E. J. Russell and E. H. Richards 319 



activity in the soil is at a miniimini ; and highest in June, July, August 

 and October, when biochemical activity in the soil is at a maximum. 

 The other source with which the atmosphere may be in equilibrium 

 is the atmosphere of cities, where the amount of ammonia is markedly 

 greater than in the country. The amount of ammonia brought down 

 by the rain of certain towns is as follows, the Rothamsted and Malvern 

 figures for the same periods being given for purposes of comparison: 



Nitrogen as ammonia in lliti. per acre per anniim^. 



If the whole of the ammonia were carried down in the rain there 

 woidd of course be none to travel out into the country, but as pollution 

 is constantly going (in there may be an excess during the intervening 

 dry periods. It is not certain, however, that atmospheric pollution 

 would be sufficient by itself to account for all the ammonia present in the 

 rain. The value obtained at Rothamsted is not likely to be higher, indeed 

 it is probably lower, than the average over Great Britain: assuming 

 only 2-6 lb. per acre the total amount of ammonia brought down on 

 the 56,000,000 acres of Great Britain would be 65,000 tons of combined 

 nitrogen, equivalent to 325,000 tons of sulphate of ammonia per 

 annum^. The total coal consumption of the country is approximately 

 200,000,000 tons per annum: if all this were handled at gas works or 

 in coke ovens it would yield some 2,000,000 tons of sulphate of ammonia, 

 assuming 22-7 lb. sulphate of ammonia were obtained from each ton 

 of coal. But the open grate is far less efficient as a producer of ammonia 

 than the gas retort, and nothing approaching this quantity is likely 

 to arise. Of the amount actually formed no less than 400,000 tons 

 is collected from gas and recovery plants, and a further large quantity 

 is absorbed in soot. The amount discharged into the atmosphere is 

 the diSerence between these quantities and the total production: it is 

 impossible to make a satisfactory estimate, but there seems hardly 

 enough left to furnish even the 325,000 tons of sulphate of ammonia, 



' Taken from reports of Advisory Committee on Atmospheric Pollution. 



^ This figure is rather interesting: it is nearly 900 tons per day, and is considerably 

 more than the whole of the artificial nitrogenous fertilisers used by farmers in the United 

 Kingdom. 



