CLOSE OP POST-PLIOCENE ADVENT OP MAN. 285 



far less value than those of geology. In Britain 

 the age of iron is in the main historic. That of 

 bronze goes back to the times of early Phoenician 

 trade with the south of England. That of stone, 

 while locally extending far into the succeeding ages, 

 reaches back into an unknown antiquity, and is, as 

 we shall see in the sequel, probably divided into 

 two by a great physical change, though not in the 

 abrupt and arbitrary way sometimes assumed by 

 those who base their classification solely on the 

 rude or polished character of stone implements. 

 We must not forget, however, that in Western 

 Asia the ages of bronze and iron may have begun 

 two thousand years at least earlier than in Britain, 

 and that in some parts of America the Palaeolithic 

 age of chipped stone implements still continues. 

 We must also bear in mind that when the archae- 

 logist appeals to the geologist for aid, he thereby 

 leaves that kind of investigation in which dates are 

 settled by years, for that in which they are 

 marked merely by successive physical and organic 

 changes. 



Turning, then, to our familiar geological methods, 

 and confining ourselves mainly to the Northern 

 Hemisphere and to Western Europe, two pictures 

 present themselves to us : (!) The physical changes 

 preceding the advent of man ; (2) The decadence of 

 the land animals of the Post-pliocene age, and the 

 appearance of those of the modern. 



In the last chapter I had to introduce the reader 



