtained fluid when united with water,—and all combinations of it with other substances are called Carbonates. All limestones are carbonates of lime, and quicklime is obtained by driving off the carbonic acid by heat.
Carbonated Springs. Springs of water, containing carbonic acid gas. They are very common, especially in volcanic countries; and sometimes contain so much gas, that if a little sugar be thrown into the water it effervesces like soda-water.
Carbonic Acid Gas. A natural gas which often issues from the ground, especially in volcanic countries. Etym., carbo, coal; because the gas is obtained by the slow burning of charcoal.
Carboniferous. A term usually applied, in a technical sense, to an ancient group of secondary strata; but any bed containing coal may be said to be carboniferous. Etym., carbo, coal, and fero, to bear.
Cataclysm. A deluge. Etym., κατακλυζω, catacluzo, to deluge.
Cephalopoda. A class of molluscous animals, having their organs of motion arranged round their head. Etym., κεφαλη, cephale, head, and ποδα, poda, feet.
Cetacea. An order of vertebrated mammiferous animals inhabiting the sea. The whale, dolphin, and narwal are examples. Etym., cete, whale.
Chalcedony. A siliceous simple mineral, uncrystallized. Agates are partly composed of chalcedony.
Chalk. A white earthy limestone, the uppermost of the secondary series of strata.
Chert. A siliceous mineral, nearly allied to chalcedony and flint, but less homogeneous and simple in texture. A gradual passage from chert to limestone is not uncommon.
Chloritic Sand. Sand colored green by an admixture of the simple mineral chlorite. Etym., χλωρυς, chlorus, green.
Cleavage. Certain rocks, usually called Slate-rocks, may be cleaved into an indefinite number of thin laminæ which are parallel to each other, but which are generally not parallel to the planes of the true strata or layers of deposition. The planes of cleavage, therefore, are distinguishable from those of stratification.
Clinkstone, called also phonolite, a felspathic rock of the trap family, usually fissile. It is sonorous when struck with a hammer, whence its name.
Coal Formation. This term is generally understood to mean the same as the Coal Measures, or Carboniferous group.
Coleoptera. An order of insects (Beetles) which have four wings, the upper pair being crustaceous and forming a shield. Etym., κολεος, coleos, a sheath, and πτερον, pteron, a wing.
Conformable. When the planes of one set of strata are generally parallel to those of another set which are in contact, they are said to be conformable. Thus the set a, b, Fig. 98, rest conformably on the inferior set c, d; but c, d rest unconformably on E.

Congeners. Species which belong to the same genus.
Conglomerate, or Puddingstone. Rounded water-worn fragments of rock or pebbles, cemented together by another mineral substance, which may be of a siliceous, calcareous, or argillaceous nature. Etym., con, together, glomero, to heap.
Coniferæ. An order of plants, all of which have disks in their wood fibres, by which they are recognized in a fossil state. Their ovules are naked (see Gymnogens). Most of the northern kinds bear the seeds in cones; but the yew does not, nor do a host of tropical and south temperate species. Etym., conus, a cone, and fero, to bear.
Cosmogony, Cosmology. Words synonymous in meaning, applied to speculations respecting the first origin or mode of creation of the earth. Etym., κοσμος, kosmos, the world, and γονη, gonee, generation, or λογος, logos, discourse.
Crag. A provincial name in Norfolk and Suffolk for certain tertiary deposits usually composed of sand with shells, belonging to the Older Pliocene period.
Crater. The circular cavity at the summit of a volcano, from which the volcanic matter is ejected. Etym., crater, a great cup or bowl.
Cretaceous. Belonging to chalk. Etym., creta, chalk.
Crop Out. A miner's or mineral surveyor's term, to express the rising up or exposure at the surface of a stratum or series of strata.
Crust of the Earth. See "Earth's crust."
Crustaceous. Animals having a shelly coating or crust which they cast periodically. Crabs, shrimps, and lobsters are examples.
Cryptogamic. Asexual, flowerless, or Acotyledonous plants; a term applied to half the vegetable kingdom in contradistinction to Phænogamic, sexual, or flowering plants. It includes Fungi, Sea-weeds, Lichens, Mosses, Ferns, &c., which have no obvious flowers, and no cotyledons (seed-lobes) to their spores or seeds. Etym., κρυπτος, cruptos, concealed, and γαμος, gamos, marriage.
Crystals. Simple minerals are frequently found in regular forms, with facets like the drops of cut glass of chandeliers. Quartz being often met with in rocks in such forms, and beautifully transparent like ice, was called rock-crystal, κρυσταλλος, crystallos, being Greek for ice. Hence the regular forms of other minerals are called crystals, whether they be clear or opake.
Crystallized. A mineral which is found in regular forms or crystals is said to be crystallized.
Crystalline. The internal texture which regular crystals exhibit when broken, or a confused assemblage of ill-defined crystals. Loaf-sugar and statuary-marble have a crystalline texture. Sugar-candy and calcareous spar are crystallized.
Cupriferous. Copper-bearing. Etym., cuprum, copper, and fero, to bear.
Cycadeæ. A small and very anomalous order of flowering plants, chiefly found in Mexico, the East Indian Islands, South Africa, and Australia. They are Gymnogens as to ovules, and neither Exogens nor Endogens in the wood of their short, simple, or branched trunks, and they have dicotyledonous seeds. The leaves are pinnated (like those of cocoa-nut palms), and when young are rolled inwards as in Ferns. The wood fibres are curiously perforated, and marked, by which they are recognized in a fossil state as well as by the trunk and foliage, and the cones, which contain the male flowers. The term is derived from κυκας, cycas, a name applied by the ancient Greek naturalist Threophrastus to a palm.

Cyperaceæ. A tribe of plants answering to the English sedges; they are distinguished from grasses by their stems being solid, and generally triangular, instead of being hollow and round. Together with Gramineæ, they constitute what writers on botanical geography often call glumaceæ.

