Page:Popular Science Monthly Volume 3.djvu/598

582 constant evaporation, salts must in time have become so concentrated that the water could hold no more in solution. This state of evaporation is now going on in the comparatively rainless areas of the Dead Sea, the Great Salt Lake of Utah, and in numerous lakes in Central Asia, though it is by no means asserted that in all of these positive deposition of salt has begun to take place. At length saline deposits began to be formed, which in the case of the New Keel Marl consisted chiefly of common salt. This is impossible in an ordinary ocean, for the salt in solution cannot there be sufficiently concentrated to permit of deposition.

Gypsum and other salts contained in the red marl may also have been formed in like manner, and, as in the Permian and Old Red formations, I consider that the peroxide of iron which stains both salt and marl may have been carried into the lakes in solution as carbonate of iron, to be afterward deposited as a peroxide.

The remains of plants found in the British Keuper beds also speak of a surrounding land, while the Crocodile (Stagonolepis), the Dinosauria (land reptiles), Lizards (one of them a true land lizard, Telerpeton), and six supposed species of Labyrinthodont Amphibia, all tell the same tale of land. Rain-prints and sun-cracks are not wanting to help in the argument; and while the fishes yield no conclusive proof, the well-known bivalve crustacean Estheria minuta might have lived in any kind of area occupied by salt-water, while the small Marsupial Mammal Microlestes antiquus speaks conclusively of land.

Taken as a whole, it seems to me that the nearest conception we can form, of part of the old continent in which the Permian and New Red strata were deposited, is, that it physically resembled the great area of inland drainage of Central Asia, in which, from the Caspian 3,000 miles to the eastward, almost all the lakes are salt in a region comparatively rainless, and in which the area occupied by inland salt or brackish waters was formerly much more extensive than at present.

And now let me endeavor to sum up the whole of the argument. If, as I believe, the Old Red Sandstone was deposited in a lake or lakes; if the Coal-measures, as witnessed by the great river-beds, estuarine shoals, and wide-spread terrestrial vegetation, show proof of a continental origin; if the Permian strata were formed in inland salt or brackish waters, and if the New Red beds had a similar origin—then from the close of the Uppermost Silurian formation down to the influx of the Rhœtic Sea, which brought the Keuper Marl period to an end, there existed over the north of Europe, and in other lands besides, a great continent throughout all that time, one main feature of which was the abundance of Reptilian and Amphibian life. This old continent was probably comparable in extent to any of the largest continents of the present day, and perhaps comparable in the length of its duration to all the time represented by all the Mesozoic strata from the close of the Triassic epoch down to the latest strata of the