viii RIVERS AND LAKES 289 



over, is perhaps the more interesting as being 

 evidently very recent. 



" Mr. Gill," he says, " mentioned to me a 

 most interesting, and as far as I am aware, 

 quite unparalleled case, of a subterranean dis- 

 turbance 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 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 chan- 

 nel, 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 



