Mr. Harvey on the Formation of Mists. 55 



Art. VII. Experimental Inquiries relative to the For- 

 mation of Mists. By George Harvey, Esq., Mem- 

 ber of the Astronomical Society of London. 

 Many of the results contained in the following paper were 

 obtained in consequence of repeating the interesting experi- 

 ments on the temperature of air and water, performed by the 

 President of the Royal Society, during his continental tour, 

 and which he instituted with the view of tracing the causes 

 which contribute to the formation of mists over the beds of 

 rivers and lakes, in calm weather during the night, and an 

 account of which may be seen in the Philosophical Transactions 

 for 1819. 



It must not be understood, however, that this essay is sub- 

 mitted to the readers of the Journal of Science, with the slightest 

 idea that it can in any degree add to the unquestionable ac- 

 curacy of the principles on which Sir Humphrey Davy has 

 founded his theory ; and it is, therefore, hoped that it will 

 merely be regarded as a series of illustrative examples, which 

 the local facilities of Plymouth and its neighbourhood have 

 afforded for observations of this kind. These facilities arise 

 from the elevation of the land surrounding the water, and from 

 the depth of the river Tamer and of the sea ; both of which, 

 according to a remark of the above philosopher, are essential 

 conditions, in order to produce a mist of any considerable 

 density or magnitude. The present year afforded many oppor- 

 tunities for attending to this interesting subject, and in no case 

 have I perceived any phenomena at all at variance with the 

 principles laid down in the paper before quoted. 



As this paper, therefore, will contain little more than a re- 

 gister of facts, they will be detailed nearly in the order in which 

 they occurred, with the addition only of such observations as 

 may have a tendency to illustrate the phenomena with which 

 they are connected. 



Some experimental inquiries, relating to the deposition of 

 dew, rendered it necessary that the whole of the night of the 

 27th of April should be devoted to observations connected with 



