LINE OF PERPETUAL SNOW. 191 



capacity for heat that the upper regions of the 

 atmosphere are so intensely cold. Part of the 

 effect is likewise due to the loss by radiation into 

 space. This loss of temperature as we ascend 

 must be familiar to every visitor of mountain 

 scenery. Frequently it is picturesquely painted 

 by the snowy cap which envelops the summits 

 of the loftiest mountains ; and where the moun- 

 tains are of the most elevated description, at 

 a certain height there is a distinct line, visible 

 from afar, and forming a very peculiar feature 

 of landscape, which is well known as " the 

 line of perpetual snow." It is, in fact, in most 

 cases, an almost straight line between the fringe 

 of hardy and scanty vegetation, and a snowy 

 covering which clothes the mountains from its 

 summit to that point. This appearance suf- 

 ficiently indicates, by a sort of natural ther- 

 mometer, the temperature of the air at such 

 elevations. The line varies in height in dif- 

 ferent countries; and although highest in hot- 

 test countries, as at the equator, as a general 

 rule, and becoming lower as we approach the 

 poles, when it enters the earth, this law is by no 

 means without its exceptions, some of which are 

 of a very singular character. 



Of these exceptions, one of the most remark- 

 able that have recently presented themselves is 

 the account given by a missionary of a supposed 



