Page:Popular Science Monthly Volume 3.djvu/594

578 I will now discuss the conditions under which the British Permian strata were deposited. These rocks in their general characters very much resemble the Rothliegende, Kupferschiefer or Marl-slate, and Zechstein of the Thuringerwald and other parts of Germany, with this difference, that where the English Magnesian Limestone (Zechstein) is in force between Tynemouth and Nottingham, there are no red sandstones, marls, and conglomerates (Rothliegende), between the limestone and the Coal-measures, and in all the other parts of Britain where the red sandstones, etc., occur, there is only in two instances a little magnesian limestone lying, not at the top, but in the midst of, or interstratified with, the sandy and marly series.

The Permian marls, sandstones, conglomerates, and subangular breccias of Warwickshire, Staffordshire, Shropshire, Lancashire, North Wales, the Vale of Eden, and the south of Scotland, are all red, and, in fact, I nowhere recollect any important gray, yellow, or brown shales and sandstones among them. It is, however, foreign to my present purpose to discuss minor stratigraphical details, or any questions connected with English and Continental equivalent geological horizons of Permian age, nor is it necessary to do more than allude to the disturbances and denudations which preceded the unconformable deposition of our Permian strata, on all or any of the Palæozoic formations of earlier date. It is enough if I am able to show good reason for my belief that all of our Permian strata were deposited, not in the sea, but in the inland waters of lakes, which were probably mostly salt, but may possibly sometimes have been fresh or brackish.

As with the red strata of the Old Red Sandstone, so I consider that the red coloring-matter of the Permian sandstones and marls is due to the precipitation of peroxide of iron in a lake or lakes, in the manner already stated, and the nearly total absence of sea-shells, in by far the largest part of the areas occupied by the strata colored red, strongly points to this conclusion. There is other evidence bearing upon the question. The British plants of Permian age were mostly of genera common in the Coal-measures, though of different species. Among them there are Calamites and Lepidodendron, Walchia, Chondrites, Ullmania, Cardiocarpon, Alethopteris, Sphenopteris, Neuropteris, and many fragments of undetermined coniferous wood. This, however, forms no perfectly conclusive proof of the lacustrine origin of the strata, though it is not unlikely that land-plants, drifted by rivers, should have been water-logged and buried in the sediments of lakes.

The evidence derived from Reptilian remains more strongly points in the same direction. First we have the Labyrinthodont Amphibian, Dasyceps Bucklandi, from the Permian sandstones near Kenilworth; next the footprints mentioned by Prof. Harkness in the red sandstones of the Vale of Eden; and again, the numerous footprints in the sandstones of Corncockle Moor, in Dumfriesshire, long ago described by Sir William Jardine. All of these prints indicate that the Amphibia