254 M. Boussingaulf s [Oct. 



clambering over a naked rock. We suffered much more in 

 scaling Cotopaxi than in ascending Chimborazo ; because, 

 on the former, we were constantly on snow. 



The Indians of Antisana also assured u& that they felt a 

 degree of stifling (ahogo) when they walked for a long time 

 on a snowy plain ; and, I confess, that on considering the in- 

 conveniences to which Saussure and his guides were exposed 

 while bivouacking on Mount Blanc, at the height of 3,888 

 metres (12,752 feet), I am disposed to attribute it, partly, 

 at least, to the unknown action of the snow. This point 

 was not so high as the towns of Calamarca and Potosi.^ 



On the lofty mountains of Peru, in the Andes of Quito, 

 travellers, and the mules which carry them, sometimes feel, 

 on a sudden, a very great difficulty in breathing, and fre- 

 quently the latter fall nearly into a state of asphyxia. This 

 occurrence is not constant, and in most cases appears to be 

 independent of the rarefaction of the air. It occurs princi- 

 pally when the mountains are deeply covered with snow, 

 and during the prevalence of a calm. It may be remarked 

 here, that Saussure was relieved from the disagreeable 

 feelings which attacked him on Mount Blanc whenever a 

 south-east wind blew. 



In America, this state of the air, which affects the organs 

 of respiration, is characterized by the name of soroche. 

 Soroche, in the language of the American miners, signifies 

 pyrites. Hence, they seem to attribute the cause of this 

 phenomenon to subterraneous exhalations. This is not 

 impossible, but the influence of the snow affords an easier 

 explanation. 



The feeling of suffocation which I have often experienced 

 while travelling over snow upon which the sun was shining, 

 I have been inclined to consider as induced by the vitiated 

 air which was disengaged from the snow by the action of 

 heat. 



This idea is supported by an experiment of Saussure, in 

 which he found that the air disengaged from snow contained 

 much less oxygen than that of the atmosphere. The air 



• According to M. Pentland, Calamarca is elevated 4,141 metres (13,582 feet.) 

 The highest part of the town of Potosi is 4,166 metres (13,664 feet). (The lieights 

 of the most elevated points of the Andes are according to the same authority ; 

 Sorate 25,400 feet ; lUimani 24,350 feet, and Chimborazo, 21 ,400 feet.— Edit.) 



