c8Q ULLOa's voyage to south AMERICA. 



decreafed, and great numbers of them being united, form that lofty mift which is feen 

 after the cloud is totally diflipated. This mift cannot be converted into rain ; for, hav- 

 ing paffed above the region proper for its formation, all the parts become congealed, 

 and their weight can never be increafed fufficiently to overcome the refiftance of the 

 air which fupports them ; for the quantity of thofe which have overcome this obftacle 

 being inconfiderable, they cannot be united with a fufficient quantity of others to with- 

 ftand the continual diffipation occafioned by the adlion of the rays of the fun. Nor 

 can they defcend in either fnow or hail, as might be expeded from their prefent ftate. 

 Befides following always, though with lefs velocity, the current of the wind, any fuch 

 concretion of them as to form a thick cloud is prevented : for, as we have already ob- 

 ferved, thefe mifts are fo tenuious, as to afford in the day-time a confufed view of the 

 dilk of the fun, and of the ftars in the night. 



In order to render the premifes agreeable to obfervation, one difficulty ftill remains, 

 namely, that thefe lofty mifts are feen only in winter, and not in fummer. But this, 

 in my opinion, muft naturally be the confequence ; for, befides the general reafon, 

 that the ftronger influence of the rays of the fun difperfes them, it proceeds from the 

 increafe of the force of the winds during the winter, in a region nearer the earth than 

 in fummer ; and the nearer the lower part of this region is to the furface of the earth, 

 the nearer alfo will be the upper part ; while, on the contrary, in the fummer, the 

 higher the lower part of this current of air is, the higher will be alfo its upper part ; 

 and. as we muft fuppofe, with all philofophers, that the vapours of the earth dan 

 afcend only to that height, where the gravity of the particles of the vapours are equal : 

 to thofe of the air ; and the rapidity of the wind extending in fummer to thefe limits, 

 they are confequently involved in its violent impulfe ; and thence there cannot be fuch 

 a multitude of conglomerations as to form the mift fo common in winter ; for the winds 

 in this feafon ftrongly blowing through a region nearer the earth, the agitation in the 

 upper parts is proportionally lefs. And this current of air being below the region to 

 which vapours can afcend, the fpace intercepted between the upper part of this current 

 and the part to which vapours rife, becomes filled with them. All this feems natural, 

 and is confirmed by experience ; for, in winter, the fouth winds are ftronger on the 

 land than in fummer. But as a further proof may be thought neceffary, I have added . 

 the following: 



It has been faid that, in the town of Chocope, two very hard and continual rains 

 have happened ; and that the fame thing is more frequently feen at Tumbez, and other 

 towns of thofe parts, after fome years of continual drought, which feems ftrange ; for 

 that being in the country of Valles, and not at all different from Lima, no rain would 

 naturally be expeded there. Two caufes for this, however, have occurred to me, one 

 of them flowing from the other. I fhall begin with the firft as produdive of the 

 fecond. 



From what has been faid, it may be inferred, that in a country or climate, where 

 one and the fame wind perpetually prevails, there can be no formal rain ; and, in order 

 to form it, either the wind muft entirely ceafe, or an oppofite wind muft arife, which, 

 by, checking the courfe of the vapours, brings them into contaft with thofe lately ex- 

 haled from the earth, and caufes them to condenfe in proportion as they rife by the 

 attraction of the fun, till being rendered heavier than the air by which they were fup- 

 ported, they defcend in drops of water. 



On reconfidering the circumftances of what happened at Chocope, it will appear, that 

 during the whole day, the Iky was clear, and that it was not before five in the evening 

 that the rain began, and with it the violence of the wind. It fhould alfo be obferved, 



that 