Debacle. A great rush of waters, which, breaking down all opposing barriers, carries forward the broken fragments of rocks, and spreads them in its course. Etym., débacler, French, to unbar, to break up as a river does at the cessation of a long-continued frost.
Delta. When a great river, before it enters the sea, divides into separate streams, they often diverge and form two sides of a triangle, the sea being the base. The land included by the three lines, and which is invariably alluvial, was first called, in the case of the Nile a delta, from its resemblance to the letter of the Greek alphabet which goes by that name Δ. Geologists apply the term to alluvial land formed by a river at its mouth, without reference to its precise shape.
Denudation. The carrying away by the action of running water of a portion of the solid materials of the land, by which inferior rocks are laid bare. Etym., denudo, to lay bare.
Deoxidized, Deoxidated. Deprived of oxygen. Disunited from oxygen.
Desiccation. The art of drying up. Etym., desicco, to dry up.
Detritus. Matter worn or rubbed off from rocks. Etym., de, from, and tero, to rub.
Dicotyledonous. A grand division of the vegetable kingdom, founded on the plant having two cotyledons, or seed-lobes. Etym., δις, dis, double, and κοτυληδον, cotyledon.
Dikes. When a mass of the unstratified or igneous rocks, such as granite, trap, and lava, appears as if injected into a rent in the stratified rocks, cutting across the strata, it forms a dike. They are sometimes seen running along the ground, and projecting, like a wall, from the softer strata on both sides of them having wasted away; whence they were first called in the north of England and in Scotland dikes, a provincial name for wall. It is not easy to draw the line between dikes and veins. The former are generally of larger dimensions, and have their sides parallel for considerable distances; while veins have generally many ramifications, and these often thin away into slender threads.
Diluvium. Those accumulations of gravel and loose materials, which, by some geologists, are said to have been produced by the action of a diluvian wave or deluge sweeping over the surface of the earth. Etym., diluvium, deluge.
Dip. When a stratum does not lie horizontally, but is inclined, it is said to dip towards some point of the compass, and the angle it makes with the horizon is called the angle of dip or inclination.
Diptera. An order of insects, comprising those which have only two wings. Etym., δις, dis, double, and πτερον, pteron, wing.
Dolerite. One of the varieties of the Trap-rocks, composed of augite and felspar.
Dolomite. A crystalline limestone, containing magnesia as a constituent part. Named after the French geologist Dolomieu.

Dunes. Low hills of blown sand that skirt the shores of Holland, England, Spain, and other countries.

Earth's Crust. Such superficial parts of our planet as are accessible to human observation.
Eopyrosis. A Greek term for a destruction by fire.
Elytra. The wing-sheaths, or upper crustaceous membranes, which form the superior wings in the tribe of beetles. They cover the body, and protect the true membranous wing. Etym., ελυτρον, elytron, a sheath.
Endogens. A class of flowering plants, whose stems present no distinction of wood, pith, and bark. The wood is disposed in bundles, placed nearer the axis than those of the previous year, as in palm trunks. This class answers to the Monocotyledones of Jussieu. Etym., ενδον, endon, within, and γενεσις, genesis, increase.
Entomostraca. Cuvier's second section of Crustacea; so called from their relationship to insects. Etym., εντομα, entoma, insects.
Eocene. A name given to the lowest division of the tertiary strata, containing an extremely small percentage of living species amongst its fossil shells, which indicate the first commencement or dawn of the existing state of the animate creation. Etym., ηως, eos, aurora or the dawn, and καινος, kainos, recent.
Escarpment. The abrupt face of a ridge of high land. Etym., escarper, French, to cut steep.
Estuaries. Inlets of the land, which are entered both by rivers and the tides of the sea. Thus we have the estuaries of the Thames, Severn, Tay, &c. Etym., æstus, the tide.
Exogens. A class of flowering plants whose stems have bark, wood, and pith. The bark is increased by layers deposited within the previously formed layers and the wood of layers or rings placed outside of those of the previous year. This class answers to the Dicotyledones of Jussieu, and includes all common English trees except pines, &c. (See Gymnogens.) Etym., εξο, exo, outside, γενεσις, genesis, increase.
Experimentum Crucis. A decisive experiment, so called, because, like a cross or direction-post, it directs men to true knowledge; or, as some explain it, because it is a kind of torture whereby the nature of the thing is extorted, as it were, by violence.

Exuviæ. Properly speaking, the transient parts of certain animals which they put off or lay down to assume new ones, as serpents and caterpillars shift their skins; but in geology it refers not only to the cast-off coverings of animals, but to fossil shells and other remains which animals have left in the strata of the earth. Etym., exuere, to put off or divest.

Faluns. A French provincial name for some tertiary strata abounding in shells in Touraine, which resemble in lithological characters the "Crag" of Norfolk and Suffolk.
Fault, in the language of miners, is the sudden interruption of the continuity of strata in the same plane, accompanied by a crack or fissure, varying in width from a mere line to several feet, which is generally filled with broken stone, clay, &c. The strata, a, b, c, &c., must at one time have been continuous; but a fracture having taken place at the fault F, either by the upheaving of the portion A, or the sinking of the portion B, the strata were so displaced that the bed a in B is many feet lower than the same bed a in the portion A.
Fauna. The various kinds of animals peculiar to a country constitute its Fauna, as the various kinds of plants constitute its Flora. The term is derived from the Fauni, or rural deities, in Roman Mythology.
Felspar. A simple mineral, which, next to quartz, constitutes the chief material of rocks. The white angular portions in granite are felspar. This mineral always contains some alkali in its composition. In common felspar the alkali is potash; in another variety, called Albite or Cleavlandite, it is soda. Glassy felspar is a term applied when the crystals have a considerable degree of transparency. Compact felspar is a name of more vague signification. The substance so called appears to contain both potash and soda.
Felspathic. Of or belonging to felspar.
Ferruginous. Any thing containing iron. Etym., ferrum, iron.
Fissile, easily cleft, dividing readily into an indefinite number of parallel laminæ, like slates.
Floetz Rocks. A German term applied to the secondary strata by the geologists of that country, because these rocks were supposed to occur most frequently in flat horizontal beds. Etym., flotz, a layer or stratum.
Flora. The various kinds of trees and plants found in any country constitute the Flora of that country in the language of botanists.
Fluviatile. Belonging to a river. Etym., fluvius, a river.
Foraminifera. A name given by D'Orbigny to a family of microscopic shells. Their different chambers are united by a small perforation or foramen. Recent observation has shown that some at least are not Cephalopoda, as D'Orbigny supposed.
Formation. A group, whether of alluvial deposits, sedimentary strata, or igneous rocks, referred to a common origin or period.
Fossil. All minerals were once called fossils, but geologists now use the word only to express the remains of animals and plants found buried in the earth. Etym., fossilis, any thing that may be dug out of the earth.

