﻿Manchester Memoirs, Vol. xlix. (1905), No. 14 9 



sition of Manchester soot is mure complicated than is 

 usually imagined. The cause of one of its most charac- 

 teristic properties, viz., its disagreeable smell, I was unable 

 to trace. It has been ascribed to pyridine bases, but I do 

 not know on what experimental basis this assumption is 

 made. Certain it is that it pervaded all the various 

 products which were isolated and is even possessed by the 

 recrystallised, colourless hydrocarbon which was obtained 

 from the benzene extract. To my mind, the smell is 

 more akin to humus or to the peculiar odour which is 

 given off from the earth when a shower of rain falls after 

 a period of dry weather, than to that of pyridine. It 

 would be interesting if one could ascertain what propor- 

 tion of the solid matter contained in smoke is retained 

 by the walls of the chimney as soot, and what pro- 

 portion enters the atmosphere. This would of course 

 depend largely on the conditions, such as quality of 

 coal, construction of the hearth or grate, length and 

 width of stack, and to a certain extent whether the 

 chimney had been recently swept or not. In any case, 

 however, I should be inclined to say that in a household 

 fire by far the greater portion of the solid particles enters 

 the atmosphere, and that the accumulated soot conse- 

 quently only represents a comparatively small proportion 

 of the separated matter. When high winds prevail, the 

 smoke in the city is carried away so rapidly that its 

 presence is not felt, but with a still atmosphere or a gentle 

 air it falls to the ground, where its presence is best 

 revealed by the appearance of snow which has been lying 

 for some days. Though this is blackest in the city itself, 

 its colour shows that deposition takes place for many 

 miles round Manchester, and it cannot but be that this 

 deposition must exert some influence on plant life. With 

 a clayey or sandy soil, which is not manured or limed. 



