On a Carbonaceous Deposit or Film^ §fc, 27 



from the contemplation of this sublime work of nature, with- 

 out a glow of fervent admiration of the ** might, majesty, and 

 power " of nature's God. — The American Journal of Science 

 and ArtSy vol. xlvi. No. 1. January 1844, p. 67. 



On a Carbonaceous Deposit^ or Film, on the Lakes of West- 

 moreland. By JoHN Davy, M.D.,F.R.S., L. and E. Com- 

 municated by the Author. 



Although the lakes of "Westmoreland, in common with its 

 streams, are distinguished for the purity of their waters, yet 

 occasionally their surface may be seen covered to some extent 

 with a blackish film. I have observed such a film, or pellicle, 

 drifted, as it seemed, by the wind, when very gentle, not only 

 on Windermere, and the Rydal and Grasmere lakes, but also 

 on Easdale tarn, a small secluded mountain lake. 



The matter of this pellicle I have found, on examination, 

 to be chiefly carbonaceous, and very like the matter of soot 

 from coal : thus, it has deflagrated when heated with chlorate 

 of potash ; it has taken fire and consumed without flame be- 

 fore the blow-pipe ; triturated with water, so as to be tho- 

 roughly wetted, it has sunk ; and, under the microscope, it 

 has appeared to consist of particles of irregular form, varying 

 in size from ^^^^^ inch in diameter, or under that, to ^J^g 

 of an inch, or more ; and transmitting, like particles of soot, 

 a brownish light. 



Having the properties of soot, must it not be inferred that 

 the matter of this film is soot in reality, wafted probably from 

 a distance, from the great manufacturing districts of Lanca- 

 shire and Yorkshire, and brought down, when floating in the 

 atmosphere, by rain ; the mountains of the lake country act- 

 ing as great refrigeratories, tending to arrest and condense, 

 or precipitate, the vapours rising from lower and warmer 

 levels \ What is in favour of this view is, that the pellicle is 

 most commonly seen after heavy rains, succeeded by a calm 

 or a gentle breeze, and also that a similar matter is sometimes 

 observed on the surface of snow on the remote hills and 

 mountains. 



When it is considered to what vast distances the sand of 



