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necessity for costly land filtration of the effluent, recommended
hy the Royal Commission on Metropolitan Sewage Discharge,
with a view to ensure the removal of all odour and the possibility
of " secondary fermentation." The Board, in giving effect to
the views of their scientific advisers, have incurred and are still
incurring a large expenditure for works of construction, and in
the carrying out of the system adopted. Deferring, however, to
the objections made to the system, the Board last year retained
the services of Sir Henry Roscoe, as special adviser in this
matter, and they have recently consented to the request by
Sanitary Authorities—your Yestry among the number—to make
that gentleman's reports public. These reports, of which I
propose to submit a summary account, are five in number. The
first, dated 16th May, 1887, deals with " The Deodorization of
Sewage in the Metropolitan Sewers," the second, dated August
7th, 1887, with " The Deodorization of Sewage at the Outfalls."
(1.) With reference to the use of chemicals for the purpose
of disinfecting the emanations in the Board's Sewers, it appears
that a mixture of manganate of soda and sulphuric acid was
employed, at a cost, in 1886, of £40,000* for chemicals and labour,
with the result of reducing the number of complaints from 64
and 65 in 1883 and 1884, to 28 in 1886. Sir H. Roscoe
expresses the opinion that the manganate process does affect a
certain deodorization of the sewer emanations, but that the
quantity of manganate used in the sewers cannot affect the
nature of the sewage at the outfall, being quite insufficient to
oxidize even a small part of the putrescent fœcal matter, which
gives rise to the emanations. He cannot, moreover, bring him-
self to consider that the expenditure of over £40,000 a year is
commensurate with the results obtained, no medical evidence
having been brought forward to show that illness, much less that
any outbreak of an epidemic, has been traced to the emanations
complained of. He adds that if it be determined to disinfect
* The cost of chemicals used in 1886 is put in a subsequent report (vide
page 235) at " upwards of £80,000."