GREAT DRY COLD ON HIGH MOUNTAINS. 301 



has been already discussed in some detail. Mr. Darwin 

 first drew attention to it, with reference to the dry 

 sandy wastes of South Africa; and it is not a little 

 remarkable to find the same thing recurring in a 

 region of arctic cold, such as Thibet. The climate of 

 the latter, it must be observed, though one of intense 

 cold, is also exceedingly dry. Indeed " wherever these 

 extremes of heat and cold occur, the air is always 

 and of necessity extremely dry. " * We have also 

 already pointed out the remarkable similarity between 

 many of the circumstances which accompany great 

 dry heat, and great dry cold; and it is again to be 

 noted in this occurrence of great herds of game in 

 exceedingly dry and barren plains, in one case (as in 

 Africa) where the solar heats are intense, and in an- 

 other (as upon the lofty table-lands of Thibet) where 

 the piercing nature of the cold is no less equally 

 intense. Yet in both these cases, the game assemble 

 in these inhospitable wastes in extraordinary numbers, 

 though it would apparently seem that the means of 

 subsistence are by no means adequate to the main- 

 tenance of such a numerous stock of grazing animals. 



Thus Captain Hamilton Bower, speaking of the 

 great game herds of the Thibetan table-lands, ex- 

 presses his unfeigned surprise at their being able to 

 obtain the means of existence in these exceedingly 

 barren plains, and says, 



" The grasses, of which 23 species were collected, must be 

 extremely nourishing, as travelling across the plateaux, the 

 enormous herds of yak and antelope to be seen appear 

 quite disproportionate to 'the amount of grass to support 



* See Heat a Mode of Motion, by Professor J. Tyndall, 5th edit. 

 1875, pp. 35 2 53- 