Fossiliferous. Containing organic remains.

Galena. A metallic ore, a compound of lead and sulphur. It has often the appearance of highly polished lead. Etym., γαλεω, galeo, to shine.
Garnet. A simple mineral, generally of a deep red color, crystallized; most commonly met with in mica slate, but also in granite and other igneous rocks.
Gasteropods. A division of the Testacea, in which, as in the limpet, the foot is attached to the body. Etym., γαστηρ, gaster, belly, and ποδα, poda, feet.
Gault. A provincial name in the east of England for a series of beds of clay and marl, the geological position of which is between the Upper and Lower Greensand.
Gavial. A kind of crocodile found in India.
Gem, or Gemmule, from the Latin gemma, a bud. The term, applied to zoophytes, means a young animal not confined within an envelope or egg.
Geology, Geognosy. Both mean the same thing; but with an unnecessary degree of refinement in terms, it has been proposed to call our description of the structure of the earth geognosy (Etym., γεα, gea, earth, and γινωσcω, ginosco, to know), and our theoretical speculations as to its formation geology (Etym., γεα, and λογος, logos, a discourse).
Glacier. Vast accumulations of ice and hardened snow in the Alps and other lofty mountains. Etym., glace, French for ice.
Glacis. A term borrowed from the language of fortification, where it means an easy insensible slope or declivity, less steep than a talus, which see.
Gneiss. A stratified primary rock, composed of the same materials as granite, but having usually a larger proportion of mica and a laminated texture. The word is a German miner's term.
Gramineæ. The order of plants to which grasses belong. Etym., gramen, grass.
Granite. An unstratified or igneous rock, generally found inferior to or associated with the oldest of the stratified rocks, and sometimes penetrating them in the form of dikes and veins. It is usually composed of three simple minerals, felspar, quartz, and mica, and derives its name from having a coarse granular structure; granum, Latin for grain. Waterloo bridge, and the paving-stones in the carriage-way of the London streets, afford good examples of the most common varieties of granite.
Greensand. Beds of sand, sandstone, limestone, belonging to the Cretaceous Period. The name is given to these beds because they often, but not always, contain an abundance of green earth or chlorite scattered through the substance of the sandstone, limestone, &c.
Greenstone. A variety of trap, composed of hornblende and felspar.
Greywacké. Grauwacke, a German name, generally adopted by geologists for some of the most ancient fossiliferous strata. The rock is very often of a gray color; hence the name, grau, being German for gray, and wacke, being a provincial miner's term.
Grit. A provincial name for a coarse-grained sandstone.
Gymnospermous. Etym., γυμνος, gymnos, naked, and σπερμα, sperma, a seed. (See Gymnogens.)
Gymnogens. A class of flowering plants, in which the ovules are not inclosed in an ovary. They are also called gymnosperms, the seeds in like manner not being inclosed in a pericarp. It includes all Coniferæ, as pine, fir, juniper, cypress, yew, cedar, &c., and Cycadeæ. All are Dicotyledonous (a few have many cotyledons), and all Exogenous, except Cycas, the growth of which is anomalous. The term is applied in contradistinction to Angiosperms, which see. Etym., γυμνος, naked, and γενεσις, increase.
Gypsum. A mineral composed of lime and sulphuric acid, hence called also sulphate of lime. Plaster and stucco are obtained by exposing gypsum to a strong heat. It is found so abundantly near Paris, that plaster of Paris is a common term in this country for the white powder of which casts are made. The term is used by Pliny for a stone used for the same purposes by the ancients. The derivation is unknown.
Gypseous, of or belonging to gypsum.

Gyrogonites. Bodies found in freshwater deposits, originally supposed to be microscopic shells, but subsequently discovered to be seed-vessels of freshwater plants of the genus Chara. See above p. . Etym., γυρος, gyros, curved, and γονος, gonos, seed, on account of their external structure.

Hemiptera. An order of insects, so called from a peculiarity in their wings, the superior being coriaceous at the base and membranous at the apex, ἡμισυ, hemisu, half, and πτερον, pteron, wing.
Hornblende. A simple mineral of a dark green or black color, which enters largely into the composition of several varieties of the Trap-Rocks.
Hornstone. A siliceous mineral substance, sometimes approaching nearly to flint, or common quartz. It has a conchoidal fracture, and is infusible, which distinguishes it from compact felspar.
Humerus. The bone of the upper arm.
Hydrophytes. Plants which grow in water. Etym., ὑδωρ, hydor, water, and φυτον, phyton, plant.

Hypogene Rocks. Those rocks which are nether-formed, or which have not assumed their present form and structure at the surface, such as granite, gneiss, &c. The term, which includes both the plutonic and metamorphic rocks, is substituted for primary, because some members of both these classes, such as granite and gneiss, are posterior to many secondary or fossiliferous rocks. Etym., ὑπο, hypo, under, and γινομαι, ginomai, to be formed or produced.

Iceberg. Great masses of ice, often the size of hills, which float in the polar and adjacent seas. Etym., ice, and berg, German for hill.
Ichthyosaurus. A gigantic fossil marine reptile, allied in part of its structure to a fish. Etym., ιχθυς, ichthus, a fish, and σαυρα, saura, a lizard.
Igneous Rocks. All rocks, such as lava, trap, and granite, known or supposed to have been melted by volcanic heat.
Incandescent. White hot—having a more intense degree of heat than red heat.
Induction. A consequence, inference, or general principle drawn from a number of particular facts or phenomena. The inductive philosophy, says Mr. Whewell, has been rightly described as a science which ascends from particular facts to general principles, and then descends again from these general principles to particular applications.
Infusory Animalcules. Minute living creatures found in many infusions; and the term infusori has been given to all such animalcules, whether found in infusions or in stagnant water, vinegar, &c.
Inspissated. Thickened. Etym., spissus, thick.
Invertebrated Animals. Animals which are not furnished with a back-bone. For a further explanation, see "Vertebrated Animals."

