OCR Text |
Show OG ISLAND LIFE. (rAHT I. field slate, with plants, insects, and marsupials; and the Oolitic coal of Yorkshire and Sutherlandshire. Beds of the same age occur in the Rocky Mountains of North America, containing abundance of Dinosaurians and other reptiles, among which is the Atlantosaurus, the largest land-animal ever known to have existed. Professor 0. C. Marsh describes it as having been between fifty and sixty feet long, and when standing erect at least thirty feet high 11 Such monsters could hardly have been developed except in an extensive land area. A small mammal, Dryolestes, bas been discovered in the same deposits. A rich Jurassic flora bas also been found in East Siberia and the Amur valley. The older Triassic deposits are very extensively developed in America, and both in the Connecticut valley and the Rocky Mountains show tracks or remains of land reptiles, amphibians and mammalia, while coalfields of the same age in Virginia and Carolina produce abundance of plants. Here too are found the ancient mammal, Microlestes, of Wurtemberg, with the ferns, conifers, and I~abyrinthodonts of the Bunter Sandstone in Germany; while the beds of rock-salt in this formation, both in England and in many parts of the continent, could only have been formed in inland seas or lakes, and thus equally demonstrate continental conditions. We now pass into the oldest or Palreozoic formations, but find no diminution in the proofs of continental conditions. The Permian formation bas a rich flora often producing coal in England, France, Saxony, Thuringia, Silesia, and Eastern Russia. Coalfields of the same age occur in Ohio in North America. ln the still more ancient Carboniferous formation we find the most remarkable proofs of the existence of our present continents at that remote epoch, in the wonderful extension of coal beds in all the known continents. We find them in Ireland, England, and Scotland; in France, Spain, Belgium, Saxony, Prussia, Bohemia, Hungary, Sweden, Spitzbergen, Siberia, Russia, Greece, Turkey, and Persia; in many parts of continental India, extensively in China, and in Australia, Tasmania and 1 Introduction and Succession of Vertebrate Life in America, by Professor 0. C. Marsh. Reprinted from the Popular Science Monthly, March, April, 1878. cuAr. vr.J GEOGHAPIIICAL AND GEOLOGICAL CHANGES. Now Zealand. In North America thoro arc immense 1 fi ld . coa e s m Nova Scotia a~d Ne.w Brunswick, from Pennsylvania southward. to Alabama, m Indiana and Illinois, and in Missouri; and there IS also a true coal formation in South Brazil. This ~onderfully. wide distribu~ion of coal, implying, as it docs, a nch vegctat.wn and extensive land areas, carries back tho proof of the persistence and general identity of our continents to a period so remote that none of the higher ani mal typos bad probably been developed. But we can go even further back than this, to the preceding Devonian formation, which was almost certainly an inland deposit often containing remains of fresh-water shells, plants, and even insects; while Professor Ramsay believes that he bas found "sun-cracks and rainpittings" in the Longmynd beds of the still earlier Cambrian formation.1 If now, in addition to the body of evidence hero adduce~, we t~ke into consideration the fresh-water deposits that still remam to be discovered, and those extensive areas where they have been destroyed by deuudation or remain deeply covered up by later marine or volcanic formations we cannot but be struck by the abounding proofs of the perman~ncc of the great features of land and sea as they now exist; and we shall s~e how utterly gratuitous, and how entirely opposed to all the evidence at our command, are the hypothetical continents briuging over the deep oceans, by the help of which it is so often attempted to cut the Gordian knot presented by some anomalous fact in geographical distribution. Oceanic Islands as Indications of the P eTmanence of Continents and Oceans.-Coming to the question from the other side Mr. Darwin has adduced an argument of considerable weiah~ . f b m . a:our of t.he permanence of the great oceans. He says (Ong~n of Spemes, 6th Ed. p. 288): "Looking to existing oceans, which are thrice as extensive as the land, we see them studded with many. islands; but hardly one truly oceanic island (with the exceptwn of New Zealand, if this can be called a truly oceanic island) is as yet known to affor 1 eYen a fraament of ~ny Palreozoic. or Secondary formation. Hence we ma; perhaps wfer that dunng the Pal::eozoic and Secondary periods neither 1 Physical Geo[traphy and Geology of Great Britain, 5th Eo. p. Gl. H |