52 ' M. Boussingaulfs [July 



we arrived at the foot of a wall of trachyte surmounted by 

 a peak which was several hundred metres in height. 



This was discouraging, although the barometer only 

 indicated an elevation of 5680 metres (18,630 feet). This 

 height was not great for us, because it was inferior to that 

 which we had reached on Cotopaxi. Humboldt had 

 ascended higher on Chimborazo, and we were anxious at 

 least to reach the station which that distinguished traveller 

 had attained. Mountain travellers, when discouraged, are 

 very apt to sit down, a plan which we followed at Pena 

 Colorada (red rock). This was the first time we had in- 

 dulged ourselves with a seat. We felt extremely thirsty, 

 and were first occupied in sucking the ice to quench our 

 thirst. It was three-quarters past noon, and yet we felt 

 very cold. The thermometer having sunk to 0°-4 (32^°). 

 We were enveloped in a cloud ; the hair hygrometer stood 

 at 91 J°. The vapour disappeared and the hygrometer re- 

 mained at 84°. 



So much moisture may appear extraordinary at such a 

 height, but it constantly occurs among the glaciers of the 

 Andes, and appears to admit of a very natural explanation. 

 During the day the surface of the snow is generally moist ; 

 the rock of Pena Colorada, for example, was all wet. 

 Hence, the air near the glacier must then be saturated with 

 moisture. On Mount Blanc, Saussure found the hygro- 

 meter at 59° and 51°, the temperature varying from 0*5 to ■ 

 — 2°3 R. (33°1 to 26°-82 F.) 



Now, it is not uncommon to observe at the same level of 

 the sea a similar hygrometrical state of the atmosphere. 

 In the Cordilleras great dryness is experienced at 2000 

 and 3500 metres (7,560, 11,480 feet). At Quito and Santa 

 Fe de Bogota, we have seen, as I have noticed in another 

 place, the hygrometer of Saussure descend to 26°.* The 

 accidents which persons frequenting the glaciers have ex- 

 perienced, especially the very frequent alteration of the skin 

 of the face, cannot be ascribed, therefore, to the acid nature 

 of the air. This change appears to me attributable to the 

 action of strong light, since to protect the skin from chop- 

 ping, it is sufiicient to cover the face with a simple coloured 



* Researches into the cause of Goitre. Ann. de Chemie et do Physique. 



