12C On the Evening and Morning DelO, 



Afia, the Antilles, ami Mexico, and on board (hips which 

 navigate between the tropics, evening and morning dew havC 

 been obferved in fuch abundance, that bodies expofed to thoni 

 feemed as wet as if they had been drenched with rain. 



But a confcquence of very great importance, which I think 

 may be drawn from thefc phenomena, is, that they mud have 

 a great influence on the produftion and duration of the trade- 

 winds ; for the air of the torrid zone being excited to motion 

 almoft regularly every day, in two oppofite dircftions, by 

 forces very different in quantity, muft be impelled to aflume 

 and to prefcrve a movement in the diredion of the ftrongeft, 

 which is here the eaft wind, or that which brings with it 

 the dew of the morning. This caufe muft be more efleftual, 

 as it afts in the inferior part of the atmofphere, and as, by 

 affefting the denfeft part of the air, it is more capable of 

 eftablithino- a current in the whole mafs. 



Under tne frigid zone, where the fun, particularly during 

 Avinter, fcarcely rifes above the horizon in the courfe of the 

 whole day, the precipitation of water will be confiderable on 

 account of the coldnefs of the climate; the country will be 

 involved in a thick fog, which will be fcarcely difperfed on 

 the approach of fummcr; and when it takes place in funmier, 

 it will extend a great way into the temperate zone. Hence, 

 therefore, we obferve in our own country, during that feafon, 

 confiderable fogs, which are often fo thick as to fuffer only 

 a faint light to penetrate through them even at noon. 



It would be curious to exhibit here a feries of correal ob- 

 fervations on the circumftances which accompany the even- 

 ing and morning dew, at different times of the year, and in 

 different countries ; on the hour at which thefe phenomena 

 begin, and on the fufpcnfion or irregularity by which they 

 are affefted in different local fituationsj but if the generality 

 of the caufe to which they are here afcribed can excite the 

 attention of philofophers, the interefting tafk which I have 

 pointed out will no doubt be foon accomplifiied. 



IV. Procefs 



