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comment draft definitions and methods of testing, which should help to clear up
the rather vague application of terms concerning matters which may at times
endanger human lives, and are of very great importance in connection with all fire
risks from the point of view either of safety or insurance.
Atmospheric
Pollution
Committee.
The Council through its laboratory services makes a considerable contribution
to the work of the Committee on Atmospheric Pollution of the Department of
Scientific and Industrial Research. During the past years a process for determination
of sulphur acids in air has been the subject of experiment and the details are now
available. Results obtained at County Hall by this process show that London air
may contain from 0.05 per million volumes of sulphur dioxide on a clear day, up
to 0.52 in fog, and the data obtained were found valuable in connection with the
presentation of the Council's case at the Fulham Power station inquiry.
Visibility.
Visibility.—Observations of visibility in all directions at midday from the
fleche at County Hall were continued during 1930. As the results of 7 preceding
years were available a reasonable comparison of the year's results with the average
of preceding years was made. The average of the greatest distance at which known
objects could be distinguished was calculated for each calendar month of the six
years for quadrants embracing 45° on either side of each of the four cardinal points.
The results show that visibility is greatest, on the average, at all times of the
year in a southerly direction and markedly so from May to September, that visibility
over the two quadrants centred on north and east respectively is low and very
similar for the two quadrants, whilst the western quadrant occupies an intermediate
position. The maximum distance of visibility in July or August is from six to eight
times that during the months of lowest visibility, November to February. Compared
with the averages of the preceding years, 1930 must be considered a year of good
visibility, omitting the four months when the range of visibility is about one mile
only, the northern visibility was below the average in March only, the southern in
May and September only and the western in September only. The greatest excesses
of 1930 over the seven preceding years were in the semicircle north-west to southeast,
the increased southerly and westerly distances being less marked.