CORA SHEAR-TAIL HUMMING-BIRD. 255 



and glaciers, and avalanches ; and, indeed, all the 

 risks and perils of an Alpine country. 



Sometimes the valley traversed is barely wide 

 enough to allow the travellers to pass. It might 

 be called a narrow cleft between two perpen- 

 dicular rocks, that here and there nearly touch 

 each other. 



Masses of half-loosened rock threaten to fall 

 from the sides of the precipice every moment. 

 Nay, such a thing often takes place, and mules, 

 and even travellers, will be swept into the abyss. 



On these mountains, part of the grand range 

 of the Cordilleras, people are seized with faint- 

 ing, and a malady like sea-sickness. The height 

 above the level of the sea is ten thousand feet. 



Another disease often met with is blindness. 

 The brilliance of the sun on the dazzling white of 

 the snow has that effect ; and the utmost caution 

 is necessary to protect the eyes from the excessive 

 glare. 



Now and then, the traveller is overtaken by a 

 terrific storm of thunder and lightning. For 

 hours the flashes continue with awful brilliancy, 



