i3S.] ELEVATION OF A RIVER-COURSE. a6i 



Peruvians actually carried their irrigating streams in tunnels through 

 hills of solid rock. Mr. Gill told me, he had been employed profes- 

 sionally to examine one ; he found the passage low, narrow, crooked, 

 and not of uniform breadth, but of very considerable length. Is it not 

 most wonderful that men should have attempted such operations, with- 

 out the use of iron or gunpowder ? Mr. Gill also mentioned to me a 

 most interesting, and, as far as I am aware, quite unparalleled case, of 

 a subterranean disturbance having changed the drainage of a country. 

 Travelling from Casma to Huaraz (not very far distant from Lima), he 

 found a plain covered with ruins and marks of ancient cultivation, but 

 now quite barren. Near it was the dry course of a considerable river, 

 whence the water for irrigation had formerly been conducted. There 

 was nothing in the appearance of the watercourse to indicate that the 

 river had not flowed there a few years previously ; in some parts, beds 

 of sand and gravel were spread out ; in others, the solid rock had been 

 worn into a broad channel, which in one spot was about forty yards in 

 breadth and eight feet deep. It is self-evident that a person following 

 up the course of a stream will always ascend at a greater or less 

 inclination : Mr. Gill, therefore, was much astonished, when walking up 

 the bed of this ancient river, to find himself suddenly going down hill. 

 He imagined that the downward slope had a fall of about forty or fifty 

 feet perpendicular. We here have unequivocal evidence that a ridge had 

 been uplifted right across the old bed of a stream. From the moment 

 the river-course was thus arched, the water must necessarily have been 

 thrown back, and a new channel formed. From that moment, also, the 

 neighbouring plain must have lost its fertilizing stream, and become a 

 desert. 



June zjth. We set out early in the morning, and by midday 

 reached the ravine of Paypote, where there is a tiny rill of water, with 

 little vegetation, and even a few algarroba trees, a kind of mimosa. 

 From having fire-wood, a smelting-furnace had formerly been built 

 here : we found a solitary man in charge of it, whose sole employment 

 was hunting guanacos. At night it froze sharply; but having plenty 

 of wood for our fire, we kept ourselves warm. 



June zSth. We continued gradually ascending, and the valley now 

 changed into a ravine. During the day we saw several guanacos, and 

 the track of the closely-allied species, the Vicuna : this latter animal is 

 pre-eminently alpine in its habits ; it seldom descends much below the 

 limit of perpetual snow, and therefore haunts even a more lofty and 

 sterile situation than the guanaco. The only other animal which we 

 saw in any number was a small fox : I suppose this animal preys on 

 the mice and other small rodents, which, as long as there is the least 

 vegetation, subsist in considerable numbers in very desert places. la 

 Patagonia, even on the borders of the salinas, where a drop of fresh 

 water can never be found, excepting dew, these little animals swarm. 

 Next to lizards, mice appear to be able to support existence on the 

 smallest and driest portions of the earth, even on islets in the midst 

 of great oceans. 



