42 DISCUSSIONS IN CLIMATOLOGY. 



tion the rays are not cut off; for the reflected rays are 

 of the same character as the incident rays which pass 

 so freely through the aqueous vapour. And in respect 

 to the remaining rays which are not reflected, but 

 absorbed by the snow, they do not manage to raise the 

 temperature of the snow above the freezing-point. 

 Consequently the air is kept in the condition most 

 favourable for the production of snow. 



Third. — ' Snow and ice lower the temperature by 

 chilling the air and condensing the vapour into thick 

 fogs. The great strength of the sun's rays during 

 summer, due to his nearness at that season, would, in 

 the first place, tend to produce an increased amount of 

 evaporation. But the presence of snow-clad mountains 

 and an icy sea would chill the atmosphere and condense 

 the vapour into thick fogs. The thick fogs and cloudy 

 sky would effectually prevent the sun's rays from 

 reaching the earth, and the snow in consequence would 

 remain unmelted during the entire summer.' 



On this Professor Newcomb's criticism is as follows: 

 — "Here he (Mr. Croll) says nothing about the latent 

 heat set free by the condensation, nor does he say 

 where the heat goes to which the air must lose 

 in order to be chilled. The task of arguing with a 

 disputant who in one breath maintains that the 

 transparency of the air is such that the rays reflected 

 from the snow pass freely into space, and in the next 

 breath that thick fogs effectually prevent the rays 

 ever reaching the snow at all, is not free from 

 embarrassment." 



If he really supposes my meaning to be that the air 

 is so transparent as to allow the incident and reflected 

 rays of the sun to pass freely without interruption 

 while at the same time and in the same place the air 

 is not transparent but filled with dense fogs which 



