i88i.j The Sanitary Institute of Great Britain. 477 
thousand utterly disinterested witnesses — medical men, 
chemists, engineers, municipal authorities, &c. — who have 
visited and carefully inspected places where the process in 
question was being worked, and would declare the above 
charge utterly unfounded. It has, indeed, been formally 
denied in the official report drawn up by Mr. Keats, chemist 
to the Metropolitan Board of Works, by the Sewage Com- 
mittee of the Leeds Corporation, &c. ; yet the slander — we 
can use no milder term — is still circulated as an argument 
against every chemical method of treating sewage, and its 
authors have never had the honesty to come and examine 
whether an observation, perhaps made under some peculiarly 
unfavourable circumstances, in the very infancy of sewage 
precipitation, holds good at the present day. Again, it was 
said that the effluent after treatment contained more ammo- 
niacal salts than the original sewage. This was at the time 
perfectly true, and the Commissioners well knew wherefore, 
— that is, because ammonia alum was injudiciously used as 
a precipitating agent. Mentioning the faCt they ought, in 
common candour, to have mentioned the cause, and to have 
admitted that such cause has been removed, and that the 
charge falls to the ground. So far from this, a former attache 
to the Commission has repeated the statement within the 
last few years, though if at all acquainted with the history 
of the sewage-question he must know that in the process in 
question ammonia alum has long ago been laid aside in favour 
of cake alum (aluminium trisulphate). 
Turning to another quarter: a precipitating process was 
worked experimentally in 1872, under close inspection. The 
chemical report as to the purification of the water and the 
freedom from nuisance was most favourable. The expense 
of working the process was made out to be ruinously heavy ; 
but by what means ? Coal was in the year 1872 at a fancy 
price, and the process was debited not with the ordinary cost 
of fuel, but with this special figure. Sulphate of alumina 
commanded then double its present price. More than that, 
in their anxiety to make the cost of the operations appear 
prohibitive, the authorities in charge insisted on debiting the 
process with the salary of a chemist who went down daily 
during the three months’ trial to draw a check-sample of 
effluent water on behalf of the patentees ! Yet in spite of 
the introduction of these and other palpably anomalous 
items, the document in question is still paraded by irriga- 
tionists as a proof of the prohibitive cost of chemical 
methods of sewage-purification. 
But we must approach our more immediate question. 
