CHAP. XII. OP THE GLACIAL AND HUMAN PERIODS. 207 



no means encountered at the same point of time in every 

 district. In the case of the Danisia peat, for example, we 

 get no farther back than the recent period of our Chrono- 

 logical Table (p. 7), and then meet with the boulder clay; 

 and it is the same in the valley of the Clyde, where the 

 marine strata contain the ancient canoes before described 

 (p. 48), and where nothing intervenes between that recent 

 formation and the glacial drift. But we have seen that in the 

 neighborhood of Bedford (p. 164) the memorials of man can 

 be traced much farther back into the past, namely, into the 

 post-pliocene epoch, when the human race was contemporaiy 

 with the mammoth and many other species of mammalia now 

 extinct. Nevertheless, in Bedfordshire, as in Denmark, the 

 formation next antecedent in date to that containing the 

 human implements is still a member of the glacial drift, with 

 its erratic blocks. 



If the reader remembers what was stated in the Eighth 

 Chapter (p. 144.) as to the absence or extreme scarcity of 

 human bones and works of art in all strata, whether marine 

 or fresh-water, even in those formed in the immediate prox- 

 imity of land inhabited by millions of human beings, he will 

 be prepared for the general dearth of human memorials in 

 glacial formations, whether recent, post-pliocene, or of more 

 ancient date. If there were a few wanderers over lands 

 covered with glaciers, or over seas infested with icebergs, 

 and if a few of them left their bones or weapons in moraines 

 or in marine drift, the chances, after the lajise of thousands 

 of years, of a geologist meeting with one of them must be 

 infinitesimally small. 



It is natural, therefore, to encounter a gap in the regular 

 sequence of geological monuments bearing on the past history 

 of man, wherever we have proofs of glacial action having 

 prevailed with intensity, as it has done over large parts of 

 Europe and North America, in the post-pliocene period. Aa 



