154 HEAT OF HIGHER LAYERS OF AIR. 



The limit of perpetual snow depends upon the 

 mean temperature of the ground, and especially 

 upon that of the summer months. The following 

 table shows the height of this snow-line on some 

 of the loftiest mountains which are well known to 

 us : 





H r— I i— I 00 



00 SO 

 t^OO 



o 10 



CO GO 

 GSZO 



O CO t* 

 + I + 



CM 00 



U5 CO 



fcj-fc*-«D i 



l|*H[Or-l|0«!tt TOl^ 



lO CM CM OS 



rji "^ Tjt CO 



O OlOOW- 



£ pL, a ct o 



ooooooooooooooo 



OOOOOQOOOOOOO^QO 



CM CO U3 00 GO o'co" lOr-T^T^r^O Co" 10 W 



•1 



