226 THE NOBLE SCIENCE, 



consisted of the vapours ascending from the earth during 

 the night-time, which, being condensed by the coldness 

 of the atmosphere, are prevented from being dissipated, 

 as in the day-time, by the sun's heat." 



We are told of other experiments, the result of 

 which " was quite conformable to his expectations." 



On the other hand, we find that " M. Mushenbrock, 

 who embraced the contrary opinion, thought he had in- 

 validated all Dr. Dufay's proofs, by repeating his expe- 

 riments, with the same success, on a plane covered with 

 sheet lead. But to this Dr. Dufay replied, that there 

 was no occasion for supposing the vapour to rise through 

 the lead, nor from that very spot ; but that, as it arose 

 from the adjoining open ground, the continual fluctu- 

 ation of the air could not but spread it abroad, and 

 carry it thither in its ascent." 



" Who shall decide, when doctors disagree V 



From the combination of all circumstances, which it 

 would be tedious to enumerate, not a doubt is left upon 

 my own mind, that the dew is an exhalation from the 

 earth, occasioned by the warmth of the sun. We see 

 little, if any, dew in cloudy weather ; but always the 

 most after the hottest days ; and, as a matter of course, 

 in the mornings preceding the hottest days, from the 

 accumulation through the night. The first appearance, 

 and the greatest collection of dew, is, invariably, observ- 

 able upon water-meadows, and on the surface of damp 

 ground most liable to such exhalation ; if it descended, 



