252 On Dr. Wells's Essay on Dew. [April, 



3. Even Dr. Young, tliough his Lectures on Natural Philosophy 

 prove him to have been well skilled in the new doctrine of heat, 

 has Hdvanced in that work an opinion upon the cause of dew, in the 

 most ordinary form of its occurrence, which has not the least con- 

 nection with any modern discovery, as 1 shall more particularly 

 mention hereafter. 



I might proceed in this way considerably fur her ; but what has 

 been said is. 1 think, sufficient to establish, that, when regard is 

 paid to the imperfection of the human understanding, my theory of 

 dew is not an obvious consequence of the recent doctrine of heat. 

 My explanation, indeed, of the immediate cause of dew is alto- 

 gether independent of that doctrine, beinj^ grounded on the simple 

 fact, that bodies ahvays become colder than the neighbouring air 

 before they are dewed, and was consequently open to the discovery 

 of every person since tlie invention of thermometers. It is true, 

 that the next step in my theory could not have been taken, without 

 the assistance of the late discoveries of others, and this has been 

 amply acknowledged in my Essay. 



II. " Dr. Wells," says Dr. Y., " appears, in his historical 

 account of the doctrines relating to the nature and causes of dew, 

 to have undertaken to atibrd us complete information respecting the 

 sentiments, not only of Aristotle and Theophrastus, but also of the 

 " most distinguished" philosophers of modern times: some of the 

 works, however, of the persons whom he mentions, and some of 

 the latest, have most unaccountably escaped his attention." In this 

 sentence there are two small mistakes, which, from my respect for 

 the author, I must suppose unintentional, though they give point 

 to his statement. The first relates to the engagement into which he 

 regards me to have entered concerning the opinions of preceding 

 writers on dew; for I never gave the slightest hint, that could lead 

 him to the conclusion which he has made. I knew that my account 

 of opinions on the cause of dew was incomplete ; and well it might 

 be, since the whole of it, with the accompanying refutations, does 

 not occupy more than three pages of my Essay. But my health, at 

 the time of its being drawn up, was in such a state, that I scarcely 

 hoped that I should ever finish my work, and my notes were so 

 written, that no person besides myself could make use of them. I 

 composed therefore in haste, and had neither leisure nor strength to 

 search public libraries for all the works, which I wished to consult. 

 I certainly thought, however, that what I had collected contained 

 every thing of much importance, which had been said upon my 

 subject. The second mistake consists in his applying the vvords 

 *' most distinguished," which were used by me concerning the 

 authors, who had given opinions on the formation of ice in India, 

 to those who had treated of dew. 



I pass now to more important matters. Dr. Y. in support of 

 what he has said respecting some veiy late and important works, 

 connected with my subject, having most unaccountably escaped my 

 attention, gives a long extract from the '^ Rccherches sur la Cha- 



