ULLOa's voyage to south AMERICA. ^89 



that in the time of the brifas in thofe climates where they are periodical, they blow 

 ftrongeft between the fetting and rifmg of the fun ; and this happening in September 

 and the following months, forms the fiimmer in Valles, when they enjoy clear days 

 and a lucid atmofphere. This was the cafe at Chocope at the time of that rain ; for, 

 though the inhabitants did not precifely mention the feafon in which that event happen- 

 ed, yet the feveral particulars related, efpecially that the fouth winds then prevailed 

 with an uncommon force, fufficiently indicate that it was in the fummer ; as this would 

 not have been at all remarkable in winter, when they are very variable and fometimes 

 ftormy. It may therefore be fafely concluded, that thefe events happened during the 

 fummer ; and, by way of corollary, that the brifas being flronger than ufual, and ad- 

 vancing fo far on the continent as even to reach the fouth winds, they were overpower- 

 ed by them, and Ihifted their point ; but the fucceeding fouth winds rendering it impof- 

 fible to return in the fame place, they left their former region, and blew in a current 

 nearer the earth. By which means, the vapours which had been exhaling during the 

 whole day, after being carried by the ftrongeft current of wind to a certain diftance, 

 afcended to the region where the brifas prevailed ; and being there repelled by them, 

 had time to condenfe ; for being within that region where the rain is formed, or where 

 many imperceptible drops compofe one of a large magnitude and gravity, and being more 

 minutely divided by the influence of the fun, they continued to afcend, till that power 

 ceafmg by the fetting of the fun, they again condenfed, and their weight becoming too 

 heavy to be fupported in the air, they defcended in rain, which was the more violent, 

 as the vapours were ftrongly repulfed by the brifas. At the dawn, thefe winds, as ufual, 

 began to decreafe, and the rain gradually leflened. The fouth winds blev/ all day as 

 before ; and there being then in the atmofphere no other winds to oppofe them, they^ 

 carried with them the vapours as they exhaled, and the atmofphere continued clear and 

 ferene. 



This happened at Chocope, fituated at a much greater diftance from the parts to 

 which the brifas extend than Tumbez, Piura, Sechura, and other towns where this is 

 more frequent, as being nearer the equinoQiial : notwithftanding, no brifas or north 

 winds are felt in that part of the atmofphere near the furface of the earth. So that it 

 is probable, or rather indeed evident from experience, that the north winds at the time 

 they prevail, more eafily reach to the countries neareft the equinoctial, than to thofe at 

 a greater diftance, though not fo as to be felt in the atmofphere near the earth, but in 

 a more elevated region. Confequently, it is natural for rains to be more frequent in 

 the former than in the latter, v^rhere thefe winds very feldom reach, whether in that 

 part of the atmofphere contiguous to the earth, or another, which being more diftant 

 from it they blow there more violently. 



I at firft declared againft any pofitive aflertion, that the opinion I have now laid 

 before the reader is founded on fuch undoubted phyfical principles, that no other can 

 be advanced more conformable to phenomena ; it being difficult immediately to fix on 

 caufes which agreeing with all circumftances, leaves the mind entirely fatisfied : and as 

 all within the reach of human perfpicuity cannot be accommodated to every particular, 

 as entire convidion requires, let it fuffice that I have here delivered my thoughts ; 

 leaving the naturalifts at full liberty to inveftigate the true caufe, and when difcovered^ 

 to reje6: my hypothefis. * 



* A more probable conjedlure is, that the vapours which arife in the great South Sea, and are brought 

 into this neighbourhood by the fouth wind (where they would naturally cofidenfe into clouds and fall 

 in fhowers), are attrafted by the "Cordilleras, whofe tops are generally enveloped in clouds frightful to 

 behold, which fpend themfelvesin tremendous tempefts, even ftiaking the foundations of thofe lofty moun- 

 tains. A. 



As 



