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CHAPTER XVI. CONTRIBUTIONS ON ENGINEERING AND SCIENTIFIC SUBJECTS.
    Contributions to Encyclop?dia Britannica and Edinburgh Encyclop?dia—The alveus or bed of the German Ocean—Sectio planography—Wasting effects of the sea at the Mersey and Dee—Density of fresh and salt water—The Hydrophore.

We have seen that Mr. Stevenson’s college education was mainly, if not altogether, due to his own thirst for knowledge, and his education being voluntarily undertaken, could hardly fail to issue in good results. That his early studies were of incalculable value to him no one can doubt; and his own conviction of this may explain the solicitude with which, in after life, he impressed on his sons the extreme importance of being properly grounded in every branch of study, scientific and practical, which a well trained engineer has to call to his aid in the practice of his profession.

Fortified by this valuable training, Mr. Stevenson had also that unselfish love of his profession which alone can move a man to give the results of his experience freely to others, and this he did to the Edinburgh Encyclop?dia and the Encyclop?dia Britannica, in articles on “Roads,” “Lighthouses,” “Railways,” “Dredging,” “Blasting,” and other engineering subjects.

204 But he did not confine his literary labours to matters purely professional. His love for nature in all its aspects led him also to make communications to the Scientific Journals of the day on subjects of more general interest. Of these his papers “On the Alveus or Bed of the German Ocean,” in which by an investigation of many evidences he is led to the conclusion that the sea is gradually encroaching on the land, may be quoted as an example.

Mr. Stevenson’s first communication on this subject was published in 1816, in vol. ii. of the Wernerian Transactions, in which he gives examples, from actual observation, of the wasting effects of the sea on various parts of the coasts of the British Isles. His second communication was made to the Wernerian Society in March 1820, and published in the Edinburgh Philosophical Journal of that year.

In the fifth edition of Baron Cuvier’s “Essay on the Theory of the Earth,” reference is made to Mr. Stevenson’s theory. His papers are several times quoted in Lyell’s Principles of Geology, and the General Committee of the British Association at York in 1834 passed a resolution, “that Mr. Stevenson be requested to report to the next meeting upon the waste and extension of the land on the east coast of Britain, and upon the general question of the permanence of the level of the sea and land, and that individuals who may be able to supply information upon the subject be requested to correspond with him.”

Without discussing in how far Mr. Stevenson’s theory may be sound (for on such questions it is notorious that205 the views of geologists do not always coincide), it cannot be denied that his mode of dealing with the subject is original and interesting, and as the papers are not now accessible to the general reader, it may be excusable to give one of them in extenso. I also notice another feature which gives interest to the subject. In his illustrations he adopted a mode of representation which was peculiarly suitable for the object in view. It will be seen from Plate XII. that the sections are laid down on what is now known by engineers as sectio planography, which it is believed was used for the first time in illustrating this paper.
“On the Bed of the German Ocean, or North Sea. (Read before the Wernerian Natural History Society, 25th March 1820.)”

“The efforts of man in exploring the more occult processes of nature are necessarily much circumscribed, especially when his attempts are directed to the investigation of regions which his senses cannot penetrate. It has accordingly been with the utmost difficulty that his exertions have been rendered in any degree successful in prying into the bowels of the earth, or in his endeavours to ascend to the a?rial regions. In proof of this, the limited excavations even of the most extensive mining works, have required the lapse of ages, and the powerful stimulus of commercial enterprise, for their accomplishment. From these the philosopher has not hitherto derived much light, to enable him to compare the theories which have been assigned by geologists to account for the various and206 discordant appearances of the structure of the globe. It has also been with much difficulty, and at no small personal hazard, that the philosophical inquirer has ventured to climb the highest mountains, to examine into the phenomena of the atmosphere. The balloon has indeed enabled us to attain still higher points of elevation; but as yet we do not seem to have made proportional progress in knowledge. In all such attempts to ascend the greatest heights or penetrate the deepest excavations, we still breathe in our own element, though under different modifications. If, however, we would explore the depths of the Ocean, we immediately encounter an element to which the organisation of our lungs is not at all adapted; the density of air, compared with water on a level with the surface of the sea, being in the ratio of one to about 850; and our difficulties must consequently increase in a very rapid proportion. Here therefore we are unavoidably left to conjecture on many points of our inquiries regarding this highly interesting subject. Even the ingenious contrivance of the diving bell contributes but little towards our investigations for ascertaining the nature of the bottom of the sea, at least to any considerable depth, on account of the difficulty of its application in situations exposed to stormy weather, and also of the increasing ratio of the pressure of the fluid as we descend. This curious machine, it is believed, was invented and employed, about the year 1720, by a Captain Rowe for raising the wreck of ships upon the coast of Scotland; and in the year 1778, the active mind of Smeaton first applied it to the operations of the engineer.

