GEOLOGICAL TIME. 421 



the retreat of the reindeer and the musk ox are probably in 

 great measure owing to the change of climate. These and 

 similar facts, though they afford us no means of measurement, 

 impress us with a vague and overpowering sense of antiquity. 

 All geologists, indeed, are now prepared to admit that man 

 has existed on our earth for a much longer period than was 

 until recently supposed to have been the case. 



But it may be doubted whether even geologists yet realize 

 the great antiquity of our race. 



"When speculations on the long series of events which 

 occurred in the glacial and post-glacial periods are indulged 

 in," says Sir C. Lyell,* " the imagination is apt to take alarm 

 at the immensity of the time required to interpret the monu- 

 ments of these ages, all referable to the era of existing species. 

 In order to abridge the number of centuries which would 

 otherwise be indispensable, a disposition is shown by many 

 to magnify the rate of change in pre-historic times, by invest- 

 ing the causes which have modified the animate and the in- 



o 



animate world with extraordinary and excessive energy 



We of the living generation, when called upon to make grants 

 of thousands of centuries, in order to explain the events of 

 what is called the modern period, shrink naturally at first 

 from making what seems so lavish an expenditure of past 

 time." 



That palaeolithic implements belong to a period of great 

 cold, i.e. to the glacial period, seems indicated by the fact that 

 they have not yet been found in the areas occupied by the 

 deposits of the late glacial epoch. If a map be constructed 

 showing the regions occupied by the deposits of the glacial 

 epoch, the morainic debris, diluvial gravels, and boulder clay, 

 on the one hand, and the palaaolithic implements on the other, 

 it would be seen at a glance that the former end when the 

 latter begin. 



* Address to the Brit. Ass. 1864, p. 21. Bath. 



