256 On Dr. JFcUs's Essay on Dew. [April, 



1 had once intended to offer an explanation of some very curious 

 observations on dew by a Frencli autlior, Mr. B. Prevost, but that, 

 fearing to prove very tedious, 1 had afterwards given up the design. 

 1 intimated, however, tliat my explanation would have been, in 

 great measure, derived from the doctrine of radiant heat. On this 

 note Dr. Y. has remarked, that if I had been as solicitous to attend 

 to the labours of my contemporaries, as I had been laudably 

 anxious (the expressions are his) to recur to those of my prede- 

 cessors, I might have said, not that the experiments of Mr P. 

 might be easily explained, but that they actually had been explained 

 in a similar manner by one of my own countrymen, that is, by 

 himself. 



If Dr. Y. ascribes to me here a designed inattention to what he 

 has written upon Mr. P.'s experiments, he is very much in error; 

 but, if he means only, that, from want of sufficient diligence, I had 

 never read the explanation given of them in his Lectures, he is, I 

 believe, perfectly correct. For 1 do not recollect my havii^g seen 

 that explanation before I met with it in his Criticism, and I have no 

 note of it among my papers, though these contain a considerable 

 number of references to his 51st lecture, and one to the 6"0th. 

 The cause of my not having examined an intermediate one, which 

 contains the explanation spoken of, I take to be this, that having 

 gone to a public library, with the view of consulting his work, 

 while in haste, for the reason formerly mentioned, to finish ray 

 Essay, and not finding in the Index a single reference under the 

 word " Dew," to any of his lectures, I searched no further. 



But, admitting that I had been acquainted with Dr. Y.'s expla- 

 nation of Mr. P.'s experiments. I should not have been prevented 

 by that circumstance from offering one myself, if, from other 

 reasons, I had been inclined to do this ; since he treats of only a 

 part of those experiments, and leaves unanswered several important 

 questions relating to this part j whereas I should have treated of the 

 whole of them, and have attempted to answer aii the questions to 

 which they give rise. I proceed now to justify the opinion which I 

 have thus ventured to give respecting the inadequacy of Dr. Y.'s 

 explanation. In the prosecution of this undertaking, I shall, in 

 consequence of the indefinite manner in which the explanation is 

 expressed, endeavour to show from collateral circumstances what it 

 cannot be, rather than prove in a direct way what it is not. 



The experiments, considered by Dr. Y., comprise some of 

 the most important facts relating to the formation of dew ; he, 

 therefore, that can account for them fully, must, in my opinion, 

 possess the true theory of that appearance. But that this was not 

 the case with Dr. Y., when he jiublished his lectures, is proved by 

 the following passage in the very lecture, which contains the expla- 

 nation in question. " The dew, which is deposited upon vegetables, 

 is partly derived, in the evening, from the vapours ascending from 

 the lieated earth, [whence is the other part?] — and towards the 

 morning from t|ie moisture descending from the air atove, as it 

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