SIS POKTILLO PASS, lour.** 



the course of a few years, was discovered by a man who threw a 

 stone at his loaded donkey, and thinking that it was Aery heavv. 

 he picked it up, and found it full of pure silver * the vein occurred 

 at no great distance, standing up like a wedge of metal. The 

 miners, also, taking a crowbar with them, often wander on Sun- 

 davs over the mountains. In this south part of Chile, the men 

 who drive cattle into the Cordillera, and who frequent every 

 ravine where there is a little pasture, are the usual disco- 

 verers. 



20th. — As we ascended the valley, the vegetation, with the 

 exception of a few pretty alpine flowers, became exceedingly 

 scanty ; and of quadrupeds, birds, or insects, scarcely one could 

 be seen. The lofty mountains, their summits marked with a few 

 patches of snow, stood well separated from each other; the val- 

 leys being filled up with an immense thickness of stratified allu- 

 vium. The features in the scenery of the Andes which struck 

 me most, as contrasted with the other mountain chains with which 

 I am acquainted, were, — the flat fringes sometimes expanding 

 into narrow plains on each side of the valleys, — the bright co- 

 lours, chiefly red and purple, of the utterly bare and precipitous 

 hills of porphyry, — the grand and continuous wall-like dikes, — - 

 the plainly-divided strata which, where nearly vertical, formed 

 the picturesque and wild central pinnacles, but where less in- 

 clined, composed the great massive mountains on the outskirts 

 of the range, — and lastly, the smooth conical piles of fine and 

 brightly-coloured detritus, which sloped up at a high angle from 

 the base of the mountains, sometimes to a height of more than 

 2000 feet. 



I frequently observed, both in Tierra del Fuego and within 

 the Andes, that where the rock was covered during the greateT 

 part of the year with snow, it was shivered in a very extraordi- 

 nary manner^ into small angular fragments. Scoresby* has ob- 

 served the same fact in Spitzbergen. The ease appears to me 

 rather obscure : for that part of the mountain which is protected 

 by a mantle of snow, must be less subject to repeated and great 

 changes of* temperature than any other part. I have sometimes 

 thought, that the earth and fragments of stone on the surface, 

 were perhaps less effectually removed by slowly percolating shom * 

 * Scoresby *s Arctic Regions, vul. i. p. 122. 



