‘_Incedimus_ per ignes Suppositos cineri doloso.’
CHAPTER IV. SUBTERRANEAN UPHEAVALS AND DEPRESSIONS.
Oscillations of the Earth’s Surface taking place in the present day— First ascertained in Sweden—Examples of Contemporaneous Upheaval and Depression in France and England—Probable Causes of the Phenomenon.
While the sea and the atmospheric ocean are subject to perpetual fluctuations, and the poet justly compares the uncertain tenure of human prosperity with the restless wave or the inconstant wind, the solid earth is generally regarded as the emblem of stability. But an examination of the various strata of aqueous origin which constitute by far the greater part of the actual dry land soon shows the fallacy of this opinion.
The fossils of marine origin which occur in so many of our oldest rocks, now situated far above the level of the ocean, must necessarily have been raised from the deep. On the towering Andes, fifteen thousand feet above the tide-marks of the Pacific, the geologist finds sea-shells imbedded in the rock, and high above the snow-line the chamois-hunter of the Alps wonders at the sight of spirally-wound Ammonites that once enjoyed life at the bottom of the Liassic Sea. In strata of a more modern date, we find, on the banks of the river Senegal, far inland, large deposits of the _Arca senilis_, a mollusc still living on the neighbouring coast. On the borders of Loch Lomond, twenty feet above the level of the sea, shells of the edible cockle and sea-urchin repose in a layer of brown clay, and the banks of the Forth and of the Clyde, thirty feet higher than the storm tides, inclose remains of common shells of the present period, such as the oyster, the mussel, and the limpet. Along the shores of the Mediterranean, at Monte Video and at Valparaiso, in the isles of the Pacific and at the Cape, in California and Haiti, we meet with similar instances of elevation, which, though geologically recent, may yet be of a sufficiently ancient date to have preceded the appearance of man on earth. But proofs are not wanting that the upheaving power which has wrought so many changes in the past is still actively employed in remodelling the surface of the earth.
This important geological fact was first ascertained on the coast of Sweden, where the peculiar configuration of the shore makes it easy to appreciate slight changes in the relative level of land and water. For the continent is fringed with countless rocky islands, called the ‘skär,’ within which boats and small vessels sail in smooth water even when the sea without is strongly agitated. But the navigation is very intricate, and the pilot must possess a perfect knowledge of the breadth and depth of every narrow channel, and the position of innumerable sunken rocks. On such a coast even a slight change of level could not fail to become known to the mariner, and to attract the attention of the learned, as soon as the book of nature began to be more accurately studied.