466 



HISTORICAL GEOLOGY 



8. Elephants are at present confined to the tropical region. 



Do the bones of elephants 

 in Alaska and northern Si- 

 beria therefore indicate a 

 tropical climate there in re- 

 cent times? 



9. Of the caves with rela- 

 tions as indicated in Figures 

 483 and 484, which affords 

 the better evidence of the 

 Glacial age of the human 

 species, and why ? 



FIG. 482. Relations of trees to a bed of 

 volcanic ash near Lassen Peak, California. 



10. Applying the principles already learned from the past 

 history of animals, how can you account for the fact that the 



FIG. 483. Section 



a cave in FIG. 484. Section of a cave in lime- 



limestone, showing earth (A) con- 

 taming bones of men and extinct 

 mammals, overlain by a crust of 

 stalagmite (B), and the mouth of 

 the cave closed by a deposit of till. 



Australian race of man has made 

 less advancement than any other? 

 11. In California the Quater- 

 nary glaciers were abundant on 

 mountains eight to ten thousand 

 feet high, while in Nevada the 

 only peaks which had even small 

 glaciers were more than eleven 

 thousand feet high. Why should 

 there be this contrast ? 



stone, the floor of which is covered 

 with earth (A) containing human 

 bones and implements. 



FIG. 485. Map of the distribution 

 of bowlders scraped off from an out- 

 crop of igneous rock by a glacier. 



12. In a locality in England bowlders derived from a small 

 volcanic plug of peculiar rock are found distributed in the glacial 

 drift as shown in Figure 485. Explain the fan-shaped distribution. 



