GF.OLOGlrAL CHANOK, AND TIME. 123 



soutliern sliores of Englaiul, and across the Baltic into France and Ger- 

 many. This Arctic transformation \\'as not an episode that lasted merely 

 a few seasons, and left the land to resninc thereafter its ancient aspect. 

 Witli \arioiis successive tiuctuations it must have endured for many 

 thousands of years. When it begjan to disappear it i)robably faded 

 awa.N as sl()\\i>- and imperceptibly as it had advanced, and when it 

 hnall.N \anished it left Europe and Xortli America jnofoundly chan<ied 

 in the character alike of their scenery and of their iidiabitants. The 

 ru.uii'ed rocky contours of earlier times \vvv(\ i^rouiid smooth and pol- 

 ished by the march of the ice across them, Avhile the lower grounds were 

 buried under wide and thick sheets of clay, j^ravel, and sand, left l)e- 

 hind by the meltin,«i- ice. The \ aried and abundant tlora which had 

 spread so far within the Arctic? circle was driven away into more 

 southern and less un,i;enial climes. But most nienu)rable of all was 

 the extirpation of the prominent large animals which, before the ad- 

 vent of the !<•»', had roanu'd over Europe. The lions, hyenas, wild 

 horses, hipi)opotaniuses, and other creatures either became entirely ex- 

 tinct or were <lriven into the Mediterranean basin and into Africa. In 

 their i)lact^ came northern forms — the reindeer, glutton, musk ox, woolly 

 rhinoceros, and mammoth. 



Such a marvellous transformation in climate, in scenery, in vegetation 

 and in inhabitants, within what was after all but a brief portion of geo- 

 logical time, though it may have involxed no sudden or violent convul- 

 sion, is sundy entitled to rank as a. catastrojjhe in the liistory of the 

 globe. It was ])rol)ably brought about mainly if not entirely by the 

 oi)eration of forces exteriuil to tln^ earth. No similar cahimity having 

 befallen the continents v.ithin the time during which man has been 

 recording his e\perieiu;e, the Ice Age might be cited as a contradiction 

 to the iloctrine of unifornuty. And yet it manifestly nrrixt'd as part of 

 the estal)Iished ordered' Xature. Whether or n(»l we graid that other 

 ice ages lueceded the last great one, we must admit that the conditions 

 um.ler w Iiieh it arose, so far as we know them, ndght conceivably have 

 occui-red before and may occur again. The- various agencies called 

 into i)lay by tin- extensive icfrigeration of the northern hemisphere 

 were not different from those with which we are familiar. Snow fell 

 and glaciers cre])t as they do to-day. Ice scored and ])olished rocks 

 exac tly as it still does among the Alps and in Norway. There was 

 nothing abnormal in the phenomena, save the scale on which they 

 were manil'ested. .\nd thus, taking a broad view of (he whole subje<'t, 

 we recognize the catastrophe, while at the same time we see in its i)rog- 

 ress the operation of those same natural ])r()cesses w hich we know to 

 be integral jtarts of the machinery whereby the surface of the earth is 

 continually tian stormed. 



Among the tlebtswjiich science owes to the lluttoiiiau scliool. not 

 the least memorable is the promulgalion of the tirst w ell iounde<l con- 



