932 FOSSIL MEN. 



Sweden, and of the ancient Caledonians whose canoes 

 and implements we find in the estuaries of the Clyde 

 and Forth. Before their time there had been a con- 

 tinental period, in which the bed of the German Ocean 

 and Irish Sea had been dry land, and men had been 

 able to walk dryshod to Britain ; their ancestors had 

 witnessed a great, and probably sudden depression of 

 the land, and in their day it was again slowly rising. 

 In subsequent generations it rose still further, and 

 what had been in their day under the sea at Abbeville, 

 became a bog, while the Somme valley, raised to a 

 higher level, became reduced to its present form, and 

 the river shrunk into a deeper channel, its volume be- 

 coming greatly diminished by the increasing dryness 

 of the climate and removal of the forests, changes 

 which also extirpated the last survivors of those species 

 of quadrupeds which had been suited for a wilder and 

 more wooded country. 



These changes are well summed up by Sir C. Lyell, 



his " Antiquity of Man/' pages 331 et seq., and by 



tabulating his succession we may clearly understand 



the position of the supposed Amiens flint-chippers. 



(See Table on opposite page.) 



All this leaves us, however, still in uncertainty as 

 to the absolute time involved. Our estimate of this 

 must depend on the rapidity or slowness of the os- 

 cillations in the Modern period (No. 4) . If we adopt 

 with Lyell a strictly uniformitarian method, and esti- 

 mate the elevations and depressions of which there 

 is geological evidence at thirty inches per century, 