PLATE XII.

CHART
of the
NORTH SEA OR GERMAN OCEAN
with SECTIONS of the
DEPTHS of WATER
Illustrative of Observations
by
ROBERT STEVENSON
Civil Engineer
1820.

W. & A. K. Johnston, Edinburgh.

207 “Our knowledge of the bottom of the ocean, therefore, remains still very imperfect, and, with little exception, the simple apparatus of the mariner, consisting of a plummet and line, continues to be chiefly in use for ascertaining the depth of the sea and the nature of the ground. With these, and the addition of a little grease applied to the lower extremity of the plummet, which strikes against the bottom, we learn the quality of the soil, though imperfectly, by the particles which adhere to the grease. What the navigator has yet been able to discover regarding the depth and the nature of the bottom of the German Ocean, I shall now endeavour to notice, being myself enabled to offer the result of a pretty extensive acquaintance with this field of inquiry.

“It may be necessary to premise, in treating of a subject so extensive, and in comparing great things with small, that we are obliged to speak of the North Sea as a bay or basin, and of the immense collection of débris which we meet with, extending over a great proportion of its bottom, under the common appellation of sand banks. We must also be allowed to consider the undulating line, or the irregularities of the bottom, to arise chiefly from the accumulation of deposited matters; and in most of the situations connected with these banks, we are supported and borne out in this conclusion, by their local positions relatively to the openings of firths, and the line of their direction in regard to the set or current of the ebb tide.

“The accompanying map (Plate XII.) of the eastern coast of Great Britain, with the opposite Continent, though208 upon a small scale, exhibits numerous soundings of the depth of the German Ocean; and the sections delineated on it will perhaps be found to give a pretty distinct view of the subject. This chart extends from the coast of France, in latitude 50° 57′ to 61° N. On the east, this great basin is bounded by Denmark and Norway, on the west by the British Isles, on the south by Germany, Holland, and France, and on the north by the Shetland Islands and the Great Northern or Arctic Ocean. The term German Ocean, though in very common use, is certainly not so comprehensive in its application to this great basin as that of North Sea, now more generally used by the navigator. The extent of this sea from south to north, between the parallels of latitude quoted above, is 233 leagues, and its greatest breadth from west to east, reckoning from St. Abb’s Head, on the coast of Scotland, to Ringhjo?bing Fiord, on the opposite shore of Denmark, is 135 leagues. The greatest depth of the water in this basin seems to be upon the Norwegian side, where the soundings give 190 fathoms; but the mean depth of the whole may be stated at only about 31 fathoms.

“To be more particular with regard to the depth of the German Ocean, or North Sea, it will be observed by the sections and soundings marked upon the chart, that the water gradually deepens as we sail from south to north. The first of these sections which we shall notice is on the parallel of three degrees of east longitude, running from Ostend to the latitude of the northmost of the Shetland Islands, being an extent of 227 leagues. The depth, as will be seen from this section (which, to avoid confusion209 in the body of the chart, is traced along the western side of it), varies rather after an irregular progression, from 120 fathoms towards the northern extremity of this sectional line, to 58, 38, 24, and 18 fathoms, as we proceed southwards, to within five miles of the shore, nearer which we do not approach in our remarks regarding the soundings. Notwithstanding the irregularity of the depth from the occurrence of numerous sandbanks, it is curious to observe the increase upon the whole as we proceed from south to north, by which this sea exhibits all the characteristic features of a great bay, encumbered with numerous sandbanks.