Isothermal. Such zones or divisions of the land, ocean, or atmosphere, which have an equal degree of mean annual warmth, are said to be isothermal, from ισος, isos, equal, and θερμη, therme, heat.

Joints. Fissures or lines of parting in rocks, often at right angles to the planes of stratification. The partings which divide columnar basalt into prisms are joints.

Jura Limestone. The limestones belonging to the Oolite Group constitute the chief part of the mountains of Jura between France and Switzerland; and hence the geologists of the Continent have given the name to the group.

Keuper. A German name for a member of the Upper New Red Sandstone.

Kimmeridge Clay. A thick bed of clay, constituting a member of the Oolite Group. So called because it is found well developed at Kimmeridge, in the Isle of Purbeck, Dorsetshire.

Lacustrine. Belonging to a lake. Etym., lacus, a lake.
Lamantine. A living species of the herbivorous Cetacea or whale tribe which inhabits the mouth of rivers on the coasts of Africa and South America: the sea-cow.
Lamelliferous. Having a structure consisting of thin plates or leaves like paper. Etym., lamella, the diminutive of lamina, plate, and fero, to bear.
Laminæ. Latin for plates; used in geology for the smaller layers of which a stratum is frequently composed.

Landslip. A portion of land that has slid down in consequence of disturbance by an earthquake, or from being undermined by water washing away the lower beds which supported it.
Lapidification. Lapidifying process. Conversion into stone. Etym., lapis, stone, and fio, to make.
Lapilli. Small volcanic cinders. Lapillus, a little stone.
Lava. The stone which flows in a melted state from a volcano.
Lepidodendron, a genus of fossil plants of the Coal Measures, intermediate in character between the Lycopodiums and coniferous plants.
Leucite. A simple mineral found in volcanic rocks, crystallized, and of a white color. Etym., λευcος, leucos, white.
Lias. A provincial name for an argillaceous limestone, characterized together with its associated beds by peculiar fossils, and forming a particular group of strata, interposed between the Oolite and the New Red Sandstone.
Ligniperdous. A term applied to insects which destroy wood. Etym., lignum, wood, and perdo, to destroy.
Lignite. Wood converted into a kind of coal. Etym., lignum, wood.
Lithodomi. Molluscous animals which form holes in the solid rocks in which they lodge themselves. The holes are not perforated mechanically, but the rock appears to be dissolved. Etym., λιθος, lithos, stone, and δεμο, demo, to build.
Lithogenous Polyps. Animals which form coral.
Lithographic Stone. A slaty compact limestone, of a yellowish color and fine grain, used in lithography, which is the art of drawing upon and printing from stone Etym., λιθος, lithos, stone, and γραφο, grapho, to write.
Lithoidal. Having a stony structure.
Lithological. A term expressing the stony structure or character of a mineral mass. We speak of the lithological character of a stratum as distinguished from its zoological character. Etym., λιθος, lithos, stone, and λογος, logos, discourse.
Lithophagi. Molluscous animals which form holes in solid stones. See "Lithodomi." Etym., λιθος, lithos, stone, and φαγειν, phagein, to eat.
Lithophites. The animals which form Stone-coral.
Littoral. Belonging to the shore. Etym., littus, the shore.
Loam. A mixture of sand and clay.
Lophiodon. A genus of extinct quadrupeds, allied to the tapir, named from eminences on the teeth.
Lycopodiaceæ. Plants of an inferior degree of organization to Coniferæ, some of which they very much resemble in foliage, but all recent species are infinitely smaller. Many of the fossil species are as gigantic as recent Coniferæ. Their mode of reproduction is analogous to that of ferns. In English they are called club-mosses, generally found in mountainous heaths in the north of England.

Lydian Stone. Flinty slate; a kind of quartz or flint, allied to Hornstone, but of a grayish black color.

Macigno. In Italy this term has been applied to a siliceous sandstone sometimes containing calcareous grains, mica, &c.
Madrepore. A genus of corals, but generally applied to all the corals distinguished by superficial star-shaped cavities. There are several fossil species.
Magnesian Limestone. An extensive series of beds, the geological position of which is immediately above the Coal Measures; so called, because the limestone, the principal member of the series, contains much of the earth magnesia as a constituent part.
Mammiferous. Mammifers. Animals which give suck to their young. To this class all the warm-blooded quadrupeds, and the Cetacea, or whales, belong. Etym., mamma, a breast, fero, to bear.
Mammillary. A surface which is studded over with rounded projections. Etym., mammilla, a little breast or pap.
Mammoth. An extinct species of the elephant (E. primigenius), of which the fossil bones are frequently met with in various countries. The name is of Tartar origin, and is used in Siberia for animals that burrow under ground.
Manati. One of the Cetacea, the sea-cow, or lamantine (Trichechus manatus, Lin.)

