128 ESSAY 



partly by observing on misty mornings copious 

 dews, which had been produced during preced- 

 ing clear nights. Respecting this point I can 

 aver, after much experience, that I never knew 

 dew to be abundant, except in serene weather. 

 In regard to the necessity of the air being still, 

 I know of no person who rejects it, except Mr. 

 Prieur*, a late French author of little con- 

 sideration, and he affirms, in opposition to the 

 most common observation, that a fresh wind is 

 requisite for the production of dew. 



The remark of Aristotle, however, is not to 

 be received in its strictest sense, as I have fre- 

 quently found a small quantity of dew on grass, 

 both on windy nights, if the sky was clear, or 

 nearly so, and on cloudy nights, if there was no 

 wind. If, indeed, the clouds were high, and 

 the weather calm, I have sometimes seen on 

 grass, though the sky was entirely hidden, no 

 very inconsiderable quantity of dew. Again ; 

 according to my observation, entire stillness of 

 the atmosphere is so far from being necessary 

 for the formation of this fluid, that its quantity 

 has seemed to me to be increased, by a very 

 gentle motion in the air. Dew, however, has 

 never been seen by me, on nights both cloudy 

 and windy. 



* Journal de 1'Ecole Poly technique, Tom. ii. 409. 



