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(2.) That a naked light was brought into contact with an explosive
mixture of gas.
The second accident occurred about six o'clock on the morning of the
29th September last, and was of an extremely serious nature.
The facts are accurately described in the letter from the County
Council dated 20th October. 1891.
The ignition of the explosive mixture in the street box was, it
appears, undoubtedly caused by a breakdown in a pilot wire, i.e., an
insulated wire connecting a distant point on the system of distribution
with the central station by means of which the exact pressure at the
distant point is indicated at the station.
I attach a piece cut from this pilot wire where the fault occurred.
The wire is insulated and then coated with lead. There appears to
have been a defect in the insulation at this point very possibly caused by
a sharp kink, and an electric arc was formed, shown by the fusion of the
end of the conductor.
The causes of this accident are:—
(1.) That the Company had not efficiently protected this street box
against an accumulation of gas as required by regulation, and
that in consequence of this neglect on their part an accumulation
of gas did occur in it.
(2.) That a failure of insulation occurred in the pilot wire, giving rise
to an electric arc in contact with an explosive mixture of gas.
PRECAUTIONS TO BE TAKEN.
It will be observed that in the case of each accident it is evident
that a principal cause was the failure on the part of the Company to
comply with the regulations imposed upon them by the Board of Trade,
and the most obvious precaution to be taken is a more strict compliance
with these regulations.
The exact dangers, the existence of which has now been forcibly
demonstrated, were clearly foreseen in framing the regulations, which
were purposely left in a general form in order that the judgment of the
Company's engineers might not be fettered in suiting their precautionary
measures to the exigencies of each particular case.
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