218 A BOOK-LOVER'S HOLIDAYS 



hundreds of thousands of years, in Europe. 

 During this period of time — immense by his- 

 toric standards, yet geologically a mere mo- 

 ment — many different human types succeeded 

 one another. The climate swung to and from 

 glacial to subtropical; fauna succeeded fauna. 

 One group of species of big beasts succeeded 

 another as the climate and plant life changed; 

 and then itself gave place to a third; and per- 

 haps once more resumed its ancient place 

 as the physical conditions again became what 

 they once had been. At certain periods the 

 musk-ox, the reindeer, the woolly rhinoceros, 

 and the hairy mammoth, together with huge 

 cave-bears, were found; at other periods south- 

 ern forms of elephant and rhinoceros, and 

 such tropical creatures as the hippopotamus, 

 replaced the beasts of the snow land. Horses 

 of different species were sometimes present in 

 incredible numbers. There were species of 

 wild cattle, including the European bison, and 

 the urus or aurochs — spoken of by Csesar, 

 and kin to, and doubtless partly ancestral to, 

 the tame ox. The cave-lion, perhaps indis- 

 tinguishable from the modern African lion, was 

 the most formidable beast of prey. I say *' per- 

 haps" indistinguishable, for we cannot be quite 

 certain. Some of the races of cave-dwelling 



