1835.] ^scent of Ckimhorazo. 47 



mirror. The atmosphere is remarkably pure, for, although 

 the snowy ridge appears covered with a cloud which seems 

 like smoke to emanate from it, yet it is merely a vapour, 

 which soon vanishing away, re-appears again, and is always 

 of an ephemeral nature. This formation of clouds at 

 intervals is a very frequent phenomenon on the tops of snowy 

 mountains. They appear principally in calms, and always 

 some hours after the culmination of the sun. In these 

 circumstances the glaciers may be compared to condensators, 

 pointing towards the upper regions of the atmosphere, which 

 serve to dry the air while cooling, and to return the water 

 to the surface of the earth, which is dissipated in the state 

 of vapour. 



These plateaus surrounded by glaciers, present sometimes 

 a most melancholy aspect, for when a continued wind brings 

 up the moist air from the hot regions, the mountains become 

 invisible, and the horizon is obscured by a line of clouds 

 which seem to touch the earth, and the day is cold and moist; 

 this mass of vapour being impervious to solar light. 



The twilight then is long. At other periods, as over the 

 equatorial zone, night succeeds the day quite suddenly; 

 the sun may be said to be extinguished in setting. 



I could not terminate my researches upon the trachytes 

 of the Cordilleras more properly than by a careful exami- 

 nation of Chimborazo. But what chiefly stimulated me to 

 pass the snowy limit, was the desire of obtaining the mean 

 temperature of a very elevated station. And although this 

 expectation was frustrated, my excursion, I hope, will not 

 be found devoid of utility to Science. 



I explain the reasons which induced me to ascend Chim- 

 borazo thus particularly, because I disapprove of dangerous 

 excursions on mountains, when they are not undertaken in 

 the cause of Science. For notwithstanding the numerous 

 ascents of Mount Blanc since the time of Suassure, he 

 appears to me the only one who attained its summit.* 



My friend Colonel Hall, who had already accompanied 

 me to Antisana and Cotopaxi, wished to join in the present 

 expedition, in order to increase the numerous facts which 



* Colonel Beaufoy, who ascertained the latitude on the summit of Mount Blane, 

 must certainly be separated from" the list of mere narrators of hair-breadth escapes. 

 See Ann. of Philosophy, ix. 97. — Edit. 



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