Section II.
Further strictures on the ancient state of this country, and on a wonderful change it appears to have undergone, at a very remote and unknown period; from De Serra’s account of a submarine Forest on the coast of Lincolnshire.
Some very remote ages ago, the land, it seems, extended much further out on the Lincolnshire coast than it does at present; and it appears that whole forests once existed in places now wholly occupied by the ocean; which must tend to corroborate what has been already suggested, that the whole face of the fens was originally a forest. A remarkable Paper, giving an account of a Submarine Forest on the said coast, appeared in the Philosophical Transactions for 1799. Part I. written by Joseph Correa De Serra L.L.D. F.R.S. and A.S. in which the Author informs us of a report in Lincolnshire, that a large extent of islets of moor, situated along the coast, and visible only in the lowest ebbs of the year, was chiefly composed of decayed trees. That report induced him to take a journey thither for the purpose of inspecting so singular a curiosity. Those islets, he observes, are marked in Mitchell’s Chart of that coast by the name of Clay huts; and the Village of Huttoft, opposite to which they principally lie, he supposes to have derived its name from them.
“In the Month of September 1796, (says he) I went to Sutton, on the coast of Lincolnshire, in the company of the right honourable the President of the Royal Society, in order to examine their nature and extent. The 19th of the month being the day after the equinoctial full moon, when the lowest ebbs were to be expected, we went in a boat, about half past twelve at noon, and soon set foot on one of the largest islands then appearing. Its exposed surface was about 30 yards long, and 25 wide when the tide was at the lowest. A great number of smaller islets were visible around us to the eastward and southward; and the fishermen whose authority in this point is very competent, say that similar moors are to be found along the whole coast from Skegness to Grimsby, particularly off Addlethorpe and Mablethorpe. The channels dividing the islets were, at the time we saw them, wide and of various depths; the islets themselves ranging generally from east to west in their largest dimensions.
“We visited them again in the ebbs of the 20th and 21st.; and though it did not generally ebb so far as we expected, we could notwithstanding ascertain that they consisted almost entirely of roots, trunks, branches, and leaves of trees and shrubs, intermixed with some leaves of aquatic plants. The remains of some of these trees were still standing on their roots, while the trunks of the greater part lay scattered on the ground in every possible direction. The barks of trees and roots appeared generally as fresh as when they were growing; in that of the branches particularly, of which a great quantity was found, even the thin silver membranes of outer skin were discernible. The timber of all kinds on the contrary, was decomposed, and soft in the greatest part of the trees: in some, however, it was firm, especially in the roots. The people of the country have often found among them very sound pieces of timber, fit to be employed for several economical purposes. The sorts of wood which are still distinguishable are, birch, fir, and oak. Other woods evidently exist in these islets, of some of which we found the leaves in the soil; but our present knowledge of the comparative anatomy of timber is not so far advanced as to afford us the means of pronouncing with confidence respecting their species. In general the trunks, branches, and roots of the decayed trees were considerably flattened, which is a phenomenon observed in the Surtarbrand, or fossil wood of Iceland, and which Scheuchzer remarked also in the fossil wood found in the neighbourhood of the lake Thun in Switzerland.
“The soil to which the trees are fixed, and in which they grew, is a soft greasy clay; but for many inches above the surface, the soil is composed of rotten leaves, scarcely distinguishable to the eye, many of which may be separated by putting the soil in water and dexterously and patiently using the Spatula, or blunt knife. By this method I obtained some imperfect leaves of the Ilexaquifolium, which are now in the Herbarium of the right honourable Sir Joseph Banks; and some other leaves, though less perfect, seem to belong to some species of willow. In this stratum of rotten leaves we could also distinguish some roots of Arundo Phragmites.
“These islets, according to the most accurate information, extend at least twelve miles in length, and about a mile in breadth, opposite to Sutton shore. The water without them toward the sea, generally deepens suddenly, so as to form a steep bank. The channels between the several islets, when the islets are dry, in the lowest ebbs of the year, are from four to twelve feet deep: their bottoms are clay or sand, and their direction is generally from east to west.
“A well, dug at Sutton by Joshua Searby, shews that a moor of the same nature is found under ground in that part of the country, at the depth of sixteen feet, consequently very nearly on the same level with that which constitutes the islets. The disposition of the strata was found to be nearly as follows: clay sixteen feet; moor, similar to that of the islets, three or four ditto; soft moor, like the scourings of a ditch bottom, mixed with shells and silt, twenty feet; marly clay, one foot; chalky rock, from one to two feet; clay, thirty-one yards; gravel and water; the water has a chalybeate taste. In order to ascertain the course of this subterraneous stratum of decayed vegetables, Sir Joseph Banks directed a boring to be made in the fields belonging to the royal Society in the parish of Mablethorpe. Moor of a similar nature to that of Searby’s well, and the islets, was found very nearly on the same level, about four feet thick, and under a soft clay.
“The whole appearance of the rotten vegetables we observed, perfectly resembles, according to the remark of Sir Joseph Banks, the moor which, in Blakeney Fen, and in other parts of the East Fen in Lincolnshire, is thrown up in the making of banks; barks like those of the birch-tree being there also abundantly found. The moor extends over all the Lincolnshire fens, and has been traced as far as Peterborough, more than sixty miles to the south of Sutton. On the north side, according to the fishermen, the moory islets extend as far as Grimsby, situated on the south side of the Humber: and it is a remarkable circumstance, that in the large tracts of low land which lie on the south banks of that river, a little above its mouth, there is a subterraneous stratum of decayed trees and shrubs, exactly like those we have observed at Sutton; particularly at Axolme isle, a tract of ten miles in length by five in breadth; and at Hatfield chace, which comprehends 180,000 acres. Dugdale had long ago made this observation in the first of these places; and Dela Prime in the second. The roots are there likewise standing in the places where they grew: the trunks lie prostrate. The woods are of the same species as at Sutton. Roots of aquatic plants and reeds are likewise mixed with them; and they are covered by a stratum of some yards of soil, the thickness of which, though not ascertained with exactness by the abovementioned observers, we may easily conceive to correspond with what covers the stratum of decayed wood at Sutton, by the circumstances of the roots being (according to Mr. Richardson’s observations) only visible when the water is low, where a channel was cut which has left them uncovered.
“Little doubt can be entertained of the moory islets of Sutton being a part of this extensive and subterraneous stratum, which, by some inroad of the sea, has there been stripped of its covering of soil. The identity of the levels; that of the species of trees; the roots of these affixed in both to the soil where they grew; and above all, the flattened shape of the trunks, branches, and roots, found in the islets (which can only be accounted for by the heavy pressure of a superinduced stratum) are sufficient reasons for this opinion.”
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. [49]