Marl. A mixture of clay and lime; usually soft, but sometimes hard, in which case it is called indurated marl.
Marsupial Animals. A tribe of quadrupeds having a sack or pouch under the belly, in which they carry their young. The kangaroo is a well-known example. Etym., marsupium, a purse.
Mastodon. A genus of fossil extinct quadrupeds allied to the elephants; so called from the form of the hind teeth or grinders, which have their surface covered with conical mammillary crests. Etym., μαστος, mastos, pap, and οδων, odon, tooth.
Matrix. If a simple mineral or shell, in place of being detached, be still fixed in a portion of rock, it is said to be in its matrix. Matrix, womb.
Mechanical Origin, Rocks of. Rocks composed of sand, pebbles, or fragments, are so called to distinguish them from those of a uniform crystalline texture, which are of chemical origin.
Medusæ. A genus of marine radiated animals, without shells; so called, because their organs of motion spread out like the snaky hair of the fabulous Medusa.
Megalosaurus. A fossil gigantic amphibious animal of the saurian or lizard and crocodile tribe. Etym., μεγαλη, megale, great, and σαυρα, saura, lizard.
Megatherium. A fossil extinct quadruped, resembling a gigantic sloth. Etym., μεγα, mega, great, and θηριον, therion, wild beast.
Melastoma. A genus of Melastomacea, an order of exotic plants of the evergreen tree and shrubby kinds. Etym., μελας, melas, black, and στομα, stoma, mouth; because the fruit of one of these species stains the lips.
Mesotype. A simple mineral, white, and needle-shaped, one of the Zeolite family, frequently met with in the Trap-rocks.
Metamorphic Rocks. A stratified division of hypogene rocks, highly crystalline, such as gneiss and mica-schist, and so named because they have been altered by plutonic action. Etym., μετα, meta, trans, and μορφη, morphe, form.
Mica. A simple mineral, having a shining silvery surface, and capable of being split into very thin elastic leaves or scales. It is often called talc in common life; but mineralogists apply the term talc to a different mineral. The brilliant scales in granite are mica. Etym., mico, to shine.
Mica-slate, Mica-Schist, Micaceous Schistus. One of the metamorphic or crystalline stratified rocks of the hypogene class, which is characterized by being composed of a large proportion of mica united with quartz.
Miocene. A division of tertiary strata intervening between the Eocene and Pliocene formations; so called, because a minority of its fossil shells are referable to living species. Etym., μειων, meion, less, and καινος, kainos, recent.
Molasse. A provincial name for a soft green sandstone, associated with marl and conglomerates, belonging to the Miocene Tertiary Period, extensively developed in the lower country of Switzerland. Etym., French, molle, soft.
Mollusca, Molluscous Animals. Animals, such as shell-fish, which, being devoid of bones, have soft bodies. Etym., mollis, soft.
Monad. The smallest of visible animalcules, spoken of by Buffon and his followers as constituting the elementary molecules of organic beings.
Monitor. An animal of the saurian or lizard tribe, species of which are found in both the fossil and recent state.
Monocotyledonous. A grand division of the vegetable kingdom (including palms, grasses, Lilaceæ, &c.), founded on the plant having only one cotyledon, or seed-lobe. Etym., μονος, monos, single.
Moraine, a Swiss term for the débris of rocks brought into valleys by glaciers. See p. .
Moschus. A quadruped resembling the chamois or mountain goat, from which the perfume musk is obtained.
Mountain Limestone, or Carboniferous Limestone. A series of limestone strata of marine origin, usually forming the lowest member of the Coal Measures.
Moya. A term applied in South America to mud poured out from volcanoes during eruptions.
Multilocular. Many-chambered; a term applied to those shells which, like the nautilus, ammonite, and others, are divided into many compartments. Etym., multus, many, and loculus, a partition.

Muriate of Soda. The scientific name for common culinary salt, because it is composed of muriatic acid and the alkali soda.
Musaceæ. A family of tropical monocotyledonous plants, including the banana and plantains.

Muschelkalk. A limestone, belonging to the Upper New Red Sandstone group. Its position is between the Magnesian Limestone and the Lias. This formation has not yet been found in England, and the German name is adopted by English geologists. The word means shell limestone. Etym., muschel, shell, and kalkstein, limestone.

Naphtha. A very thin, volatile, inflammable, and fluid mineral substance, of which there are springs in many countries, particularly in volcanic districts.
Nenuphar. A yellow water-lily. P. 618.
New Red Sandstone. A formation so named, because it consists chiefly of sandy and argillaceous strata, the predominant color of which is brick-red, but containing portions which are of a greenish-gray. These occur often in spots and stripes, so that the series has sometimes been called the variegated sandstone. This formation is divided into the Upper New Red in which the Muschelkalk is included, and the Lower New Red, of which the Magnesian Limestone is a member.
Nodule. A rounded irregular-shaped lump or mass. Etym., diminutive of nodus, knot.
Normal Groups. Groups of certain rocks taken as a rule or standard. Etym., norma, rule or pattern.
Nucleus. A solid central piece, around which other matter is collected. The word is Latin for kernel.

Nummulites. An extinct genus of the order of molluscous animals, called Cephalopoda, of a thin lenticular shape, internally divided into small chambers. Etym., nummus, Latin for money, and λιθος, lithos, stone, from its resemblance to a coin.

Obsidian. A volcanic product, or species of lava, very like common green bottle glass, which is almost black in large masses, but semi-transparent in thin fragments. Pumice-stone is obsidian in a frothy state; produced, most probably, by water that was contained in or had access to the melted stone, and converted into steam. There are very often portions in masses of solid obsidian, which are partially converted into pumice.
Ochre. A yellow powder, a combination of some earth with oxide of iron.
Ogygian Deluge. A great inundation mentioned in fabulous history, supposed to have taken place in the reign of Ogyges in Attica, whose death is fixed in Blair's Chronological Tables in the year 1764 before Christ. See p. .
Old Red Sandstone. A formation immediately below the Carboniferous Group. The term Devonian has been recently proposed for strata of this age, because in Devonshire they are largely developed, and contain many organic remains.
Oligoclase. A mineral of the felspar family.
Olivine. An olive-colored, semi-transparent, simple mineral, very often occurring in the form of grains and of crystals in basalt and lava.
Oolite, Oolitic. A limestone; so named because it is composed of rounded particles like the roe or eggs of a fish. The name is also applied to a large group of strata, characterized by peculiar fossils, in which limestone of this texture occurs. Etym., ωον, oon, egg, and λιθος, lithos, stone.
Opalized Wood. Wood petrified by siliceous earth, and acquiring a structure similar to the simple mineral called opal.
Ophidious Reptiles. Vertebrated animals, such as snakes and serpents. Etym., οφις, ophis, a serpent.
Organic Remains. The remains of animals and plants (organized bodies) found in a fossil state.
Orthocerata or Ohthoceræ. An extinct genus of the order of molluscous animals, called Cephalopoda, that inhabited a long-chambered conical shell, like a straight horn. Etym., ορθος, orthos, straight, and κερας, ceras, horn.

