78 THE POST-PLIOCENE PERIOD. 



appeals to the same kind of evidence with reference to the climate of 

 the Post-tertiary period, and let us inquire what is its testimony. 



The first and most general answer usually given is, that the Post- 

 pliocene chmate was colder than the Modern. The proof of this in 

 Western Europe is very strong. The marine fossils of this period in 

 Britain are more like the existing fauna of Norway or of Labrador 

 than the present fauna of Britain. Great evidences exist of driftage 

 of boulders by ice, and traces of glaciers on the higher hills. In 

 North America the proofs of a rigorous climate, and especially of the 

 transport of boulders and other materials by ice, are equally good, 

 and the marine fauna all over Canada and New England is of boreal 

 type. In evidence of these facts, I may appeal to the papers and 

 other publications of Sir C. Lyell and Professor Ramsay on the for- 

 mations of the so-called Glacial period in Europe and America,* and 

 to my own previous papers on the Post-tertiary of Canada. 



Admitting, however, that a rigorous climate prevailed in the Post- 

 pliocene period, it by no means follows that the change has been 

 equally great in different localities. On the contrary, while a great 

 and marked revolution has occurred in Europe, the evidences of such 

 change ai-e very much more slight in America. In short, the causes 

 of the coldness of the Post-pliocene seas to some extent still remain 

 in America, while they must have disappeared or been modified in 

 Europe. 



If we inquire as to these causes as at present existing, we find them 

 in the distribution of ocean-currents, and especially in the great warm 

 current of the Gulf Stream thrown across from America to Europe, 

 and in the Arctic currents bathing the coasts of America. In con- 

 nexion with these we have the prevailing westerly winds of the tem- 

 perate zone, and the great extent of land and shallow seas in northern 

 America. Some of these causes are absolutely constant. Of this 

 kind is the distribution of the winds, depending on the earth's 

 temperature and rotation. The courses of the currents are also 

 constant, except in so far as modified by coasts and banks ; and the 

 direction of the drift-scratches and transport of boulders in the Post- 

 pliocene both of Europe and America show that the Arctic currents at 

 least have remained unchanged. But the distribution of land and 

 water is a variable element, since we know that in the period in 

 question nearly all northern Europe, Asia and America, were at one 

 time or another under the waters of the sea ; and it is consequently to 



* Lyell's Travels in North America; Eamsay on the Glaciers of Wales, and on the 

 Glacial Phenomena of Canada. See also Forbes on the Fauna and Flora of the 

 British Islands, in Memoks of Geological Survey. 



