Section III

Further observations from the same Paper—Epoch of the destruction of the said Forest—Agency by which it was effected, &c.—Similar appearances eastward along the Norfolk coast.

“Such a wide-spread assemblage of vegetable ruins, lying almost in the same level, and that level generally under the common mark of low water, must naturally strike the observer, and give birth to the following questions: 1. What is the epoch of this destruction? 2. By what agency was it effected?

“In answer to these questions I will venture to submit the following reflections: The fossil remains of vegetables hitherto dug up in so many parts of the globe, are, on a close inspection, found to belong to two different states of our planet. The parts of vegetables and their impressions, found in mountains, of a colaceous and schistous, or even sometimes of a calcareous nature, are chiefly of plants now existing between the tropics, which would neither have grown in the latitudes in which they are dug up, nor have been carried and deposited there by any of the acting forces under the present constitution of nature. The formation indeed of the very mountains in which they are buried, and the nature and position of the materials which compose them, are such as we cannot account for by any actions and re-actions which in the actual state of things take place on the surface of the earth. We must necessarily recur to that period in the history of our planet, when the surface of the ocean was at least so much above its present level as to cover even the summits of those secondary mountains which contain the remains of tropical plants. The changes which these vegetables have suffered in their substance is almost total; they commonly retain only the external configuration of what they were. Such is the state in which they are found in England by Lhwyd; in France by Jussicu; and in the Netherlands by Burtin; not to mention instances in more distant countries. Some of the impressions or remains of plants found in soils of this nature which were, by the more ancient and enlightened oryctologists, supposed to belong to plants actually growing in temperate and cold climates, seem, on accurate investigation, to have been part of exotic vegetables. In fact, whether we suppose them to have grown near the spot where they are found, or to have been carried thither from different parts by the force of an impelling flood, it is equally difficult to conceive how organized beings, which, in order to live, require such a vast difference in temperature and seasons, could live on the same spot, or how their remains could (from climates so widely distant) be brought together in the place by one common dislocating cause. To this ancient order of fossil vegetables belong whatever retains a vegetable shape found in or near coalmines, and (to judge from the places where they have been found) the greater part of the agatized woods. But from the species and state of the trees which are the subject of this memoir, and from the situation and nature of the soil in which they are found, it seems very clear that they do not belong to the primeval order of vegetable ruins.

“The second order of fossil vegetables comprehend those which are found in the strata of clay or sand; materials which are the result of slow depositions of the sea and of rivers, agents still at work under the present constitution of our planet. These vegetable remains are found in such flat countries as may be considered to be a new formation. The vegetable organization still subsists, at least in part; and their vegetable substance has suffered a change only in colour, smell, or consistence; alterations which are produced by the development of their oily and bitumenous parts, or by their natural progress towards rottenness. Such are the fossil vegetables found in Cornwall by Borlase; in Essex, by Derham; in Yorkshire by Dela Prime and Richardson; and in foreign countries by other naturalists. These vegetables are found at different depths; some of them much below the present level of the sea, but in clayey and sandy strata (evidently belonging to modern formation); and have, no doubt, been carried from their original place and deposited there by the force of great rivers or currents, as it has been observed with respect to the Mississippi. In many instances, however, these trees and shrubs are found standing on their roots, and generally in low or marshy places above, or very little below the level of the sea.

“To this last description of fossil vegetables the decayed trees here described certainly belong. They have not been transported by currents or rivers; but though standing in their native soil, we cannot suppose the level in which they are found to be the same as that in which they grew. It would be impossible for any of these trees or shrubs to vegetate so near the sea, and below the common level of its water. The waves would cover such tracts of land, and hinder any vegetation. We cannot conceive that the surface of the ocean has ever been any lower than it is now; on the contrary we are led, by numberless phenomena to believe that the level of the water in our globe is now below what it was in former periods. We must therefore conclude, that the forest here described grew in a level high enough to permit its vegetation; and that the force (whatever it was) which destroyed it, lowered the level of the ground where it stood.