Osseous Breccia. The cemented mass of fragments of bones of extinct animals found in caverns and fissures. Osseous is a Latin adjective, signifying bony.
Osteology. That division of anatomy which treats of the bones; from οστεον, osteon, bone, and λογος, logos, a discourse.
Outliers. When a portion of a stratum occurs at some distance, detached from the general mass of the formation to which it belongs, some practical mineral surveyors call it an outlier, and the term is adopted in geological language.
Ovate. The shape of an egg. Etym., ovum, egg.
Ovipositing. The laying of eggs.
Oxide. The combination of a metal with oxygen; rust is oxide of iron.

Oxygen. One of the constituent parts of the air of the atmosphere; that part which supports life. For a farther explanation of the word, consult elementary works on chemistry.

Pachydermata. An order of quadrupeds, including the elephant, rhinoceros, horse, pig, &c., distinguished by having thick skins. Etym., παχυς, pachus, thick, and δερμα, derma, skin, or hide.
Pachydermatous. Belonging to Pachydermata.
Palæotherium, Paleothere. A fossil extinct quadruped, belonging to the order Pachydermata, resembling a pig, or tapir, but of great size. Etym., παλαιος, palaios, ancient, and θηριον, therion, wild beast.
Paleontology. The science which treats of fossil remains, both animal and vegetable. Etym., παλαιος, palaios, ancient, οντα, onta, beings, and λογος, logos, a discourse.
Pelagian, Pelagic. Belonging to the deep sea. Etym., pelagus, sea.
Peperino. An Italian name for a particular kind of volcanic rock, formed like tuff, by the cementing together of volcanic sand, cinders, or scoriæ, &c.
Petroleum. A liquid mineral pitch, so called because it is seen to ooze like oil out of the rock. Etym., petra, rock, and oleum, oil.
Phænogamous or Phanerogamic Plants. A name given by Linnæus to those plants in which the reproductive organs are apparent. Etym., φανερος, phaneros, evident, or φαινω, phaino, to show, and γαμος, gamos, marriage.
Phlegræan Fields. Campi Phlegræi, or "the Burnt Fields." The country around Naples, so named by the Greeks, from the traces of igneous action everywhere visible.
Phonolite. See "Clinkstone."
Phryganea. A genus of four-winged insects, the larvæ of which, called caddis-worms, are used by anglers as a bait.
Physics. The department of science which treats of the properties of natural bodies, laws of motion, &c.; sometimes called natural philosophy and mechanical philosophy. Etym., φυσις, physis, nature.
Phytology, Phytological. The department of science which relates to plants—synonymous with, botany and botanical. Etym., φυτον, phyton, plant, and λογος, logos, discourse.
Phytophagous. Plant-eating. Etym., φυτον, phyton, plant, and φαγειν, phagein, to eat.
Pisolite. A stone possessing a structure like an agglutination of peas. Etym., πισον, pison, pea, and λιθος, lithos, stone.
Pistia. P. 618. The plant mentioned by Malte-Brun is probably the Pistia Stratiotes, a floating plant, related to English duckweed, but very much larger.
Pit Coal. Ordinary coal; called so, because it is obtained by sinking pits in the ground.
Pitchstone. A rock of a uniform texture, belonging to the unstratified and volcanic classes, which has an unctuous appearance like indurated pitch.
Plastic Clay. One of the beds of the Eocene Tertiary Period; so called, because it is used for making pottery. The formation to which this name is applied is a series of beds chiefly sands, with which the clay is associated. Etym., πλασσω, plasso, to form or fashion.
Plesiosaurus. A fossil extinct amphibious animal, resembling the saurian, or lizard and crocodile tribe. Etym., πλησιον, plesion, near to, and σαυρα, saura, a lizard.

Pliocene, Older and Newer. Two divisions of the Tertiary Period which are the most modern, and of which the largest part of the fossil shells are of recent species. Etym., πλειων, pleion, more, and καινος, kainos, recent.
Plutonic Action. The influence of volcanic heat and other subterranean causes under pressure.
Plutonic Rocks. Granite, porphyry, and other igneous rocks supposed to have consolidated from a melted state at a great depth from the surface.
Poliparia. Corals. A numerous class of invertehrated animals, belonging to the great division called Radiata.
Porphyry. An unstratified or igneous rock. The term is as old as the time of Pliny, and was applied to a red rock with small, angular, white bodies diffused through it, which are crystallized felspar, brought from Egypt. The term is hence applied to every species of unstratifled rock in which detached crystals or felspar or some other mineral are diffused through a base of other mineral composition. Etym., πορφυρα, porphyra, purple.
Portland Limestone, Portland Beds. A series of limestone strata, belonging to the upper part of the Oolite Group, found chiefly in England in the Island of Portland on the coast of Dorsetshire. The great supply of the building-stone used in London is from these quarries.
Pozzuolana. Volcanic ashes, largely used as mortar for buildings, similar in nature to what is called in this country Roman cement. It gets its name from Puzzuoli, a town in the Bay of Naples, from which it is shipped in large quantities to all parts of the Mediterranean.
Precipitate. Substances which, having been dissolved in a fluid, are separated from it by combining chemically and forming a solid, which falls to the bottom of the fluid. This process is the opposite to that of chemical solution.
Producta. An extinct genus of fossil bivalve shells occurring only in the older secondary rocks. It is closely allied to the living genus Terebratula.
Pterodactyl. A flying reptile: species of this genus have been found in the Oolite and Muschelkalk. Some of the finger-joints are lengthened, so as to serve as the expansors of a membranous wing. Hence the name wing-fingered. Etym., πτερον, pteron, a wing, and δακτυλος, dactylos, a finger.
Pubescence. The soft hairy down on insects. Etym., pubesco, the first growth of the beard.
Puddingstone. See "Conglomerate."
Pumice. A light spongy lava, chiefly felspathic, of a white color, produced by gases or watery vapor getting access to the particular kind of glassy lava called obsidian, when in a state of fusion; it may be called the froth of melted volcanic glass. The word comes from the Latin name of the stone, pumex.
Purbeck Limestone, Purbeck Beds. Limestone strata, belonging to the Wealden Group, which intervenes between the Greensand and the Oolite.
Pyrites. (Iron.) A compound of sulphur and iron, found usually in yellow shining-crystals like brass, and in almost every rock, stratified and unstratifled. The shining metallic bodies so often seen in common roofing slate are a familiar example of the mineral. The word is Greek, and comes from πυρ, pyr, fire; because tinder particular circumstances, the stone produces spontaneous heat, and even inflammation.

