124 ACCOUNT OF THE ARCTIC REGIONS. 



dissolved, at the most considerable heights. The 

 higher Alps, excepting what is absolutely perpendi- 

 cular, remain const^-ntly covered with snow ; and 

 perhaps no instance of a thawing temperatiu-e ever 

 occurs on any of the most elevated summits. But, 

 in Spitzbergen, the frost relaxes in the months of 

 July and August, and a thawing temperature pre- 

 vails for considerable intervals on the greatest 

 heights which have been visited. IMartens ob- 

 serves, that in some of the countries of Europe, 

 when rain falls in the valleys, snow descends upon 

 the mountains, even in the height of summer ; but 

 that in Spitzbergen, rain falls on the tops of the 

 highest hills. 



As the capacity of air for heat increases as its 

 density decreases, and that in such a degree that 

 about every ninety yards of elevation in the lower 

 atmosphere produces a depression of one degree of 

 temperature of Fahrenheit, we find that the eleva- 

 tion of some of the Alps, Pyrenees, and mountains 

 of Nepaul, in the temperate zone, and of the Andes 

 and others in the torrid zone, is such, that their 

 summits are above the level where a temperature of 

 thawing can at any time prevail ; and though, by 

 the application of this principle to the mountains 

 of Spitzbergen, we find that a thawing temperature 

 may be occasionally expected ; yet we do not see how 

 t]ie prevalence of a thaw should be so continual as 



