1-a-.] ELEVATION OF A RIVER-COURSE. 343 



existing shells; and further inland the rise possibly 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 elevations, 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 South 

 America for an immensely long period, inasmuch as any change 

 of climate effected by the elevation of the land must have been 

 extremely gradual. At Valparaiso, within the last 220 years, the 

 rise has been somewhat less than 19 feet : at Lima a sea-beach has 

 certainly been upheaved from 80 to 90 feet, within the Indo-human 

 period : but such small elevations could have had little power in 

 deflecting the moisture-bringing atmospheric currents. Dr. Lund, 

 however, found human skeletons in the caves of Brazil, the appear- 

 ance of which induced him to believe that the Indian race has 

 existed during a vast lapse of time in South America. 



When at Lima, I conversed on these subjects * with Mr. Gill, 

 a civil engineer, who had seen much of the interior country. He 

 told me that a conjecture of a change of climate had sometimes 

 crossed his mind; but that he thought that the greater portion of 

 land, now incapable of cultivation, but covered with Indian ruins, 

 had been reduced to this state by the water-conduits, which the 

 Indians formerly constructed on so wonderful a scale, having been 

 injured by neglect and by subterranean movements. I may here 

 mention, that the Peruvians actually 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 attempted such operations, without the use of iron or 



* Temple, in his travels through Upper Peru or Bolivia, in going 

 from Potosi to Oruro, says, " I saw many Indian villages or dwellings in 

 ruins up even to the very tops of the mountains, attesting a former 



popu aSLThere now all is desolate." He f*f/ m ^ *T 



is desolation has been 



another place; but I cannot tell whether this 



by a want of population, or by an altered condition of the land. 



