120 NORTHERN CHILE. 



been injured by neglect and by subterranean move- 

 ments. ■ I may here mention that the Peruvians ac- 

 tually carried their irrigating streams in tunnels 

 through hills of solid rock. Mr. Gill told me he 

 had been employed professionally 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 at- 

 tempted such operations without the use of iron or 

 gunpowder 1 Mr. Gill also mentioned to me a most 

 interesting, and, as far as I am aware, quite unpar- 

 alleled 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 riv- 

 er, whence the water for iirigation had formerly 

 been conducted. There was nothing in the ap- 

 pearance of the water-course to indicate that the 

 river had not flowed there a few years previously ; 

 in some parts, beds of sand and gi'avel 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 unequiv- 

 ocal 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 



