74 A VOYAGE TO Book VII. 



pcrses ilieni^ it proceeds from the increase of the 

 force of tlie winds during the winter, in a region 

 nearer the earth than in summer ; and the nearer the 

 lower part of this region is to the surface of the 

 earth, the nearer also will be the upper part; while, 

 on the contrary, in the summer, the higher the lower 

 part of tliis current of air is, the higher will be also 

 its upper part ; and, as we must suppose, with all 

 philosophers, that the vapours of the earth can ascend 

 only to that height, where the gravity of the parti- 

 cles of the vapours are equal to those of the air ; and 

 the rapidity of the wind extending in summer to 

 these limits, they are consequently involved in its 

 violent impulse ; and thence there cannot be such a 

 multitude of conglomerations as to form the mist 

 so common in winter ; for the winds in this season 

 sü'oíigiy blovring through a region nearer the earth, 

 the agitation in the upper parts is proportionally less. 

 And this current of air being below the region to 

 which vapours can ascend, the space intercepted be- 

 tween the upper part of this current, and the part 

 to which vapours rise, becomes filled with them. 

 All this seems natural, and is confirmed by expe- 

 rience ; for in winter the south winds are stronger 

 on the land than in summer. But as a further proof 

 may be thought necessary, I have added the fol- 

 lowing. 



ÍT has been said that in the town of Chocope, 

 two very hard and continual rains have happened ; 

 and that the same thing is more frequently seen at 

 Tumbez, and other town.s of those parts, after some 

 years of continual drought, which seems strange ; 

 for that being in the country of Valles, and not 

 at all dificrcnt from Lima, no rain would naturally 

 be expected there. Two causes for this, however, 

 liave occurred to me, one of them flowing from the 

 other. I shall begin with the first as productive of 

 the second. 



8 Frobí 



