378 CHARLES DARWIN 



no passes, and where the land produces absolutely nothing, 

 and what is still more extraordinary, where there is no water. 

 Nevertheless it is the opinion of the people of the country 

 (although they are much puzzled by the circumstance), that, 

 from the appearance of the houses, the Indians must have 

 used them as places of residence. In this valley, at Punta 

 Gorda, the remains consisted of seven or eight square little 

 rooms, which were of a similar form with those at Tambillos, 

 but built chiefly of mud, which the present inhabitants can- 

 not, either here or, according to Ulloa, in Peru, imitate in 

 durability. They were situated in the most conspicuous and 

 defenceless position, at the bottom of the flat broad valley. 

 There was no water nearer than three or four leagues, and 

 that only in very small quantity, and bad : the soil was abso- 

 lutely sterile ; I looked in vain even for a lichen adhering to 

 the rocks. At the present day, with the advantage of beasts 

 of burden, a mine, unless it were very rich, could scarcely 

 be worked here with profit. Yet the Indians formerly chose 

 it as a place of residence ! If at the present time two or 

 three showers of rain were to fall annually, instead of one, 

 as now is the case during as many years, a small rill of water 

 would probably be formed in this great valley; and then, by 

 irrigation (which was formerly so well understood by the 

 Indians), the soil would easily be rendered sufficiently pro- 

 ductive to support a few families. 



I have convincing proofs that this part of the continent of 

 South America has been elevated near the coast at least from 

 400 to 500, and in some parts from 1000 to 1300 feet, since 

 the epoch of existing shells; and further inland the rise pos- 

 sibly may have been greater. As the peculiarly arid character 

 of the climate is evidently a consequence of the height of the 

 Cordillera, we may feel almost sure that before the later ele- 

 vations, the atmosphere could not have been so completely 

 drained of its moisture as it now is ; and as the rise has been 

 gradual, so would have been the change in climate. On this 

 notion of a change of climate since the buildings were 

 inhabited, the ruins must be of extreme antiquity, but I do 

 not think their preservation under the Chilian climate any 

 great difficulty. We must also admit on this notion (and 

 this perhaps is a greater difficulty) that man has inhabited 



