358 NORTHERN CHILE. (cHap. XVI. 
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 ofa 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 Indio-human period: but such small elevations could 
have had little power in deflecting the moisture-bringing atmos- 
pheric currents. Dr. Lund, however, found human skeletons 
in the caves of Brazil, the appearance 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 some- 
times 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-con- 
duits, 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 
* 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 population 
where now all is desolate.’ He makes similar remarks in another place; 
but I cannot tell whether this desolation has been caused by a want of popu- 
lation, or by an altered condition of the land. 
* 
