RELICS OF MAN IN THE GLACIAL PERIOD. 285 



ering. It is suggested, however, by Sir William Daw- 

 son, that he may have been adapted to arctic climates 

 by a fatty covering, as the walrus is at the present time. 

 A difficulty in accounting for many of the remains of 

 the hippopotamus in some of the English caverns is 

 that they are so far away from present or possible 

 water-courses. But it would seem that due credit has 

 not been ordinarily given to the migratory instincts 

 of the animal. In southern Africa they are known to 

 " travel speedily for miles over land from one pool of a 

 dried-up river to another ; but it is by water that their 

 powers of locomotion are surpassingly great, not only in 

 rivers, but in the sea. . . . The geologist, therefore, may 

 freely speculate on the time when herds of hippopotami 

 issued from North African rivers, such as the Nile, and 

 swam northward in summer along the coasts of the Medi- 

 terranean, or even occasionally visited islands near the 

 shore. Here and there they may have landed to graze 

 or browse, tarrying awhile, and afterwards continuing their 

 course northward. Others may have swum in a few sum- 

 mer days from rivers in the south of Spain or France to 

 the Somme, Thames, or Severn, making timely retreat to 

 the south before the snow and ice set in." * 



The Mastodon {Mastodon Americanus), (Fig. 88), 

 " is probably the largest land mammal known, unless w T e 

 except the Dinotheriiim. It was twelve to thirteen feet 

 high, and, including the tusks, twenty-four to twenty-five 

 feet long. It differed from the elephant chiefly in the 

 character of its teeth. The difference is seen in Figs. 86 

 and 87. The elephant's tooth given above (Fig. 86) is 

 sixteen inches long, and the grinding surface eight inches 

 by four." 



The mastodon, together with the mammoth, made 

 their appearance about the middle of the Miocene epoch. 



* Lyell, Antiquity of Man, p. 180, 



