PROCEEDINGS 



OF 



THE ROYAL SOCIETY. 



1837—1838. No. 31. 



December 7, 1837. 



FRANCIS BAILY, Esq.. Vice-President and Treasurer, 

 in the Chair. 



No paper was read. 



December 14, 1837. 

 JOHN GEORGE CHILDREN, Esq., Vice-President, in the Chair. 



The reading of a paper, entitled " On low Fogs and stationary- 

 Clouds." By William Kelly, M.D. Communicated by Captain 

 Beaufort, R.N., F.R-S., &c., was resumed and concluded. 



The object of the present paper is to point out the circumstances 

 which influence the formation of low fogs, and to show what ana- 

 logy exists between the causes that produce them and those that 

 occasion certain forms of clouds, which may be considered as differ- 

 ing from fogs only in position. Having been attached for several 

 years to the naval party employed in the survey of the gulf and river 

 of St. Lawrence, the author had ample opportunities of observing the 

 phenomena in question. He concludes that the fogs described oc- 

 cur chiefly when the air is nearly saturated with moisture, and when 

 at the same time the temperature of the water on which they rest 

 either exceeds that of the air, or is considerably below it. These 

 fogs are generally very dense, often limiting the sphere of vision to 

 a few fathoms ; but seldom extend to any considerable height. 

 They do not often cover the land to any distance from the shore ; 

 and the tops of the hills, close to the water's edge, are clear, while 

 the bases, or sides, are enveloped in the mist. 



The following papers were then read : — 



" On the Colours of Mixed Plates/' By Sir David Brewster, 

 K.G.H., F.R.S., &c. 



• In the prosecution of his optical inquiries, the author was induced 

 to study the phenomena of mixed plates, (originally discovered by 

 Dr. Young, and described by him in the Philosophical Transactions 

 for 1802,) as he had observed similar appearances in various mineral 

 bodies under analogous circumstances, to which he had been led to 



