189 



It is not the same with respect to the influence 

 exercised by the direction of the wind, and the 

 rapidity of the ascending current ; the latter 

 sometimes increases in an astonishing manner 

 the temperature of the loftiest mountains. I 

 have seen the thermometer rise, on the slope of 

 the volcano of Antisana, in the kingdom of Quito, 

 to 19°, when we were 2837 toises high. Mr. 

 Labillardiere * has seen it remain, on the edge 

 of the crater of the Peak of TenerifFe, at 18*7°, 

 though he had used every possible precaution to 

 avoid the effect of accidental causes. The tem- 

 perature of the road of Santa Cruz being then at 

 28°, the difference between the air of the coast 

 and on the summit of the Peak was 9*3°, instead 

 of 20°, which corresponds to a decrement of ca- 

 loric of 94 toises to each degree. I find in the 

 Journal of the Expedition of d'Entrecasteaux, 

 that at this period the wind at Santa Cruz was 

 south-south-east. This same wind blew perhaps 

 more impetuously in the higher regions of the 

 atmosphere, and forced back, in an oblique di- 

 rection, the hot air of the neighbouring conti- 

 nent toward the summit of the Piton. Besides, 

 the visit of Mr. Labillardiere took place on the 

 17th of October 1791 ; and, in the Alps of Swit- 

 zerland, we have observed, that the difference 

 of temperature between the mountains and the 



* Voyage a la Recherche de La Perouse, vol. i, p. 23; 

 vol. ii, p. 65. 



