Steam Navigation in Britain. 245 



distant parts of the island, giving as it were life and activity to 

 the whole. 



If these facts are considered by you as worthy of a place in 

 your publication, they are much at your service ; and it is hoped 

 they may lead to further details on the same subject. 

 I am. 



Your obedient Servant, 



J. L. 



Art. VIII. On the Floatage of small heavy Bodies in Air, 

 and certain Atmospheric Phenomena dependant thereon. 

 By G. W. Jordan, Esq. F.R.S. Communicated by the 

 Author. 



Lamentable complaints and serious, if we may judge from 

 the characters of the persons making them, have been uttered 

 and published respecting the pernicious effects on the health of 

 the metropolis, produced by those dark volumes of smoke 

 which are seen to issue from the chimneys of large dimensions 

 and considerable altitudes, erected on the Surry side of the 

 Thames. The remedy proposed for these supposed evils has 

 been, to discover efficient methods of burning or consuming the 

 smoke, and to require of the manufacturers to use these me- 

 thods. These chimneys are by no means numerous in them- 

 selves, or as compared with the thousands of the metropolis ; 

 but their situation and their height expose them to observation, 

 and has excited alarms which further consideration might 

 have dispersed, or have induced a more ready acquiescence in 

 their toleration and use. When a charge of fresh coals is first 

 thrown on any one of these fires, a very dense black smoke is 

 seen to rise, whose particles are scarcely capable of floatage in 

 the atmosphere into which they are raised by the currents of 

 heated air passing up the chimneys. This dense smoke, how- 

 ever, soon changes, and changes successively its density and 

 colour, until it is scarcely visible. 1 have watched, and have 

 scarcely ever seen more than three or four of these chimneys at 

 one time discharging ihcir thick volumes of smoke, and even 