Pyrometer. An instrument for measuring intense degrees of heat.

Quadrumana. The order of mammiferous animals to which apes belong. Etym., quadrus, a derivative of the Latin word for the number four, and manus, hand, the four feet of those animals being in some degree usable as hands.
Qua-qua-versal Dip. The dip of beds to all points of the compass around a centre, as in the case of beds of lava round the crater of a volcano. Etym., quâ-quâ-versum, on every side.
Quartz. A German provincial term, universally adopted in scientific language for a simple mineral composed of pure silex, or earth of flints: rock-crystal is an example.

Quartzite or Quartz Rock. An aggregate of grains of quartz, sometimes passing into compact quartz.

Red Marl. A term often applied to the New Red Sandstone.
Reticulate. A structure of cross lines, like a net, is said to be reticulated, from rete, a net.
Rock Salt. Common culinary salt, or muriate of soda, found in vast solid masses or beds, in different formations, extensively in the New Red Sandstone formation, as in Cheshire; and it is then called rock-salt.
Rubble. A term applied by quarry-men to the upper fragmentary and decomposed portion of a mass of stone.

Ruminantia. Animals which ruminate or chew the cud, such as the ox, deer, &c. Etym., the Latin verb rumino, meaning the same thing.

Saccharoid, Saccharine. When a stone has a texture resembling that of loaf-sugar. Etym., σακχαρ, sacchar, sugar, and ειδος, eidos, form.
Salient Angle. In a zigzag line a a are the salient angles, b b the re-entering angles. Etym., salire, to leap or bound forward.
Salt Springs. Springs of water containing a large quantity of common salt. They are very abundant in Cheshire and Worcestershire, and culinary salt is obtained from them by mere evaporation.
Sandstone. Any stone which is composed of an agglutination of grains of sand, whether calcareous, siliceous, or of any other mineral nature.
Saurian. Any animal belonging to the lizard tribe. Etym., σαυρα, saura, a lizard.
Saxicavous. Hollowing out stone.
Schist is often used as synonymous with slate; but it may be very useful to distinguish between a schistose and a slaty structure. The hypogene or primary schists, as they are termed, such as gneiss, mica-schist, and others, cannot be split into an indefinite number of parallel laminæ like rocks which have a true slaty cleavage. The uneven schistose layers of mica-schist and gneiss are probably layers of deposition, which have assumed a crystalline texture. See "Cleavage." Etym., schistus, adj. Latin, that which may be split.
Schistose Rocks. See "Schist."
Scoriæ. Volcanic cinders. The word is Latin for cinders.
Seams. Thin layers which separate two strata of greater magnitude.
Secondary Strata. An extensive series of the stratified rocks which compose the crust of the globe, with certain characters in common, which distinguish them from another series below them called primary, and from a third series above them called tertiary.
Secular Refrigeration. The periodical cooling and consolidation of the globe from a supposed original state of fluidity from heat. Sæculum, age or period.
Sedimentary Rocks are those which have been formed by their materials having been thrown down from a state of suspension or solution in water.
Selenite. Crystallized gypsum, or sulphate of lime—a simple mineral.
Septaria. Flattened balls of stone, generally a kind of iron-stone, which, on being split, are seen to be separated in their interior into irregular masses. Etym., septa, inclosures.
Serpentine. A rock usually containing much magnesian earth, for the most part unstratified, but sometimes appearing to be an altered or metamorphic stratified rock. Its name is derived from frequently presenting contrasts of color, like the skin of some serpents.
Shale. A provincial term, adopted by geologists, to express an indurated slaty clay. Etym., German schalen, to peel, to split.
Shell Marl. A deposit of clay, peat, and other substances mixed with shells, which collects at the bottom of lakes.
Shingle. The loose and completely water-worn gravel on the sea-shore.
Silex. The name of one of the pure earths, being the Latin word for flint, which is wholly composed of that earth. French geologists have applied it as a generic name for all minerals composed entirely of that earth, of which there are many of different external forms.
Silica. One of the pure earths. Etym., silex, flint, because found in that mineral.
Silicate. A chemical compound of silica and another substance, such as silicate of iron. Consult elementary works on chemistry.
Siliceous. Of or belonging to the earth of flint. Etym., silex, which see. A siliceous rock is one mainly composed of silex.
Silicified. Any substance that is petrified or mineralized by siliceous earth.
Silt. The more comminuted sand, clay, and earth, which is transported by running water. It is often accumulated by currents in banks. Thus the mouth of a river is silted up when its entrance into the sea is impeded by such accumulation of loose materials.
Simple Mineral. Individual mineral substances, as distinguished from rocks, which last are usually an aggregation of simple minerals. They are not simple in regard to their nature; for when subjected to chemical analysis, they are found to consist of a variety of different substances. Pyrites is a simple mineral in the sense we use the term, but it is a chemical compound of sulphur and iron.
Sinter, Calcareous or Siliceous. A German name for a rock precipitated from mineral waters. Etym., sintern, to drop.
Slate. See "Cleavage" and "Schist."

