MOUNTAIN MISTS. 217 



tall vegetation. There is a resistance to the wind 

 by friction, as it passes over these ; but the swell 

 of the air comes full and interrupted upon the 

 mountain, and as those temporales prove, the loss 

 of weight may be more than made up by increase 

 of velocity. 



There is also little doubt that the mountain 

 draws the atmosphere and the atmospheric mois- 

 ture towards it, notwithstanding that it is cold, 

 and that the general motion of the air on the sur- 

 face is toward the warm place. Over white snow, 

 the air, when the sun shines, is warm, very warm 

 as compared with that over a vast and black sur- 

 face at a much smaller elevation. Of course the 

 air ascends in consequence ; and the very snow 

 on the mountain has a self-maintaining property, 

 though it is continually refreshing the lower places 

 with springs and streams. 



But though the atmosphere over high mountains, 

 warmed as it is by the heat reflected from the 

 snow, raises moisture higher than the atmosphere 

 does over plains, yet it is less able, in cases of 

 change of temperature, to sustain that moisture. 

 If the mountain is so high that the air has only 

 half the density that it has at the mean level of the 

 earth, then the same volume of it will support only 

 half the weight whether of cloud or of any thing 

 else. Thus the very same texture of cloud which 

 is a fog over the city, or a creeping and even a dry 

 mist in the valley, may be a very wetting rain on 

 the mountain. Every one must know the saying 

 that " a Scotch mist will wet an Englishman to 

 the skin ;" and the fact is correct, both as to 

 Scotch and to all other mists, provided they be 

 mountain mists, and at a sufficient height. A 

 u 



