I835-] RZD SNOW. 23S 



The snow was coloured only where it had thawed very rapidly, or had 

 been accidentally crushed. A little rubbed on paper gave it a faint 

 rose tinge mingled with a little brick-red. I afterwards scraped some 

 off the paper, and found that it consisted of groups of little spheres in 

 colourless cases, each the thousandth part of an inch in diameter. 



The wind on the crest of the Peuquenes, as just remarked, is generally 

 impetuous and very cold : it is said * to blow steadily from the west- 

 ward or Pacific side. As the observations have been chiefly made in 

 summer, this wind must be an upper and return current. The Peak of 

 Teneriffe, with a less elevation, and situated in lat. 28, in like manner 

 falls within an upper return stream. At first it appears rather surprising, 

 that the trade-wind along the northern parts of Chile and on the coast 

 of Peru, should blow in so very southerly a direction as it does ; but 

 when we reflect that the Cordillera, running in a north and south line, 

 intercepts, like a great wall, the entire depth of the lower atmospheric 

 current, we can easily see that the trade-wind must be drawn 

 northward, following the line of mountains, towards the equatorial 

 regions, and thus lose part of that easterly movement which it other- 

 wise would have gained from the earth's rotation. At Mendoza, on the 

 eastern foot of the Andes, the climate is said to be subject to long 

 calms, and to frequent though false appearances of gathering rain- 

 storms : we may imagine that the wind, which coming from the east- 

 ward is thus banked up by the line of mountains, would become 

 stagnant and irregular in its movements. 



Having crossed the Peuquenes, we descended into a mountainous 

 country, intermediate between the two main ranges, and then took up 

 our quarters for the night. We were now in the republic of Mendoza. 

 The elevation was probably not under 11,000 feet, and the vegetation 

 in consequence exceedingly scanty. The root of a small scrubby plant 

 served as fuel, but it made a miserable fire, and the wind was piercingly 

 cold. Being quite tired with my day's work, I made up my bed as 

 quickly as I could, and went to sleep. About midnight I observed the 

 sky became suddenly clouded : I awakened the arriero to know if there 

 was any danger of bad weather ; but he said that without thunder and 

 lightning there was no risk of a heavy snow-storm. The peril is 

 imminent, and the difficulty of subsequent escape great, to any one 

 overtaken by bad weather between the two ranges. A certain cave 

 offers the only place of refuge : Mr. Caldcleugh, who crossed on this 

 same day of the month, was detained there for some time by a heavy 

 fall of snow. Casuchas, or houses of refuge, have not been built in this 

 pass as in that of Uspallata, and therefore, during the autumn, the 

 Portillo is little frequented. I may here remark that within the main 

 Cordillera rain never falls, for during the summer the sky is cloudless, 

 and in winter snow-storms alone occur. 



At the place where we slept water necessarily boiled, from the 



diminished pressure of the atmosphere, at a lower temperature than it 



does in a less lofty country ; the case being the converse of that of a 



* Dr. Gillies in Journal of Natural and Geographical Science, Aug. 1830, 



This author <jives the heights of the Pa 



