FOOD OF LARGF QUADRUPFDS 93 



many degrees beyond the limit where the ground at the 

 depth of a few feet remains perpetually congealed, are covered 

 by forests of large and tall trees. In a like manner, in Siberia, 

 we have woods of birch, fir, aspen, and larch, growing in a 

 latitude ^ (64°), where the mean temperature of the air falls 

 below the freezing point, and where the earth is so completely 

 frozen, that the carcass of an animal embedded in it is perfect!}' 

 preserved. With these facts we must grant, as far as quantity 

 alone of vegetation is concerned, that the great quadrupeds of 

 the later tertiary epochs might, in most parts of Northern Europe 

 and Asia, have lived on the spots where their remains are now 

 found. I do not here speak of the kind of vegetation necessary 

 for their support ; because, as there is evidence of ph\-sical 

 changes, and as the animals have become extinct, so may we 

 suppose that the species of plants have likewise been changed. 

 These remarks, I may be permitted to add, directly bear on 

 the case of the Siberian animals preserved in ice. The firm 

 conviction of the necessity of a vegetation possessing a 

 character of tropical luxuriance, to support such large animals, 

 and the impossibility of reconciling this with the proximity of 

 perpetual congelation, was one chief cause of the several 

 theories of sudden revolutions of climate, and of overwhelming 

 catastrophes, which were invented to account for their entomb- 

 ment. I am far from supposing that the climate has not 

 changed since the period when those animals lived, which now 

 lie buried in the ice. At present I only wish to show, that as 

 far as quantity of food alone is concerned, the ancient 

 rhinoceroses might have roamed over the steppes of central 

 Siberia (the northern parts probably being under water) even in 

 their present condition, as well as the living rhinoceroses and 

 elephants over the Karros of Southern Africa. 



I will now give an account of the habits of some of the 

 more interesting birds which are common on the wild plains of 

 Northern Patagonia ; and first for the largest, or South 



not penetrating above three feet, and at Bear Lake, in latitude 64°, not more than 

 twenty inches. The frozen substratum does not of itself destroy vegetation, for 

 forests flourish on the surface, at a distance from the coast." 



^ See Humboldt, Fragnuns Asiaiiqties, p. 386 ; Barton's Geography of Plants ; 

 and Make Brun. In the latter work it is said that the limit of the growth of trees in 

 Siberia may be drawn under the parallel of "jo" . 



