ULLOA*S VOYAGE TO SOUTH AMERICA. 5B5 



The winds which prevail during the winter, are nearly, though not exactly, fouth ; 

 fometimes fhifting a little to the fouth-eaft between which and the fouth they always 

 blow. * This we obferved to have conilantly happened during the two winters we 

 fpent in this country, one at Lima, and the other at Callao ; the former in the year 

 1742, and the latter in 1743. The firft was one of the moft fevere that had been 

 felt, and the cold general in all that part of America to Cape Horn. In Chili, 

 Baldivia, and Chiloe, the cold was proportionable to the latitudes ; and at Lima it 

 occafioned conftipations and fluxions, which fwept away fuch numbers that it feemed 

 to refemble a peflilence. And though diforders of this kind are very common in the 

 winter feafon, they are rarely attended with the danger which then accompanied them. 



The extraordinary fingularity obferved in the kingdom of Peru, namely, that it 

 never rains ; or to fpeak more properly, that the clouds do not convert themfelves into 

 formal fhowers, has induced many naturalifts to enquire into the caufe : but in their 

 folutions of this difficulty they have varied, and invented feveral hypothefes to account 

 for fo ilrange an eiFeft. Some attribute it to the conftancy of the fouth winds, con- 

 cluding, that as they are inceflfant, they propel the vapours rifmg from the fea, to 

 the fame point ; and thus by never refling in any part, as no oppolite winds blow 

 during the whole year to check their courfe, there is not time fufficient for the mifts 

 to colle<El: themfelves, and, by an increafe of gravity, to defcend in the manner of 

 rain. Others have attributed it to the natural cold brought by the fouth winds, which 

 continue the atmofphere in a certain degree of heat during the whole year, and thus 

 increafe the magnitude of the particles of the air, which with the nitrous effluvia ac- 

 quired in its paflage over the furface of the fea, together with thofe of the feveral 

 minerals with which this country abounds, leflen its velocity, and confequently its 

 power of uniting the vapours fo as to form drops whofe gravity is greater than that 

 of the air. To this we may add, that the rays of the fun not exerting a force fuffi- 

 cient for uniting and putting them In motion, the heat being greatly leflened by the 

 coldnefs of the wind, the fog cannot be converted into drops of rain. For while the 

 weight of the cloud does not exceed that of the air, by which it is fupported, it cannot 

 precipitate. 



I (hall not cenfure this, or any other hypothefis, formed for explaining the above 

 phenomenon, not being certain that I have myfelf difcovered the true caufe ; I fhall 

 however give the reader my^ thoughts, and leave them to the difcuffion of philofophers. 

 In order to this I fhall lay down fome preliminary principles, which may ferve as a 

 foundation to thofe who fhall apply themfelves to difcover the true caufe of this pheno- 

 menon, with fome inflruftions for judging of the feveral hypothefes that have been 

 formed on this extraordinary fubjeft. 



I. It is to be fuppofed, that throughout the whole country of Valles, no other winds 

 are known during the whole year, than the foutherly, that is, between the fouth and 

 fouth-eaft, and this not only on the land, but alfo to a certain diftance at fea ; it evi- 

 dently appearing that the winds are limited between the fouth and fouth-eaft. It is 

 therefore very ftrange that fome writers fhould alTert that they are confined between 

 the fouth and fouth-weft, as this is abfolutely falfe. There are indeed intervals when 

 thefe winds are fcarcely felt, and an air, though extremely fmall, feems to come from 

 the north, and which forms the fog. 2. In winter the fouth wind blows harder than 

 in fummer, efpecially near the furface of the earth. 3. Though no formal rain is ever 



* The wind here blows fouth by caft to fouth by weft, but generally about fouth-fouth-eaft from June 

 to December. A. 



VOL. XIV. 4 F known 



