Electrical Conditions of the Atmosphere. 99 



altitude was still over two miles, and vegetation 

 extremely scant. Here the night was passed, in 

 a locality that, from the possibility of a heavy snow, 

 was extremely dangerous, a cave being the only re- 

 treat in case of a storm. There was scarcity of fuel, 

 and, owing to the altitude, it required four or five 

 hours to boil potatoes ; indeed, Darwin boiled his 

 two days, and found them as hard as at first. 



The electrical condition of the atmosphere was 

 very noticeable, as well as its transparency. In re- 

 ferring to this, he says : " 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 de- 

 gree 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 ap- 

 pearing to be brought nearly into one plane, as in a 

 drawing or panorama. The transparency is, I pre- 

 sume, owing to the equable and high state of atmos- 

 pheric 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 