Solfatara. A volcanic vent from which sulphur, sulphureous, watery, and acid vapors and gases are emitted.
Sporules. The reproductory corpuscula (minute bodies) of cryptogamic plants. Etym., σπορα, spora, a seed.
Stalactite. When water holding lime in solution deposits it as it drops from the roof of a cavern, long rods of stone hang down like icicles, and these are called stalactites. Etym., σταλαζω, stalazo, to drop.
Stalagmite. When water holding lime in solution drops on the floor of a cavern, the water evaporating leaves a crust composed of layers of limestone: such a crust is called stalagmite, from σταλαγμα, stalagma, a drop, in opposition to stalactite, which see.
Statical Figure. The figure which results from the equilibrium of forces. From στατος, statos, stable, or standing still.
Sternum. The breast-bone, or the flat bone occupying the front of the chest.
Stilbite. A crystallized simple mineral, usually white, one of the Zeolite family, frequently included in the mass of the Trap-rocks.
Stratified. Rocks arranged in the form of strata, which see.
Stratification. An arrangement of rocks in strata, which see.
Strata, Stratum. The term stratum, derived from the Latin verb struo, to strew or lay out, means a bed or mass of matter spread out over a certain surface by the action of water, or in some cases by wind. The deposition of successive layers of sand and gravel in the bed of a river, or in a canal, affords a perfect illustration both of the form and origin of stratification. A large portion of the masses constituting the earth's crust are thus stratified, the successive strata of a given rock preserving a general parallelism to each other; but the planes of stratification not being perfectly parallel throughout a great extent like the planes of cleavage, which see.
Strike. The direction or line of bearing of strata, which is always at right angles to their prevailing dip.
Stufas. Jets of steam issuing from fissures in volcanic regions at a temperature often above the boiling point.
Subapennines. Low hills which skirt or lie at the foot of the great chain of the Apennines in Italy. The term. Subapennine is applied geologically to a series of strata of the Older Pliocene Period.

Syenite. A kind of granite; so called, because it was brought from Syene in Egypt.

Talus. When fragments are broken off by the action of the weather from the face of a steep rock, as they accumulate at its foot, they form a sloping heap, called a talus. The term is borrowed from the language of fortification, where talus means the outside of a wall of which the thickness is diminished by degrees, as it rises in height, to make it the firmer.
Tarsi. The feet in insects, which are articulated, and formed of five or a less number of joints.
Tertiary Strata. A series of sedimentary rocks, with characters which distinguish them from two other great series of strata—the secondary and primary—which lie beneath them.
Testacea. Molluscous animals, having a shelly covering. Etym., testa, a shell, such as snails, whelks, oysters, &c.
Thallogens. A class of flowerless plants including all those that have no defined axis, stem, or leaves; as Lichens, Seaweeds, and Fungi. Etym., θαλλος, thallos, a branch, and γενεσις, genesis, increase.
Thermal. Hot. Etym., θερμος, thermos, hot.
Thermo-electricity. Electricity developed by heat.
Thin Out. When a stratum, in the course of its prolongation in any direction, becomes gradually less in thickness, the two surfaces approach nearer and nearer; and when at last they meet, the stratum is said to thin out or disappear.
Trachyte. A variety of lava essentially composed of glassy felspar, and frequently having detached crystals of felspar in the base or body of the stone, giving it the structure of porphyry. It sometimes contains hornblende and augite; and when these last predominate, the trachyte passes into the varieties of trap, called Greenstone, Basalt, Dolorite, &c. The term is derived from τραχυς, trachus, rough, because the rock has a peculiar rough feel.
Trap and Trappean Rocks. Volcanic rocks composed of felspar, augite, and hornblende. The various proportions and state of aggregation of these simple minerals, and differences in external forms, give rise to varieties, which have received distinct appellations, such as Basalt, Amygdaloid, Dolorite, Greenstone, and others. The term is derived from trappa, a Swedish word for stair, because the rocks of this class sometimes occur in large tabular masses, rising one above another like steps.
Travertin. A white concretionary limestone, usually hard and semi-crystalline, deposited from the water of springs holding lime in solution.—Etym. This stone was called by the ancients Lapis Tiburtinus, the stone being formed in great quantity by the river Anio, at Tibur, near Rome. Some suppose travertin to be an abbreviation of trasterverino from transtiburtinus.
Tripoli. The name of a powder used for polishing metals and stones, first imported from Tripoli, which, as well as a certain kind of siliceous stone of the same name, has been lately found to be composed of the flinty cases of Infusoria.
Trophi, of Insects. Organs which form the mouth, consisting of an upper and under lip, and comprising the parts called mandibles, maxillæ, and palpi.
Tufa, Calcareous. A porous rock deposited by calcareous waters on their exposure to the air, and usually containing portions of plants and other organic substances incrusted with carbonate of lime. The more solid form of the same deposit is called "travertin," into which it passes.
Tufa, Volcanic. See "Tuff."
Tufaceous. A rock with the texture of tuff, or tufa, which see.
Tuff, or Tufa Volcanic. An Italian name for a variety of volcanic rock of an earthy texture, seldom very compact, and composed of an agglutination of fragments of scoriæ and loose materials ejected from a volcano.
Turbinated. Shells which have a spiral or screw-form structure. Etym., turbinatus, made like a top.

Turrilite. An extinct genus of chambered shells, allied to the Ammonites, having the siphuncle near the dorsal margin.

Unconformable. See "Conformable."

Unoxidized, Unoxidated. Not combined with oxygen.

Veins, Mineral. Cracks in rocks filled up by substances different from the rock, which may either be earthy or metallic. Veins are sometimes many yards wide; and they ramify or branch off into innumerable smaller parts, often as slender as threads, like the veins in an animal, hence their name.
Vertebrated Animals. A great division of the animal kingdom, including all those which are furnished with a back-bone, as the mammalia, birds, reptiles, and fishes. The separate joints of the back-bone are called vertebræ, from the Latin verb verto, to turn.
Vesicle. A small, circular, inclosed space, like a little bladder. Etym., diminutive of vesica, Latin for a bladder.
Vitrification. The conversion of a body into glass by heat.
Volcanic Bombs. Volcanoes throw out sometimes detached masses of melted lava, which, as they fall, assume rounded forms (like bomb-shells), and are often elongated into a pear-shape.

Volcanic Foci. The subterranean centres of action in volcanoes, where the heat is supposed to be in the highest degree of energy.

Wacke. A rock nearly allied to basalt, of which it may be regarded as a soft and earthy variety.

Warp. The deposit of muddy waters, artificially introduced into low lands. See p. .

Zeolite. A family of simple minerals, including stilbite, mesotype, analcime, and some others, usually found in the trap or volcanic rocks. Some of the most common varieties swell or boil up when exposed to the blow-pipe, and hence the name of ζεο, zeô, to boil, and λιθος, lithos, stone.
Zoophites. Corals, sponges, and other aquatic animals allied to them; so called because, while they are the habitation of animals, they are fixed to the ground, and have the form of plants. Etym., ζωον, zoon, animal, and φυτον, phyton, plant.