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dump on neighbouring land of the hard-core of demolished street air raid shelters. Having regard
to Table 2, which compares the results obtained in Golden Lane with stations in other areas, the main
reason for the upward general trend of deposit is probably the prolonged inclement weather experienced
in most parts of the country during the year.
In Table 3 the results indicate a general decrease in the concentration of suspended impurity in
the air. Since the main source of this soot and tar pollution is the domestic fire, burning raw coal,
the shortage of adequate supplies of this fuel may account for the reduction in the concentration.
Table 4 is a comparison with other stations of the mean monthly concentration of sulphur
dioxide observed by the volumetric method. There is an increase of 0.0l parts per million of sulphur
dioxide in the City. In two of the other three stations for which results are given, the figures are the
same as for 1949. The third shows a decrease. The concentration of sulphur dioxide varies considerably
from day to day and from hour to hour. In the month of November, 1950, when all kinds
of weather were experienced, varying from dense fog to gales with heavy rain, the daily mean concentration
was 0.154 parts per million. The highest daily figure recorded during the month was 0.326
and the lowest 0.052.
Table 5 records the results of observations by the lead peroxide method for determining the
concentration of sulphur dioxide. This method is designed to give a measure of the activity of attack
of the sulphur upon buildings, building stones and materials. The results are not strictly comparable
with the volumetric method as other factors besides the concentration have an effect in influencing
the activity of attack, e.g., in winter the surface of lead peroxide is usually moister, and consequently
more reactive, than in summer, and for the same reason the exterior surface of buildings are also
more liable in winter than in summer to attack by sulphur dioxide. The results in Table 5 indicate a
reduction of the concentration in the City and the other places chosen for comparison.
DEPOSITED MATTER.
Table 1. Mean Monthly Rates of Deposit at Golden Lane.
Tons per square mile.
1949
1950
Total Solids
18.72
27.15
Total undissolved matter
8.74
10.19
Tarry matter
0.68
0.52
Other combustible matter
1.90
2.75
Ash
6.16
6.85
Total dissolved matter
9.99
16.96
Calcium
1.56
3.35
Chloride
1.92
2.17
Sulphate
3.13
3.63
Table 2. Comparison of Total Solids deposited during 1938/39, 1949 and 1950 at Golden Lane
Godalming, Walsall and Westminster.
Tons per sq. mile per month.
Year ended
31 3 1939
31/12 1949
31 12/1950
London—
Golden Lane
21.83
18.72
27.15
Westminster
22.30
21.32
37.59
Godalming
4.61
5.97
6.37
Walsall
19.28
15.25
22.34
SUSPENDED IMPURITY.
Table 3. Comparison of the Mean Monthly Concentration of Suspended Impurity by the Volumetric
Method.
M illiqrams per 100 cubic metres.
1949
1950
Golden Lane
10.15
9.98
Birmingham
30.30
23.10
County Hall, London
31.50
25.53
Rye
0.018
1.40
Salford
64.83
53.75
SULPHUR DIOXIDE.
Table 4. Comparison of the Mean Monthly Concentration of Sulphur Dioxide by the Volumetric
Method.
Parts per million of Sulphur Dioxide.
1949
1950
Golden Lane
0.09
0.10
Westminster
0.09
0.09
Bilston
0.10
0.07
Crossness
0.03
0.03
Table 5. Comparison of the Mean Monthly Concentration of Sulphur Dioxide by the Lead Peroxide
Method.
Milligrams of S03 per 100 cm2
1949
1950
City of London.
Golden Lane
2.74
2.66
Finsbury Circus Gardens
2.53
2.32
Godalming
0.42
0.27
Walsall
2.83
2.74
Westminster
2.95
2.75