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34
A new daily smoke and sulphur dioxide measuring station,
complementary to the above, was installed on the roof of the
Public Health Department at Lancaster Grove in November, 1954.
Since 1st December, 1954, the mean concentration of sulphur
dioxide and smoke has been ascertained daily by Mr. E. Ulrich,
one of your Sanitary Inspectors.
Our highest reading to date was obtained after thick
fog on 20th January, 1955, when the filter paper was discoloured
thus:
The smoke instrument consists of an electrically
operated air pump which continually aspirates a measured quantity
of air through a filter paper, thus producing, with smoky air, a
dark stain. At the same time, the induced air is passed through