“In the same manner, though not strictly connected with our present purpose, we may observe that the English Channel deepens progressively from Dover to its entrance, formed by the Land’s End of England and the Isle of Ushant, on the coast of France; so that the Strait between Dover and Calais may be said to form a point of partition between two great inclined planes, forming the bottom of these seas.

“Besides the longitudinal, or north and south sectional line described above, we have also six other sections delineated in an easterly and westerly direction, across the accompanying chart, which are as follow. One between the Shetland Islands and the coast of Norway; a second between Tarbetness in Ross-shire and the Naze of Norway; a third extends from the Firth of Forth to the coast of Denmark; a fourth from the mouth of the river Tyne to Sylt Island, also in Denmark; a fifth from Flamborough Head, in Yorkshire, to the mouth of the210 River Elbe; and the sixth is from Yarmouth to Egmond-op-Zee, on the coast of Holland. Other sections of this sea have also been made, which include the general elevation of the land, as, for example, one of these extends from Holland across the German Ocean to the Thames, and through the interior of the country to the Bristol Channel; then crossing St. George’s Channel, this sectional line passes through the southern extremity of Ireland, and falls into the Atlantic Ocean; but this will be more particularly noticed, when I come to speak of the bed of the English Channel, in a future paper.

“On examining the accompanying cross sections of the depths of water on the same parallel they will be found to vary considerably. It may, however, be stated as a general conclusion, that there is a greater depth of water on the eastern and western sides of the German Ocean than in its central parts, and that, upon the whole, it is deeper on the British than on the continental shores, the coast of Norway excepted.

“We have already observed, that this sea is much encumbered with sandbanks, or great accumulations of débris, especially in the middle or central parts, and also along the shores towards what may be termed the apex of the bay, extending from the river Thames along the shores of Holland, etc., to the Baltic. One of these great central banks, delineated on the chart, and known to mariners as the Long Forties, trends north-east in the direction of the ebb tide from the entrance of the Firth of Forth no less than 110 miles, while the Denmark and Jutland banks may also be traced on the chart from the211 entrance of the Baltic, upwards of 105 miles in a north-western direction. Besides these, we have also another great central range of banks, which is crossed by no fewer than four of our sectional lines. These are known under the common appellation of the Dogger Bank, which is subdivided by the navigator into the Long Bank, the White Bank, and the Well Bank, including an extent of upwards of 354 miles from north to south. There are also a vast number of shoals and sandbanks, lying wholly to the southward of our section, between Flamborough Head and Heligoland. Altogether, therefore, the superficies of these extensive banks is found to occupy no inconsiderable portion of the whole area of the German Ocean; the surface of which, in making these investigations, has been estimated to contain about 153,709 square miles, while the aggregate superficial contents of the sandbanks alone amount to no less than 27,443 square miles, or include an area of about 5? of the whole surface of the North Sea.

“But to render these dimensions a little more familiar by comparison, we may notice, that the Island of Great Britain contains about 77,244 square miles, being not quite one half of the area of the North Sea; so that the area of the sandbanks bears a proportion equal to about one third of the whole terra firma of England and Scotland; and they are, therefore, perhaps, far more considerable in their extent than has been generally imagined.

“In speaking of the dimensions of sandbanks situate in the middle of the ocean, we are aware that great allowance must be made in forming a proper estimate of their212 extent, especially in speaking of their cubical contents. From a vast number of observations and comparisons relative to this subject, I have, however, been enabled to determine, that the average height of these banks measures about seventy-eight feet, from a mean taken of the whole. In ascertaining their height above the surrounding bottom, the measurement has been taken from the general depth around each respectively. Now, upon taking the aggregate cubical contents of the whole of these immense collections of débris, supposing the mass to be uniformly the same throughout, it is found to amount to no less a quantity than 2,241,248,563,110 of cubic yards, being equal to about fourteen feet of the depth of the whole German Ocean, or to a portion of the firm ground of Great Britain, on a level with the sea, taken twenty-eight feet in perpendicular height or depth, supposing the surface to be a level plane.

