“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 aërial 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 and 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.
“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, though 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 Ringhjoöbing 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 confusion 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.