PERU. 255 
however, is far from being strictly true, except in certain parts of 
it. Were it not, however, for irrigation by the mountain streams, 
a great portion of Peru would certainly become nearly a desert. 
Indeed the upland is so now, not yielding any herbage whatever 
until the pasture region of the Cordilleras is reached. We are 
not to imagine, however, that the atmosphere is very clear, or that 
sunshine always prevails. It is extremely difficult to get a clear 
day. Father Feuillee has put upon record, more than a century 
ago, that the heavens were generally obscured. I can bear testimony 
to the truth of this remark, for although a glimpse of the sun was 
usually had some time during the day, yet it was almost as difficult 
to get equal altitudes at Callao during our stay as it was at Terra del 
Fuego. 
The dew (almozo) of Lima is never so great as to produce running 
water, yet it is more like rain than a Scotch mist. 
The peculiarity of their being no rain, has been accounted for in 
several ways, but not to me satisfactorily. The prevailing cold and 
dry winds from the southward sweep over the western shores of the 
continent; having a great capacity for moisture, they absorb it as 
they advance to the northward, from every thing ; on reaching the 
latitude of 12° S., they cease, and having become saturated, now rise 
to a sufficient height, where they are condensed by the cold strata, and 
again deposited on the mountains in almost constant rains. This will 
account for the aridity in the high Cordilleras of Chili, as well as for 
the existence of the desert of Atacama, and the want of rain on the 
coast of Upper Peru ; and at the same time, for the moisture of the 
high Cordilleras of Peru, which will be shortly spoken of. It will 
be remembered that our parties on the Cordilleras of Chili found the 
aridity to increase on ascending, to the very edge of the perpetual 
snow T , and all the plants were of a thorny character. 
The records of Lima mention the falling of rain only four times in 
the eighteenth century, and the occurrence of thunder and lightning 
an equal number of times. But this applies to a small part of Peru 
only, namely, the country bordering the coast, some fifty or sixty 
miles in width, around Lima. It will be seen that our party who 
visited the interior, w T hen at the height of ten thousand feet, entered 
a region subject to rain, and on the crest of the mountains the soil 
w r as kept perfectly moist by the frequent snows and rain. 
Mr. Bartlett, our Charge d'Affaires, gave me the range of the ther- 
mometer at Lima throughout the year, as being from 60° to 85° ; 
