Baron L. Von Buch on the Temperature of Springs. 167 



Von Buch remarks, Wahlenberg and also other philosophere 

 search for the cause of this phenomenon in the protecting cover of 

 snow, which, by reason of its feeble'conducting power of heat, 

 prevents the winter'scold sinking into the earth. This opinion rests 

 on the erroneous assumption, that the heat of the atmosphere 

 penetrates into the soil and subjacent rocks, by communication 

 through their mass. The observations of Saussure, by which it 

 was proved that heat did not penetrate to a greater depth than 

 thirty feet in the space of six months, shew how slowly such a mode 

 of distribution takes place ; and observations made afterwards in 

 a spring at Geneva, and continued for ten years, shewed, that, in 

 it, the minimum temperature occurred when the greatest heat pre- 

 vailed in the atmosphere, and the maximum at the time of the 

 greatest cold. We can scarcely believe that the cover of snow 

 would be sufficient to interrupt, during its long continuance of 

 several months, the radiation of the heat of the soil. Besides, 

 as the influence of two unequally heated bodies is always recipro- 

 cal, it follows, that, in the course of a year, even the best non- 

 conducting cover would not prevent the soil and rock from ac- 

 quiring the medium temperature of the atmosphere. 



It is also not easily understood how northern situations should 

 be more protected from such radiation than southern ones, when 

 it is known that the quantity of falling snow diminishes with the 

 increase of latitude ; and hence the snow-cover becomes less con- 

 siderable. We observe, with surprise, that Professor Leslie al- 

 so believes in this communication of heat through the soil, and 

 endeavours, but unsuccessfully, to adduce in favour of this opi- 

 nion, experiments made at Raith, with thermometers placed at 

 different depths in the soil. 



It is therefore necessary to repeat, continues Von Buch, how 

 this law is modified, and completely concealed by the agency of 

 a more active one ; namely, how this distribution can depend al- 

 most entirely on the infiltration of atmospheric water ^ by which 

 the temperature is distributed so quickly through the soil and 

 into the deep, that the immediate effect, by means of mere com- 

 munication, must be overcome at an inconsiderable depth, and 

 at length become completely insensible. 



Hence the great winter cold of the north acts so slightly on 

 the soil, and, with the greater difference, the lower the tempe- 



