Page:Popular Science Monthly Volume 3.djvu/597

Rh Taking all these circumstances into account, the poverty of the marine fauna, the terrestrial lizards, the Amphibia, and the land-plants, I cannot resist the conclusion that the Permian rocks of England were deposited in a lake or in a series of great inland continental lakes, brackish or salt; and, if this be true, it will equally apply to some other regions of Europe.

The strata that succeed the Permian formations in the geological scale are those included in the word Trias, on the continent of Europe. These consist of three subdivisions: first and lowest, the Bunter sandstone; second, the Muschelkalk; and third, the Keuper marl, or Marnes irisées. The Bunter sandstone on the Continent consists chiefly of red sandstones, with interstratified beds of red marl and thin bands of limestone, sometimes magnesian. These form the Grès bigarré of France. In these strata, near Strasbourg, about thirty species of land-plants are known, chiefly ferns, Calamites, Cycads, and Coniferæ, and with them remains of fish are found and Labyrinthodont Amphibia. In the same series there occur Lamellibranchiate marine mollusca of the genera Trigonia, Mya, Mytilus, and Posidonia, so few in number that they suggest the idea, not of the sea, but of an inland salt lake, especially when taken in connection with the Labyrinthodont Amphibia and the terrestrial plants.

The Muschelkalk, next in the series, is essentially marine. A partial submergence took place, and a large and varied fauna of Mesozoic type occupied the area previously covered by the lake deposits of the Bunter sandstone.

Above this comes the Keuper series, with Gypsum and dolomite, land-plants, fish, and Labyrinthodont remains, and a few genera and species of marine shells, again suggesting the idea of a set of conditions very different from those that prevailed when the Muschelkalk was formed.

These strata, as a whole, are the geological equivalents of the New Red Sandstone and Marl of England, with this difference—that the Muschelkalk is entirely absent in our country, and we only possess the New Red Sandstone (Bunter) and the New Red Marl (Keuper).

The kind of arguments already applied to part of the Permian strata may, with equal force, be used in relation to the New Red Sandstone and Marl of England. I have for long held that our New Red Sandstone was deposited in an inland lake, probably salt, and that our New Red Marl was certainly formed in a salt lake. Pseudo-morphous crystals of salt are common throughout the whole formation, which, besides, contains two great beds of rock-salt, each 80 or 100 feet thick, which could only have been deposited in a lake that had no outflow, and from which all the water poured into it by the rivers of the country was entirely got rid of by evaporation induced by solar heat. It has been proved by analyses that all spring and river waters contain chloride of sodium and other salts in solution, and in such a lake, by