“These calculations at least tend to show that an immense body of water must be displaced, in consequence of these banks occupying so very considerable a proportion of the bed of the North Sea, the unavoidable effect of which must give a direct tendency to the tidal waters, and the flux produced by storms in the Atlantic, to overflow the bed of the German Ocean, in the same manner as if stones or other matter were thrown into a vessel already nearly brimful of water. This may further be illustrated by considering the actual state of any of the great inland lakes, as those of Geneva, Lochness, Lochlomond, etc., which for ages past have been receiving the débris of the surrounding mountains. We must doubtless213 allow that they contain a smaller portion of water, or are actually of a less depth than they were at an earlier period of the history of the globe. Accordingly, from inquiries, which, in the prosecution of this subject, I have been led to make regarding the two last mentioned lakes, it has satisfactorily appeared that their waters are subject to overflow or rise upon their banks. On Lochlomond, in particular, the site of a house at the village of Luss was pointed out to me, which is now permanently under the summer water mark, while the gable of another house in its neighbourhood is in danger of being washed down by the increase of the waters of the loch. Whether this striking appearance is to be attributed wholly to natural causes, or partly to artificial operations upon the bed of the river Leven, flowing from the loch, I have had no opportunity of inquiring. But the great bench or flat space round the margin of the loch, which is left partly dry during summer, forms altogether such a receptacle for débris as to be sufficient to affect the surface of the loch, and indeed permanently to raise its waters. We also infer, though by a different process, that the constant deposition going forward in the bed of the German Ocean must likewise displace its waters, and give them a tendency to enlarge their bed and to overflow their banks or boundary.

“In this view of the subject, it will appear that we have not only to account for the supply of an immense quantity of débris, but we must also dispose of the water displaced by the process of deposition which is continually going forward at the bottom of the ocean.

214 “With regard, then, to the supply of the débris of which these banks are composed.—We find that a very great portion of it consists of siliceous matters in the form of sand, varying in size from the finest grains to coarse bulky particles, mixed with coral and pounded shells, the quantity of these calcareous matters being altogether astonishingly great; and being specifically lighter than the particles of sand, the shells generally cover the surface of these sunken banks. With regard to the vast collection of siliceous particles connected with the banks, our surprise ceases when we consider the receptacle which the North Sea forms, to an almost unlimited extent of drainage from the surrounding countries, on which the change of the seasons, and the succession of rain and of drought upon the surface of the earth, are unceasingly producing their destructive effects. All have remarked the quantity of mud and débris with which every rill and river is charged, even after the gentlest shower; especially wherever the hand of the agriculturist is to be found. His labours in keeping up the fertilising quality of the ground consist in a great measure in preparing a fresh matrix for the chemical process or the germination of the seeds of the earth, in lieu of that portion of the finely pulverised soil which the rains are perpetually carrying to the sea, as the grand receptacle and storehouse of nature for these exuvi? of the globe. From the effect of rills and rivulets, we should, perhaps, rather be apt to expect a greater deposition in the bed of sheltered bays and arms of the sea than we really observe. So that we can readily believe that the quantity of débris, even for a single year,215 along such an extent of coast, may bear some consideration in respect to the bed of the German Ocean; what, then, must these effects produce in the lapse of ages?

“Whatever be the cause, the fact is certain, that on almost every part of the shores of Great Britain and Ireland, and their connecting islands, from the northernmost of the Shetland to the southernmost of the Scilly Islands, and also upon the shores of Holland, and part of France, particularly in the neighbourhood of Cherbourg, this wasting effect is going forward. These shores I have myself examined. But my inquiries have not been confined to the coasts which I have personally visited, having also, through the kind attentions of some nautical friends, been enabled to extend my investigations even to the remotest parts of the globe. The general result has been, that equally in the most sheltered seas, such as the Baltic and Mediterranean, and on the most exposed points and promontories of the coasts of North and South America, and the West India Islands, abundant proofs occur, all tending to show the general waste of the land by the encroachments of the sea. Such wasting effects are quite familiar to those locally acquainted with particular portions of the shores; and I have often received their testimony to these facts, as the sad experience of the removal of buildings, and the inundation of extensive tracts of land by the encroachment of the sea.

