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Generally, it may be said that the deposit at the Welfare Centre indicates a much greater degree
of atmospheric pollution there than at the Town Hall. The figures, however, show a few remarkable
inconsistencies, notably in August when the readings for the Welfare Centre and the Town Hall were
14.39 and 14.40 tons per square mile, respectively; and in April and January when the figures in
respect of the Welfare Centre were only slightly higher than those for the Town Hall. On the other
hand, during May, June and March there was approximately double the amount of deposit at the
Welfare Centre as compared with the control. At the time it was not known whether these differences
were in any way associated with output at the generating stations.
It is important that readings of this kind should be considered in conjunction with similar readings
taken in other parts of London and of the country, as in many respects atmospheric pollution is
relative and what might be regarded as a serious case in a rural district might appear to be very
moderate as compared with the degree of pollution prevalent in an industrial town.
The readings shown in the table were submitted to the Superintendent of Observations,
Atmospheric Pollution Research, Department of Scientific and Industrial Research, who kindly gave
his views upon the results of the year's observations in the following report:—
"The results obtained in this investigation are quite positive in that they show clearly that the
rate of deposition of solids in the Lisson Grove area is consistently much higher than that at the Town
Hall. The largest differences lie in the insoluble matter and particularly in the ash content of the
insoluble matter—a result which suggests that the greater rate of deposition at Lisson Grove has been
most likely due to emission from industrial installations in the near vicinity. Thus it is seen that the
average value for insoluble matter at Lisson Grove is almost twice that for the Town Hall.
"The largest individual consumers of fuel in the Lisson Grove area are the electricity generating
stations at Lodge Road and Aberdeen Place and there are, in addition, railway marshalling yards
between Lisson Grove and Park Road. These possible sources of atmospheric pollution lie respectively
to the north-east, west and south-east of the observing station at Welfare Centre No. 2 and, therefore,
the deposit gauge at this station will not be collecting the pollution from all three sources at any one
time. The prevailing wind over the area is south-west and thus it is probable that of the three possible
sources, the gauge will be exposed most frequently to the pollution from the generating station at
Aberdeen Place. This does not, however, necessarily mean that the quantity of material collected
by the gauge will have arisen mainly from this generating station, since nothing is known about the
relative rates of emission of pollution by the three sources. Further information on this matter
might be obtained by siting another gauge downwind, i.e., to the north-east of the Lodge Road
generating station.
"Although the deposited matter at Lisson Grove is higher than that at the Town Hall, it cannot,
in comparison with other similarly situated areas, be regarded as abnormally high. This is illustrated
by the accompanying Table (No. 7) which shows the average monthly rates of deposit over the same