“There is a force of subsidence (particularly in soft ground) which being a natural consequence of gravity, slowly, though imperceptibly operating, has its action sometimes quickened and rendered sudden by extraneous causes; for instance, by earthquakes. The slow effects of this force of subsidence have been accurately remarked in many places: examples also of its sudden action are recorded in almost every history of great earthquakes.—In England, Borlase has given in the Philosophical Transactions a curious observation of a subsidence of at least sixteen feet in the ground between Sampson and Trecaw islands in Scilly. The soft and low grounds between the towns of Thorne and Gowle in Yorkshire, a space of many miles, has so much subsided in latter times, that some old men of Thorne affirmed, “that whereas they could before see little of the Steeples (of Gowle) they now see the church yard wall.” The instances of similar subsidence which might be mentioned, are innumerable.

“The force of subsidence, suddenly acting by means of some earthquake, seems to me the most probable cause to which the usual submarine situation of the forest we are speaking of may be ascribed. It affords a simple easy explanation of the matter; its probability is supported by numberless instances of similar events; and it is not liable to the strong objections which exist against the hypothesis of the ultimate depression and elevation of the level of the ocean; an opinion which, to be credible, requires the support of a great number of proofs less equivocal than those which have hitherto been urged in its favour, even by the genius of Lavoisier.

“The stratum of soil, sixteen feet thick, placed above the decayed trees, seems to remove the epoch of their sinking and destruction far beyond the reach of any historical knowledge. In Cæsar’s time the level of the north sea appears to have been the same as in our days. He mentions the separation of the Wahal branch of the Rhine, and its junction with the Meuse; noticing the then existing distance from that junction to the sea, which agrees according to D’Anville’s inquiries, with the actual distance. Some of the Roman roads, constructed according to the order of Augustus, under Agrippa’s administration, leading to the maritime towns of Belgium, still exist, and reach the present shore. The description which Roman authors have given of the coast, ports, and mouths of rivers, on both sides of the North sea, agree in general with their present state; except in places ravaged by the inroads of this sea, more apt from its force to destroy the surrounding countries than to increase them.

“An exact resemblance exists between maritime Flanders and the opposite coast of England, both in point of elevation above the sea, and of the internal structure and arrangement of the soils. On both sides strata of clay, silt, and sand, (often mixed with decayed vegetables) are found near the surface; and in both, these superior materials cover a very deep stratum of blueish or dark coloured clay, unmixed with extraneous bodies. On both sides they are the lowermost part of the soil, existing between two ridges of high lands, on their respective sides of the same narrow sea. These two countries are certainly coeval; and whatever proves that maritime Flanders has been for many ages out of the sea, must, in my opinion, prove also that the forest we are speaking of was long before that time destroyed and buried under a stratum of soil. Now it seems proved from historical records, carefully collected by several learned members of the Brussels Academy, that no material change has happened in the lowermost part of maritime Flanders during the period of the last two thousand years.

“I am therefore inclined to suppose the original catastrophe which buried this forest to be of very ancient date; but I suspect the inroad of the sea which uncovered the decayed trees of the islands of Sutton, to be comparatively recent. The state of the leaves and of the timber, and also the tradition of the neighbouring people concur to strengthen this suspicion.”

The reader, it is hoped, will excuse, and even approve the length of this curious extract, as it seems so well calculated to account for and elucidate divers striking phenomena in the natural history of the Fens.

Here it may not be improper further to observe, that the forest above described seems to have extended from the coast of Lincolnshire a considerable way along the Norfolk coast; as there is on the shore, near Thornham in that county, at low water, the appearance of a large forest having been, at some period, interred and swallowed up by the waves. Stools of numerous large timber trees, and many trunks, are to be seen, but so rotten, that they may be penetrated by a spade. These lie in a black mass of vegetable fibres, consisting of decayed branches, leaves, rushes, flags, &c. The extent of this once sylvan tract [on the Norfolk coast] must have been great, from what is discoverable; and at high water, now covered by the tides, is in one spot from five to six-hundred acres. No hint of the manner, or the time, in which this submersion happened, can be traced. Nothing like a bog is near, and the whole beach besides is composed of a fine ooze, or marine clay.