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49
suspension, then with some show of reason it may
be argued that the condition of the Sewer was contributory
to the result.
If, on the other hand, it can be demonstrated that
sulphuretted hydrogen in large volume is not a
normal constituent, but as a matter of fact was
found on this occasion only, then the fouling of the
atmosphere of the Sewer at the time of the accident,
and the fouling of the residual sewage, should be
regarded as the work of one and the same agency.
SUBSEQUENT TESTS OF RESIDUAL SEWAGE.
In order to put the question to the test of experiment,
sufficient time was allowed to pass after the accident to
permit the fouling, which manifestly accompanied that
event, to clear away, and the Sewer to resume its normal
condition. After the lapse of 12 days, on May 16th, the
depression from which the first sample was taken was again
requisitioned. On this occasion it was found that the
sulphuretted hydrogen which before was so large a constituent
had almost entirely disappeared. Analysis proved
that this gas was now represented only by a percentage of
1.21.† To provide against any accidental inaccuracy a
third sample was taken on May 19th. The result of
analysis proved to be even more significant than on the
previous occasion. Sulphuretted hydrogen in the interval
had entirely disappeared. The sample did not show a
trace.‡ The Sewer was kept under observation for many
days, and as the characteristic odour of sulphuretted
hydrogen was not again noticed, further investigation by
analysis was deemed unnecessary.
† Vide Appendix No. 2.
‡ Vide Appendix No. 3.
E *