184 COSMOS. 



radius, the heat in the surface, cooled by radiation, would be 

 (according to Fourier's analytical theory) almost the same 

 as it now is in the upper crust of the earth. But if individ- 

 ual parts of the surface raise themselves in mountain chains 

 and narrow peaks, like rocks upon the bottom of the aerial 

 ocean, a diminution of heat takes place in the interior of the 

 elevated strata, and this is modified by contact with strata 

 of air of different temperature, by the capacity for heat and 

 conductive power of heterogeneous kinds of rocks, by the 

 sun's action on the forest-clad summits and declivities, by the 

 greater and less radiation of the mountains in accordance 

 with their form (relief), their massiveness, or their conical 

 and pyramidal narrowness. The special elevations of the 

 region of clouds, the snow and ice coverings at various ele- 

 vations of the snow line, and the frequency of the cool cur- 

 rents of air coming down the steep declivities at particular 

 times of the day, alter the effect of the terrestrial radiation. 

 In proportion as the towering cones of the summits become 

 cooled, a weak current of heat tending toward, but never 

 reaching an equilibrium, sets in from below upward. The 

 recognition of so many factors acting upon the vertical dis- 

 tribution of heat leads to well-founded presumptions regard- 

 ing the connection of complicated local phenomena, but not 

 to direct numerical determinations. In the mountain springs 

 (and the higher ones, being important to the chamois-hunt- 

 er, are carefully sought) there so often remains the doubt 

 that they are mixed with waters, which by sinking down in- 

 troduce the colder temperature of higher strata, or by ascer.d- 

 ing introduce the warmer temperature of lower strata. From 

 nineteen springs observed by Wahlenberg, Kamtz draws the 

 conclusion, that in the Alps we must rise from 9GO to 1023 

 feet in order to see the temperature of the springs sink 1 C. 

 (l-8 F.). A greater number of observations, selected with 

 more care by Hermann and Adolph Schlagintweit, in the 

 eastern Carinthian Alps and in the western Swiss Alps, on 

 the Monte Rosa, give only 767 feet. According to the great 

 work* of these excellent observers, " the decrease of the tem- 

 perature of springs is certainly somewhat more gradual than 

 that of the average annual temperature of the air, which in 

 the Alps amounts to about 320 feet for 1 F. The springs 

 there are, in general, warmer than the average temperature 

 of the air at the same level ; and the difference between the 

 temperature o'f the air and springs increases with the eleva- 

 * ^fonte 7To., 1853, cliap. vi., s. 212-225. 



