PALAEOLITHIC RACES 327 



No doubt, in a retrospective glance we are liable to a decep- 

 tive effect of perspective, and events widely separated in fact 

 appear unduly crowded together by foreshortening. We are not, 

 however, altogether without the means of making an appropriate 

 correction for this illusion. The geological scale of time, though 

 far from exact, is sufficiently so for the purpose, and, judged 

 by this standard, the duration of the latest epoch of terrestrial 

 history, known as the Pleistocene, may be regarded as but little 

 short of half a million of years. It corresponds with the chief 

 period of human development, and includes four complete 

 oscillations of climate, each possibly of the average duration of | 

 a hundred thousand years. 



Of the many changing elements which contribute to the 

 geology of the Pleistocene epoch, climate is one of the most 

 important, and to this, therefore, in the first place, we will turn 

 our attention. The recent existence of a great Ice age was first 

 divined by Schimper, the poet-naturalist, whose enthusiasm 

 fired the imagination and stimulated the researches of the 

 indefatigable Agassiz. 



As a result of his investigations, Agassiz announced his 

 belief that the earth had passed at no distant date through a 

 period of extreme cold, when ice and snow enmantled a large 

 part of its surface. Attempts, persisting even down to the 

 present day, have been made to overturn or belittle this con- 

 clusion, but with very imperfect success, and it now stands 

 more assured than ever, as is shown by the increasing testimony 

 of concordant observations. 



The evidence on which Agassiz based his views was derived, 

 in the first instance, from a study of the Swiss glaciers and of 

 the effects associated with their existence. The contemporaries 

 of Agassiz — Forbes and Tyndall — and subsequent generations of 

 scientific explorers have pursued their researches in the same 

 region ; and this land of lofty peaks, which has furnished in- 

 spiration to so many great discoverers in other branches of 

 geology, is thus pre-eminently classic ground for the glacialist. 

 Let us then commence our studies in the Alps, and, as a 

 preliminary to further studies, make ourselves acquainted with 

 phenomena now alien to our land. 



When Agassiz began his researches, glaciers were but little 

 known, even to the travelled Englishman ; now a crowd of 

 summer visitors makes holiday upon them. It matters little to 



