LECTURE XI. 321 



there is no reason to suppose that the climate difiered widely 

 from the present ; at any rate, it may be safely assumed that 

 thousands of years were required for the formation of the afore- 

 said beds. 



But whether six or ten thousand years were requisite for their 

 formation, these slate-coals occupied but a small fraction of the 

 diluvial period. They overlie thick glacial clay, and are them- 

 selves covered with flint and sand-banks, thirty feet high and 

 with floated glacial blocks on the top. Despite of the immense 

 period of time which separates these coal deposits from histori- 

 cal time, during which not even the thin stratum of vegetable 

 earth was completely formed, these coal formations still belong 

 to our geological period, though to the beginning of it ; for we 

 have seen that there grew in them the same marsh and peat 

 plants, and the same trees, as are still extant in that region. 

 We should, nevertheless, add, that there occur some species, as 

 the hazel, which difiPer from living species ; but the same 

 character which manifests itself in the animal world shews 

 itself also in the vegetable kingdom. Some sjDCcies have 

 become perfectly extinct, others have retreated northward, 

 or to the mountains, but most continue to live in the same 

 region. 



The coal beds in eastern Switzerland are specially interest- 

 ing on account of the animal world they contain. Small fresh- 

 water snails of still living species are as abundant as small 

 marsh-beetles, whose glittering wing-sheaths, often closely 

 compressed, form the surface of the beds. There occur, also, 

 coleoptera, which belong to extinct species, like the trunk- 

 beetle, etc. There were also found teeth of the deer and bear, 

 remains of the elephant and rhinoceros (not of the mammoth 

 and the rhinoceros with a bony septum), but of an elephant 

 resembling the Asiatic (Elephas antlquus) , and the rhinocer.os 

 with a semi-osseous septum (Bliinoceros leptorhinusj , both of 

 which occur with the bones of man, but seem to have become 

 extinct at an earlier period than their hairy cognates. From 

 this fact follows the deduction, confirmed indeed by the strati- 

 fication, that the slate coals of eastern Switzerland had been 

 formed upon the glacial clay immediately after the retreat of 



Y 



