Sewage Precipitation. [August, 
dry manure contains nitrogen equal to 3*8 per cent of 
ammonia (consequently equal to ig per cent sulphate ot 
ammonia), and phosphoric acid equal to 5 per cent ot tri- 
calcic phosphate. These figures will be better undei stood 
if we remember that farmyard manure, in its normal condi- 
tion, contains only 0'40 per cent of nitrogen, or when abso- 
lutely dry i‘95 per cent (= 2'36 ammonia or ir8o sulphate 
of ammonia) and o‘i8 phosphoric acid (= 0^37 per cent tri- 
calcic phosphate). Surely a manure containing nearly twice 
as much ammonia as farmyard manure, and more than ten 
times as much phosphoric acid, is not to be despised ! 
Lastly comes the fourth conclusion of the Commissioners, 
that “ the manipulations required for the extraction and 
drying of this manure are attended with a nauseous odoui, 
especially in warm weather, and would occasion a serious 
nuisance if the Works were situate in or near a town.” 
On the contrary, Prof. Dewar and Dr. Tidy say— “ The 
sewage is completely and immediately deodorised, no escape 
of offensive odours from the sewage into the sui rounding aii 
taking place. The entire Works are, in our experience, free 
from any objectionable smell whatsoever. 
The investigation conducted by Prof. Dewar and Dr. Tidy 
is both more precise than that carried on by the late T. W. 
Keates, F.C.S., at Crossness, in 1872, and the results more 
satisfactory . Mr. Keates pronounced the effluent water as 
“ on the whole very good.” He declared himself to be. of 
opinion that such water was in a fit state to be admitted 
into any ordinary river without producing a dangerous degree 
of pollution.” But with commendable caution he pointed 
out the extremely dilute state of the sewage during the ex- 
periment, and remarked that it was <£ of couise impossible 
to say, at least from this experiment, how far the A BC 
treatment would defecate sewage of a stronger character.” 
In this respeCt Prof. Dewar and Dr. Tidy have been more 
fortunate. They have encountered sewage much stronger 
and ranker than any which Mr. Keates ever witnessed at 
Crossness, and they have found and declaied that the ABC 
process is competent to defecate such liquids. 
The question now only remains, How often and how autho- 
ritatively the truth must be reiterated before it will be ac- 
cepted, and before the misstatements of the. Royal Rivers’ 
Pollution Commission fall into the discredit due to their 
character ? 
