412 PASSAGE OF COR&ILLERA. April, 1835. 



effect on the atmospheric moisture, and therefore on the 

 fertihty of the valleys in the upper Cordillera. From the 

 extreme slowness with which there is reason to believe the 

 continent is rising, the longevity of man as a species, 

 required to allow of sufficient change, is the most vahd 

 objection to the above speculations : for on the eastern 

 shores of this continent, we have seen that several animals, 

 belonging to the same class of mammalia with man, have 

 passed away, while the change of level between land and 

 water, in that part at least, has been so smaU, that it can 

 scarcely have caused any sensible difference in the climate. 

 I may add, however, that at Lima, the elevation, within the 

 human epoch, certainly has amounted to between seventy 

 and eighty feet. 



When at Lima, I conversed on this subject* 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 that con- 

 dition, by neglect and subterranean movements injuring 

 the water conduits, which the Indians formerly constructed 

 on so wonderful a scale. I may here just mention that 

 these people actually carried tunnels through hills of soUd 

 rock, when such were necessary to conduct the irrigating 

 streams. Mr. Gill told me, he had been employed pro- 

 fessionally 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 any 

 people should have attempted such operations without the 

 aid of iron or of gunpowder ! 



* 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- 

 lation where now all is desolate." He makes similar remarks in another 

 place, but it is not possible to judge, whether this desolation is owing 

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



