April, 1835. ojos del agua. 413 



Mr. Gill mentioned to me a most interesting, and as far as 

 I am aware, quite unparalleled case, of the effect of sub- 

 terranean disturbances in altering 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 

 dr^'^ course of a considerable river, whence the water for irri- 

 gation 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 scattered, and in others the 

 solid rock had been worn into a broad channel.* It is self- 

 evident that a person following up the course of a stream, 

 win always ascend at a greater or less inclination. Mr. Gill 

 was therefore very much astonished, when walking up the 

 bed of this ancient river, to find himself suddenly going 

 dovm hill. He imagined that the slope had a fall of about 

 forty or fifty feet perpendicular. We here have the most 

 unequivocal evidence, that a ridge or line of hiUs has been 

 uplifted directly across the bed of a stream, which must have 

 been flowing for many centuries. From the moment the 

 river-course was thus arched, the water would necessarily be 

 thrown back ; and a new channel would be formed on one 

 side some way above. From that time, also, the neigh- 

 bouring plain would lose its fertilizing stream, and become 

 converted into the desert which it now remains. 



April 5th. — We had a long day's ride across the central 

 ridge, from the Inca's bridge to the Ojos del Agua, which 

 is situated near the lowest casucha on the western slope. 

 These casuchas are little round towers, with steps outside 

 to reach the floor, which is elevated some feet above the 

 ground on account of the snow-drifts. They are eight in 

 number; and under the Spanish government, were kept 



* Mr. Gill said he recollected that one part, which had been cut out 

 of the solid rock, was about forty yards wide and eight feet deep. This is 

 sufficient to give some idea of the size of the former stream. 



