324 KFFKCTS OF DRY ATMOSPHERE, [chap. xv. 



This dryness was shown by the manner in which woodwork 

 shrank (as I soon found by the trouble my geological 

 hammer gave me) ; by articles of food, such as bread and 

 sugar, becoming extremely hard ; and by the preservation 

 of the skin and parts of the flesh of the beasts which 

 had perished on the road. To the same cause we must 

 attribute the singular lacility with which electricity is ex- 

 cited. My flannel waistcoat, when rubbed in the dark, 

 appeared as if it had . been washed with phosphorus ; — 

 every hair on a dog's back cracked ; — even the linen sheets, 

 and leathern straps of the saddle, when handled, emitted 

 sparks. 



March 2yd. — The descent on the eastern side of the 

 Cordillera is much shorter or steeper than on the Pacific 

 side ; in other words, the mountains rise more abruptly from 

 the plains than from the alpine country of Chile. A level 

 and brilliantly white sea of clouds was stretched out beneath 

 our feet, shutting out the view of the equally level Pampas. 

 We soon entered the band of clouds, and did not again 

 emerge from it that day. About noon, finding pasture for 

 the animals and bushes for firewood at Los Arenales, we 

 stopped for the night. This was near the uppermost limit 

 of bushes, and the elevation, I suppose, was between seven 

 and eight thousand feet. 



I was much struck with the marked difference between 

 the vegetation of these eastern valleys and those on the 

 Chilian side ; yet the climate, as well as the kind of soil, is 

 nearly the same, and the difi"erence of longitude very trifling. 

 The same remark holds good with the quadrupeds, and in 

 a lesser degree with the birds and insects. I may instance 

 the mice, of which I obtained thirteen species on the shores 

 of the Atlantic, and five on the Pacific, and not one of them 

 is identical. We must except all those species, which 

 habitually or occasionally frequent elevated mountains ; 

 and certain birds, which range as far south as the Strait 

 of Magellan. This fact Is In perfect accordance with the 

 geological history of the Andes ; for these mountains have 

 existed as a great barrier, since the present races of animals 

 have appeared ; and therefore, unless we suppose the same 

 species to have been created in two different places, we 

 ought not to expect any closer similarity between the 

 organic beings on the opposite sides of the Andes than on 

 the opposite shores of the ocean. In both cases, w^e must 

 leave out of th« question those kinds which have been 



