XVI ELEVATION OF A RIVER-COURSE 383 



have attempted such operations, 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 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 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 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 40 or 50 

 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 fertilising stream and become a desert. 



June 27///. — 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 firewood, 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. 



28///. — 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 Vicufia : 

 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. 



