1835.] ELEVATION OF A RIVER-COURSE. 359 



not most wonderful that men should have attempted such opera- 

 tions, without 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 

 cnanged 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 con- 

 ducted. There was nothing in the appearance of the water- 

 course, 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 40 yards in breadth and 

 8 feet deep. It is self-evident that a person following up the 

 course of a stream, will always ascend at a greater or less incli- 

 nation : Mr. Gill, therefore, was much astonished, when walk- 

 ing 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 40 or 50 feet perpendicular. We here have un- 

 equivocal 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 27th. We set out early in the morning, and by mid-day 

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

 with a little vegetation, and even a few algarroba trees, a kind of 

 mimosa. From having fire-wood, a smelting-furnace had for- 

 merly 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 ourselv es 

 warm. 



28th. 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 



24 



