View report page

109
the difficulty in the definition of black smoke by saying that it was so
dense as to effectually obscure the top of the chimney. That evidence
in many cases enabled the magistrate to convict. I think, however,
that had the defendant been supported by better technical evidence the
magistrate would not have been able to arrive at the opinion that the
case in regard to "black smoke" was sufficiently proved.
The blackness or darkness of smoke largely depends on the position
from which you view it. On a dull day viewed from the top of a
building considerably above ground level and against a darkened background
the smoke would appear many degrees darker than when viewed
on a fine sunny day, the observer being on the ground level with the sky
as a background.
Sanitary officers in giving evidence generally state that in addition
to the top of the shaft being obscured the blackness of the smoke was
of the colour of something decidedly black such as a black hat, which is
a familiar expression, but I question whether such blackness in reality
can ever exist.
Smoke proved to be in any way short of this definite blackness
must tell seriously against a conviction.
To obviate this dark colour of smoke the exhaust steam is sometimes
turned into the shaft, and this materially lightens the colour of
the smoke.
The quantity of black smoke emitted from a chimney is no measure
of the amount of smoke generally given off by chimney shafts. Some
firms who seriously charge the atmosphere around their works with
smoke give off from their chimney shafts only brown smoke. This,
however, is almost as much sun obscuring as black smoke. The absolutely
worst offender in the Borough is a shaft from a public concern which
consistently smokes all day with very small intervals, but, owing to the
exhaust steam, it is seldom that the volume of smoke is entirely black.
The difficulty in getting convictions, especially since the Chelsea
case, has been such as to make it necessary to have strong confirmatory
evidence before the prosecutions are entered upon. This entails
constant observations, and the expense of employing in smoke
observations a number of inspectors, together with the indisposition on
the part of many of the Councillors of the Local Authority to prosecute
ratepayers has made prosecutions almost impossible.