462 JOUKNAL OF THE EOYAL HOBTICULTUKAL SOCIETY. 



Table I. 





oa 



Soot from same coal when burnt in 



Sitting-room 

 Grate 



Sample taken 



flit bfliSG of 



chimney 



Boiler Furnace 



Sample taken 

 70 feet above 

 base 



Sample taken 

 at top of 

 chimney 





Per cent. 



Per cent. 



Per cent. 



Per cent. 



Per cent. 



Carbon . 



69-30 



40-50 



16-66 



21-80 



27-00 



Hydrogen 



4-89 



4-37 



0-86 



1-44 



1-68 



Nitrogen 



1-39 



4-09 



0-00 



1-18 



1-21 



Ash 



8-48 



18-16 



75 04 



66-04 



61-80 



Tar 



1-64 



25-91 



0-09 



0-80 



1-66 



Sulphur 



1-74 



2-99 



2-07 



2-58 



2-84 



Chlorine 



0-27 



5-19 



0-11 



1-46 



1-60 



Free Acid 



0-00 



0-87 



1-33 



0-58 



0-56 



The analyses bring out very clearly the characteristic difference 

 between domestic soot and boiler soot — long familiar in connexion with the 

 use of soot as fertilizer— the boiler soot being far richer in ash and gritty 

 matter, and poorer in the valuable fertilizing ingredient, mtrogen, 

 than domestic soot. The figures for tar are of more immediate interest 

 for our present purpose, however, since the proportion of tar in soot 

 will largely determine the degree of permanency with which it will 

 adhere to leaves or other surfaces upon which it falls. It will be ob- 

 served that the domestic soot was far more tarry in character than the 

 boiler soot, and further analyses given in the same paper indicate that 

 the proportion of tar found in the former is by no means abnormal. In 

 one case, indeed, soot removed from the top of a domestic chimney 

 contained the extraordinary proportion of 40 per cent, of tarry matters. 



Further reference to the Table shows that soots contain appreciable 

 quantities of sulphur and chlorine, and that in most cases they have a 

 decidedly acid reaction, due to the presence in them of free acid, 

 probably sulphuric acid. The composition of soot thus suggests various 

 possibilities of damage to plants upon whose leaves or other feeding 

 area it may fall. 



Degree of Pollution of Atmosphebe in Different Parts of Leeds. 



In order to obtain information as to the nature and distribution of 

 the atmospheric impurities in and near Leeds, we collected samples of 

 rain in ten different quarters of the city throughout the twelve months 

 from November 1907 to October 1908, and determined the amounts of 

 suspended and dissolved impurities present in them. The samples were 

 collected by means of funnels 12 inches in diameter, which were left 

 permanently exposed, so that the rain collected would contain all the 

 impurities that fell and remained upon the funnel during the intervals 

 between successive showers. The results have been published in 

 extenso and discussed elsewhere.'*'' The following Table gives a summary 

 of them : — 



* Crowther and Buston, Journal of Agricultural Science, iv. 25. 



