140 LINE OF PERPETUAL SNOW. 



grees, and once, at midnight, it rose to seventy- 

 three degrees, although in the shade at the same 

 time it was only thirty-six degrees. 



It has been already observed that, in conse- 

 quence of this powerful operation of the solar 

 rays upon surfaces at Spitzbergen which have 

 a favourable aspect and inclination, we find 

 mountains divested of their snowy covering at 

 elevations far above the line at which perpetual 

 frost may otherwise be presumed to exist. And 

 we shall be very much deceived if we suppose 

 the line of perpetual snow to ascend to the eleva- 

 tions at which we perceive this to take place ; 

 for while extensive tracts are sometimes seen 

 perfectly bare at the height of three thousand 

 feet, we at the same time find others in si- 

 tuations where the surface is nearly horizon- 

 tal, on which the snow remains hard at an 

 elevation of only fourteen hundred feet, as, for 

 example, upon the island of Amsterdam ; and we 

 should probably find it much lower if we could 

 meet with a surface similarly inclined at an in- 

 ferior elevation ; but upon this part of Spitz- 

 bergen plains of such a nature so rarely occur, 

 that we are very much limited in our obser- 

 vations. In very high latitudes during the sum- 

 mer solstice the sun is nearly perpendicular to 

 the surfaces of steep mountains for many hours 



