LETTER XLI. THE veil which has thus been rent from one of the secrets of nature, shews to us in vivid, but in awful colours, the subterranean vicissitudes of the globe. Nor are the benefits resulting from such discoveries inconsiderable. Whatever turns the mind intensely upon unvisionary contemplation, tends to concentrate its powers, and to fit it for bolder and more exalted flights: The developement of physical causes, opens and enlarges the boundaries of human reason. Until the present century-or rather, indeed, late in the last the internal structure of this earth had not been examined with attention. And yet it is there where the chronicles of the world are to be found; where we are to seek for a knowledge of the revolutions of ages; where we are to read, in letters legibly written, the changes, however disastrous, of nature; and where alone the proofs of the antiquity and the pre-existence of nations are to be traced. At what profound depths are the soils of ancient worlds! L4 worlds! our confined imaginations, accustomed to the immediate and general state of earthly repose, are scarcely able to fathom them. Yet man is, or has been every where: the whole globe has been his cradle. No one part of the mass has been less indigenous to him than another. The bottom of the sea he can claim as his, as well as the continental land. The strata beneath the very lowest that have yet been explored, were once as appropriate to his use, as the surface or outermost rind on which he treads at present. In the dreary regions which cover and hide from observation, the tremendous laboratories and furnaces of nature, the alternate strata of lava and soil have been considered as sufficient data for proving the antiquity of the world; taking for granted, that the quantity of soil contained in each stratum has been produced by length of time only; not considering that eruptions of sand, ashes, or mud, are equally frequent with those of liquid fire, and that such productions become immediately fit for vegetation. It appears much more probable that volcanic soil strata proceeded from subsequent eruptions, than from length of time. * And, indeed, this idea is to be supported from the relatively smail surface • Whitehurst. surface which ejected lavas present to the atmosphere. These require many years to cool; and many hundreds of years to effect their total decomposition. At the same time, that their decomposition will be quicker or slower, in proportion as they have been more or less perfectly melted. Sir William Hamilton says, "the dense lava of Vesuvius forms one or two feet of mould in a thousand years." The globe, we thus perceive, at least to a certain depth, is not every where solid; but is intermixed with mighty caverns, whose arches support the incumbent earth, which in the progress of time inevitably give way. Then instantly rush in the waters, and by filling them, leave a quantity of dry land, which shortly becomes an habitation for terrestrial animals. These, in their turn, undergo a similar fate. Thus succeeds revolution to revolution. When the masses of shells were heaped upon the Alps, then in the bosom of the ocean, there must have been portions of the earth, unquestionably, dry and inhabited: vegetable and animal remains prove it: no stratum hitherto discovered, with other strata upon it, but has been, at one time or other, the surface. The sea an nounces every where, its different sojournments: and : and at least yields conviction, that all strata were not formed at the same period. At what a profound depth are beds of coal, the formation of which must have been posterior to the formation of the vegetables, of which they are composed, and which vegetables must have flourished on the surface of the earth, or on the bottom of the sea. In the country about Namur there are coal pits at the depth of two thousand feet. At Whitehaven, a vein of coal runs even a quarter of a mile under the sea. But, all strata of limestone, chalks, marbles; all gypsums, spars, alabasters, &c. are, confessedly of animal origin: those of coal, and of all bituminous fossils, and the mould every where covering the surface of the earth and other substances, are supposed, as we have already seen, to have arisen entirely from the destruction of animals and vegetables. Fire, and water, have in this manner left the most indubitable marks of their respective and conjoint ravages on the earth. The former, however, has, to external appearance, worked only in some parts of the surface; while the latter, in its crystallizations, has scattered its offspring of granite almost universally. Yet, if the volcanic theory of basaltes be well founded, and and no doubt the arguments in favour of it are convincing, at least to me they are irrefragable, a scene of horror is presented to our view, which must fill us with astonishment; since on this system it will be found, that there is hardly a country on the face of our globe, which has not at some time or other been wasted by the fury of subterranean fire.* For instance, independent of those we have already mentioned, what innumerable volcanic remains in Asia, in the Philippine, in the Molucca, in the Japan, in the Bourbon, and in the Sumatra islands. In Africa, how prominently they appear. Teneriffe, which, according to Heberden, is 15396 feet above the level of the sea, or nearly three miles. Madeira, St. Helena, the Azores, Johanna, and the Comoro islands, &c. besides what may be yet undiscovered in the interior parts of the continent. In America, particularly the Southern America, what a volcanic chain! the grandest that exists in nature, with Cotopaxi for its principal link. How interesting would a volcanic map of the two hemispheres be! What a world it would shew us! If again those apparent vestiges of marine productions, which are observed indiscriminately scattered through the earth at all depths below its surface, and on the summit |