264 THE STORY OF THE EARTH AND MAN. 



valuable than the hard parts of animals. For in- 

 stance, the bones of elephants and rhinoceroses found 

 in Greenland would not prove a warm climate; 

 because the creatures might have been protected from 

 cold with hair like that of the musk-sheep, and they 

 might have had facilities for annual migrations like 

 the bisons. The occurrence of bones of reindeer in 

 France does not prove that its climate was like that of 

 Lapland ; but only that it was wooded, and that the 

 animals could rove at will to the hills and to the coast. 

 But, on the other hand, the remains of an evergreen 

 oak in Greenland constitute absolute proof of a warm 

 and equable climate ; and the occurrence of leaves of 

 the dwarf birch in France constitutes a proof of a cool 

 climate, worth more than that which can be derived 

 from the bones of millions of reindeer and musk-sheep. 

 Still further, in all those greater and more difficult 

 questions of geology which relate to the emergence 

 and submergence of land areas, and to the geographi- 

 cal conditions of past geological periods, the evidence 

 of plants, especially when rooted in place, is of far 

 more value than that of animals, though it has yet 

 been very little used. 



This digression prepares the way for the question : 

 Was the Miocene period on the whole a better age 

 of the world than that in which we live ? In some 

 respects it was. Obviously there was in the Northern 

 Hemisphere a vast surface of land under a mild and 

 equable climate, and clothed with a rich and varied 

 vegetation. Had we lived in the Miocene, we might 



