ox THE TKEATHENT AND TTILIZATIOX Or fsEWAGE. 151 



sioners cousidercd the subsoil-water to contain as much chloriue as the 

 •water of the river TafF, whereas actual analysis of it shows it to contain only 

 0-92 against 1*2 of chlorine in the river-water. Had we taken the composi- 

 tion of the river-water as given by the Commissioners, the dilution would 

 have appeared in this case to be 1-7 gallon of subsoil-Avater to 1 of sewage, 

 instead of 1-39 to 1. 



Now the total nitrogen in solution in 100,000 parts of sewage was 1*40, 

 in the effluent water 0-G5, and in the subsoil-water 0-05 (see Table). 

 Again, one volume of this sewage, mixed with 1-39 volume of this subsoil- 

 water, would give 2-39 volumes of water, containing exactly 0-07 part of 

 nitrogen in solution in the 100,000 parts — that is to say, that the apparent 

 diminution of the nitrogen in solution is, within a small fraction, entirely due 

 to dilution with subsoil-water ; and the nitrogen retained in the soil is eipial 

 to the amount in the suspended matters of the sewage, that is to say, rather 

 more than a quarter of the total nitrogen. 



What is most important, however, is that, although all the nitrogen 

 originally in solution is lost, it is almost all oxidized; for about \\ of the 

 nitrogen in the effluent water is in the form of innocuous nitrates and 

 nitrites. 



In the summer the dilution with subsoil-water was, according to the 

 gaugings, equal to about twice the volume of the sewage. As the chlorine 

 in the subsoil-water was not determined in the summer, we can only say that 

 the smaller proportion of total nitrogen in solution in the effluent water 

 seems to confirm the results of the gaugings. 



The effluent water this summer was not quite so pure as last winter, but 

 still four fifths of its nitrogen was in the form of nitrates and nitrites. 



It is to be noted that the sewage was cooled by its percolation through the 

 soil, and especially so in summer. 



The general results seem to be that by the process the suspended matters 

 are removed, and the ammonia and nitrogenous organic matters in solution 

 are almost completely oxidized, and escape in the effxuent water as nitrates 

 and nitrites ; so that the sewage is satisfactorily purified, though the process 

 cannot be looked upon as one of utilization. 



Section VII. — Breton's Farm, near Bomforcl. 



It will be in the remembrance of the members of the British Association 

 that the Committee has been conducting a series of observations on the appli- 

 cation of the sewage of the town of Romford to this farm, both as to the 

 purification of the sewage and its utilization as a manure ; accordingly the 

 observations and analyses recorded in previous years have been continued 

 during the past year, and the results will be found in the accompanying 

 Tables. 



The Committee have, however, extended their observations still further 

 during the past year, and have supplemented them by the particulars of the 

 crops which have been grown on the farm during the twelve months from 

 March 25th, 1871, to ]\Iareh 24th, 1872, both days inclusive. But to make 

 this inquiry more complete, and of greater practical utility, the Committee 

 made an alteration in the form of the analysis of the sewage and effluent 

 •water, so as to determine the total nitrogen. 



The observations Avhich were made in rolalion to the crops gave the fol- 

 lowing results ; — ■ 



