266 



dered and barren pumice stone of the Piton 3 

 which impede the migration of the plants toward 

 the brink of the crater. 



Nevada of Grenada, the Pico de Veleta, the absolute height 

 of which is 1781 toises, is perpetually covered with snows : 

 but the inferior limits of these snows not having been mea- 

 sured, this mountain, in the latitude of 37° 10', gives us no 

 information respecting the problem we wish to solve. With 

 respect to the position of the volcano of TenerifFe, in the cen- 

 tre of an island of little extent, it does not appear, that this 

 circumstance can cause a rising of the curve of the perpetual 

 snows. If in islands the winters are less rigorous, the sum- 

 mers are less scorching 5 and it is not so much on the mean 

 temperature of the whole year, as on that of the summer 

 months, that the height of the snows depends. On Etna the 

 snows begin at 1500 toises, and even a little below 5 which is 

 extraordinary enough for a summit placed in 37 degrees and 

 a half of latitude. 



Towards the polar circle, where the heats of summer are 

 tempered by the fogs that rise continually above the Ocean, 

 the difference between the islands on the coasts and the in- 

 terior of the country becomes extremely perceptible. In 

 Iceland, for example, on the Osterjoeckull, in the sixty-fifth 

 degree of latitude, the perpetual snows descend to four hun- 

 dred and eighty two toises ; while in Norway, in the sixty- 

 seventh, far from the coasts, in situations where the winters 

 are much more rigorous, and where consequently the mean 

 temperature of the year is less than in Iceland, the snows de- 

 scend only to six hundred toises of height (Leopold von Buck, 

 in the Ann. of Gilb. 1812, t. ii, p. 37 and 43). From these 

 considerations it appears probable enough, that Bouguer and 

 Saussure were deceived, when they admitted, that the Peak 

 of Teneriffe reaches the constant inferior limit of the snows 

 (Figure de la terre, p. 48, and Voy, dans lesAlpes, t. iv, p. 103). 



