Hot and Thermal Springs, Sfc. [257 



At what height do the yearly and daily variations of tempe- 

 rature cease ? During the above observations, the extent of 

 the variations of temperature were, 



In Zurich, . . • 12°.73 



And at the same time on Rigi Culm, 6°-90 

 Again at Zurich, • . 21° 58 



And at the same time at Geneva, 14°-92 

 And on the Faulhorn, . . 8°-50 



From this it indeed appears that the extent of the variations 

 of temperature is already considerably diminished in a difference 

 of height of 4203 feet, between Zurich and Rigi Culm, and in 

 6866 feet, between Zurich and the Faulhorn ; but we should 

 be drawing our conclusions too hastily were we to infer that 

 the point where the variations of temperature entirely disap- 

 pear cannot lie very high. The extent of these differences of 

 temperature does not only depend on the height, but also on 

 other causes, as is proved by the great difference between Zu- 

 rich and Geneva, which places are both at the same height 

 above the level of the sea. Even on the summits of the high- 

 est mountains in Switzerland variations of temperature are still 

 found. Thus, it sometimes rains on the top of Mont Blanc 

 during the hot summer months, and the snow sometimes begins 

 to melt there. Zumstein* observed a temperature of + 51°. 12, 

 on the 12th August 1819, on Mont Rosa, 13,920 feet above 

 the sea. Parrot-f* experienced an oppressive heat on the Lesa 

 glacier, on the southern side of the Rosa, at an elevation of 

 10,576 feet above the sea. Between the tropics, the point 

 where the variations of temperature cease, is probably not situa- 

 ted so high as in the temperate zones ; because, on the level of 

 the sea, the yearly and daily differences of temperature are 

 there confined within very narrow limits. However, Boussin- 

 gaultt relates that, on the 26th December 1831, a thermome- 

 ter, suspended free in the shade of a rock on Chimborazo, at a 

 height of 18,480 feet above the sea, and 3654 feet above the 

 limits of perennial snow, the greatest height to which moun- 

 tains have yet been ascended by men, and where the mean tem- 

 perature of the air is probably -f- 23°.0, shewed -f- 46°.04 ; and 



■ Gilbert's Annal., vol. C3. p. 391. 

 + Schweigger's Journ. xix., 386. 



J Poggendorfi's Ann. xxxiv., p. 206, and Edinburgh New Philosophical 

 Journal, vol. 19. p. 98. 



