5 8z THE POPULAR SCIENCE MONTHLY. 



constant evaporation, salts must in time have become so concentrated 

 that the water could hold no more in solution. Thi3 state of evapora- 

 tion 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 deposi- 

 tion 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 chief- 

 ly 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 for- 

 mations, I consider that the peroxide of iron which stains both salt 

 and marl may have been carried into the lakes in solution as car- 

 bonate 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 Dino- 

 sauria (land reptiles), Lizards (one of them a true land lizard, Teler- 

 peton), 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 Esiheria minuta might have lived 

 in any kind of area occupied by salt-water, while the small Marsupial 

 Mammal Microlestes mitiquus 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 Rhoetic 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 



