312 TORTILLO PASS. tciiAi-. xv. 



under the shelter of some large fragments of rock. We met here 

 some passengers, who made anxious inquiries about the state of 

 the road. Shortly after it was dark the clouds suddenly cleared 

 away, and the effect was quite magical. The great mountains, 

 bright with the fall moon, seemed impending over us on all sides, 

 as over a deep crevice : one morning, very early, I witnessed the 

 same striking effect. As soon as the clouds were dispersed it froze 

 severely ; but as there was no wind, we slept very comfortably. 



The increased brilliancy of the moon and stars at this elevation, 

 owing to the perfect transparency of the atmosphere, was very 

 remarkable. Travellers having observed the difficulty of judging 

 heights and distances amidst lofty mountains, have generally 

 attributed it to the absence of objects of comparison. It appears 

 to me, that it is fully as much owing to the transparency of the air 

 confounding objects at different distances, and likewise partly to 

 the novelty of an unusual degree of fatigue arising from a little 

 exertion, habit being thus opposed to the evidence of the senses. 

 I am sure that this extreme clearness of the air gives a peculiar 

 character to the landscape, all objects appearing to be brought 

 nearly into one plane, as in a drawing or panorama. The trans- 

 parency is, I presume, owing to the equable and high state of 

 atmospheric dryness. 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 

 facility with which electricity is excited. My flannel waistcoat, 

 when rubbed in the dark, appeared as if it had been washed with 

 phosphorus ; every hair on a dog's back crackled ; even the linen 

 sheets, and leathern straps of the saddle, when handled, emitted 

 sparks. 



March 23rd. 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, 