“Indeed, by a closer inquiry into this department of the subject, we shall, perhaps, find ourselves rather at a loss to account for the smallness of the quantity of this deposition, considering the waste which is constantly216 going forward in the process of nature, and even be led to seek for its wider distribution over the whole expanse of the bed of the ocean, as has been supposed in that theory of the globe, so beautifully and so ably defended by our late illustrious countryman Professor Playfair.

“One of the most striking and general examples of this kind may perhaps be found in the abrupt and precipitous headlands and shores which we everywhere observe along the coast, and which we suppose to have once been of the same sloping form and declining aspect with the contiguous land. In the production of these effects alone, an immense quantity of débris must have been thrown into the bed of the ocean. The channels which are cut by the sea in the separation of parts of the mainland, and the formation of islands, no doubt make way for a considerable portion of the displaced fluid; but still these channels, when filled with water, come far short, in point of bulk, when compared with the portions of the elevated land which are thus removed. Now, it has been alleged by some, that while the land is wasting at certain points, it is also gaining in others; and this is a state of things which is freely admitted to take place in various quarters; yet these apparent acquisitions are no more to be compared with the waste alluded to, than the drop is to the water of the bucket. But accurate observations regarding the formation of extensive sandbanks, and the accumulation of the débris, of which they are formed, are not to be made in a few years, perhaps not in a century, nor indeed in several centuries; for although the short period of the life of man is sufficient to afford the most incontrovertible217 proofs of the waste of the land where we become observers, yet when we extend our views to the depths of the ocean, and speak of the events and changes which are there going forward, we must not be supposed to set limits to time.

“We have many convincing proofs in the natural history of the globe, that the sea has at one time occupied a much higher elevation than at present. On the banks of the Firth of Forth, near Borrowstounness, for example, I have seen a bed of marine shells, which is several feet in thickness, and has been found to extend about three miles in length, and which is now situate many feet above the present level of the waters of the Forth. A recent illustration of this subject occurred also in the remarkable discovery of the skeleton of a large whale, found in the lands of Airthrey, near Stirling,—the present surface of the ground where the remains of this huge animal were deposited, having been ascertained (by my assistants, when lately in that neighbourhood) to be no less than twenty-four feet nine inches above the present level of the Firth of Forth at high water of spring tides. Now, whether we are to consider these as proofs of the higher elevation of the waters of the ocean in the most general acceptation of the word, at a former period, I will not here attempt to inquire. But aside from these anomalous appearances, there is reason for thinking that the waters of the higher parts of the Firth of Forth, like those of the Moray Firth, may, at one time, have formed a succession of lakes, with distinct barriers, as we find in the case of Lochness, and the other lakes forming the track of the Caledonian Canal. My object on the present occasion,218 however, is simply to notice the wasting effects of the North Sea upon the surrounding land, its deposition in the bottom of the sea, and the consequent production of surplus waters at the surface, and to endeavour to account for these appearances consistently with the laws of nature. The opinion accordingly which I have formed, and the theory which I have humbly to suggest (for I am not aware that this subject has been before particularly noticed) is, that the silting up of the great basin of the North Sea has a direct tendency to cause its waters to overflow their banks.

“Referring to the chart, we find that the North Sea is surrounded with land, excepting at two inlets or apertures, the one extending about 100 leagues, between the Orkney Islands and the Norwegian coast, and the other between Dover and Calais, which is of the width of seven leagues. The aggregate waterway of these two passages forms the track for the tidal waters, and also for the surplus waters produced during storms which affect the Atlantic and Arctic Oceans. It is also obvious that this waterway must remain nearly the same, and admit a constant quantity; or, to speak more correctly, by allowing these inlets to follow the general law, they must be enlarged by the waste or wearing of their sides, in a ratio perhaps greater than the silting up of the bottom in those particular parts, while the interior and central portions of the German Ocean are continually acquiring additional quantities of débris, along with the drainage water of the widely surrounding countries. If therefore the same, or a greater quantity of tidal and surplus219 waters continue to be admitted from the Atlantic and Arctic Seas into this great basin, where the process of deposition is constantly going forward, it is evident that the surface of the German Ocean must be elevated in a temporary and proportionate degree, and hence the production of those wasting and destructive effects which are everywhere observable upon its shores.

“This reasoning is also applicable, in a greater or less degree, to all parts of ............
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