418 Composition and Practical Value of Native Guano. 
possibly act beneficially upon sewage in virtue of its antiseptic 
properties. 
It is, however, not my purpose in the present communication 
to make any further remarks on the merits or demerits of the 
chemical agents recommended by the patentees of the ABC 
process, nor do 1 intend to discuss at length how far this process 
fulfils the high expectations of its originators, and meets the 
sanitary difficulties which have to be overcome in the disposal of 
town sewage. Ample information, referring specially to the 
sanitary aspect of the great sewage question, will be found 
in the able reports for 1870 of the Rivers Pollution Commission; 
(1868). Suffice it to state here that the Commission, on the 
strength of numerous experiments, have come to the conclusiori 
that the ABC process fails in purifying sewage to such an 
extent as to render it admissible into running water. 
As far as my own experience entitles me to express an opinion 
of the efficacy of the ABC process for purifying sewage, I 
would observe that I agree in the main with, but do not fully con- 
cur in, the view of the Rivers Pollution Commissioners. Sewage 
clarified by the ABC process, or by the plan recommended by 
Mr. Leek, or Dr. Anderson of Coventry (who both rely mainly 
on the efficacy of sulphate of alumina as a precipitating and 
disinfectant agent), or purified by any other equally efficacious 
process, I am of opinion cannot be rendered sufficiently pure to- 
be admissible into running water when the sewage of a large 
town and populous district has to be disposed of, and the 
available running water, comparatively speaking, is too incon- 
siderable in proportion to the sewage which is poured into it, 
clear though it may be. But if the sewage of a small town has 
to be disposed of, and suitable land for irrigation cannot be pro- 
cured, or only at an immoderate sacrifice of money ; and, on the 
other hand, a good sized river or abundance of running water 
is near, into which the effluent and clarified sewage may be run, 
I believe the discharge of such sewage under these circumstances 
would not create a nuisance. 
It is quite true that sewage, however well purified it may be by 
any known process of precipitation, always contains a good dea,l 
of saline mineral matter and obnoxious organic matter in solu- 
tion, and for these reasons ought not to be poured in large 
quantities into a shallow watercourse ; but if the disinfected and 
clear sewage of a small town be poured into a large bulk of 
running Avater, it will not materially augment the saline and 
earthy matters naturally present in the water, and the small 
amount of organic impurities, when brought into contact with 
the dissolved air of a large bulk of running water, will rapidly 
become oxydised, and rendered perfectly inodorous and harmless. 
