238 DISSERTATION on the 



to become electric, than in any other ftate of the atmofphere ? 

 or, in other words, Why they become, in a more eminent de- 

 gree, ideo-electrie ? 



%dly, Air pofTeffes, like the other fluids we call menjlrua, the 

 power of difTolving different bodies, efpecially water, \*hich 

 laft procefs we term evaporation ; and, like the other menftrua, 

 this power is modified by the degree of heat it pofTeffes, fo 

 that, ceteris paribus, warm air can difTolve, and hold in folia- 

 tion, a much greater quantity of water than cold air. 



4-thIy, Suppose that air, heated to a given degree, holds in 

 folution as much water as it is able to difTolve, that is to fay, 

 that it is faturated with it, and it then cools down fo confi- 

 derably, that it cannot hold in folution the fame quantity it 

 did at firft ; there fhould, in that cafe, take place a large pre- 

 cipitation, or a large portion of the difTolved water fhould fe- 

 parate itfelf from the cooled air ; fo that it muft remain 

 charged with a much fmaller quantity than before it loft its 

 heat. 



$thly t It follows, then, that the atmofphere is never drier 

 than during great frofl, and never more humid than during 

 great heat ; and this affertion will appear a paradox only to thofe 

 who confound a dry with a drying air, and a wet with a wet- 

 ting air ; or who do not reflect that a dry air may not be of a 

 drying nature, and that a humid atmofphere may not be of a 

 wetting quality. I hope, likewife, nobody will maintain, that 

 the apparent purity, and perfect tranfparency of the air, in a 

 fine fummer day, is a proof of its not being charged with he- 

 terogeneous matter, as that tranfparency is only the effect of a 

 perfect folution of the water it contains. — It is evident, by the 

 common chemical operations, performed every day, that every 

 perfect folution is clear and tranfparent, and that when it be- 

 comes turbid, a precipitation is at hand. Let us confirm this 

 fact, Sir, by a phenomenon we have an opportunity of feeing 

 very often in fummer, viz. that we fhall find the air full of 



broken 



