244 OBSERVATIONS ON THE 



are more densely tenanted than those in the trunk of the river, where the 

 patches of soil for cultivation are dry, rocky and baked ; and the fields, 

 eaten away by the stream on one side, and hampered by the attrited 

 splinters of the cliffs, (which are constantly accumulating,) must in time 

 become extinct. This desolating influence, though slow, is irresistible, 

 and all the villages will eventually disappear under it, and the w^hole 

 shelf of the river be turned into a desert : the very cause which has 

 opened the country to the abode of mankind, will overwhelm it, and when 

 the mountains, from gradual abrasion, no longer bear any snow, the river 

 itself will be dried up. 



The tributary villages, or those not actually in the dell, are planted 

 high above and behind the terminal rocks upon a waving slope in the midst 

 of a black argillaceous soil, which from its open situation, is permanent. 

 The loftiest tenanted spots that have been barometrically determined, rest 

 at fourteen thousand seven hundred feet, and crops of beardless barley 

 extend to the verge of fifteen thousand. Men, animals, and vegetable 

 productions succeed better here than in the valley below, all thriving 

 profusely in a zone that contracts and terminates every trace of plants in 

 the Andes under the Equator ; nor is it at all improbable that the iiiterior 

 and flatter continuity of the country may nourish a cultivable soil in a 

 much loftier region, where increasing aridity and solar reverberation tend 

 to a higher limit of the Isothermal lines. At the extreme altitudes where 

 grain ripens in Spitt, the summer temperature, though considerable, is of 

 very short duration in an atmosphere where the heat dissipates so rapidly 

 that the nights are keen even in July ; hoar frost sometimes appearing 

 near the fields upon the highland and vallies of RupsM, where the 

 want of water for irrigation baffles all attempts at agriculture. It freezes 

 throughout the whole year, and so early as the middle of September, the 

 morning temperature was found between 13° and 17°, while in the day 

 time it reached to 58°. Upon the declivity of the SpiH valley, in the 



