THERMAL SPRINGS. 191 



Tupac Yupanqui, upon the ridge of the Andes (Paso del 

 Assuay}, probably come from springs of the Lad era de Cad- 

 lud, where I have traced their course, near which the old 

 Peruvian causeway also ran, barometrically to an elevation 

 of 15,526 feet (almost that of Mont Blanc). 39 These are the 

 highest points at which I could observe spring water in 

 South America. In Europe the brothel's Schlagintweit 

 have found gallery-water in the gold mine in the Eastern 

 Alps at a height of 9442 feet, and found that the tempera- 

 ture of small springs near the opening of the gallery of only 

 33.4 F., 40 at a distance from any snow or glacier ice. The 

 highest limits of springs are very different according to geo- 

 graphical latitude, the elevation of the snow line and the rela- 

 tion of the hi^Uest peaks to the mountain ridges and plateaux. 

 If the radius of our planet were to be increased by the 

 height of the Himalaya at the Kintschindjun^a, and there- 

 fore uniformly over the whole surface by 28,175 feet (4.34 

 English miles), with this small increase of only -g-roth 

 of the 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 individual 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 narrow- 

 ness. The special elevations of the region of clouds, the 

 snow and ice-coverings at various elevations of the snow 

 line, and the frequency of the cool currents 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 



Hximboldt, Views of Nature, p. 393. 



40 Mine on the Great Fleuss in the Moll Valley of the Tauern, se 

 Hermann and Adolph Schlagintweit, Untersuchungen iOter die physifa- 

 liwhe Geographic 1#r Alzen, 1850, s. 242273. 



