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visited. The night was fine and cold. Only two persons, both females, were found sheltering under
arches or on staircases—the lowest number yet recorded. In the streets, the number of homeless persons
also showed a considerable reduction. On the night in question 1 man and 6 women were found, as
compared with 19 men and 5 women in 1917, and 296 men and 76 women in the early part of 1914.
The common lodging house population was less numerous than on any previous occasion, there
being 12,522 inmates as compared with 13,679 in 1917, and 20,173 in the early part of 1914. In the
free shelters and labour homes not licensed as common lodging houses there was also a reduction in
the number of inmates, 32 men and 74 women being accommodated, as compared with 64 men, 159
women and 7 children in 1917. The number of persons in London casual wards on the night in question
was 82 as compared with 89 at the time of the last census, and in Rowton Houses 4,108 as against 3,950.
Work of the Chemical Branch.
The work of the chemical branch of the department is carried out at the central laboratory at
Savoy Hill and at the laboratories at the two sewage outfalls at Barking and Crossness. During the year
under consideration a laboratory has been partly equipped at the Greenwich generating station in order
that systematic work and technical investigations required by the Highways Committee may be
undertaken.
Central laboratory.—The work at the central laboratory normally includes the examination of
samples received under such statutes as the Fertilisers and Feeding Stuffs Act, 1906, the Petroleum
Acts, the London Building Act and certain of the Council's General Powers Acts. In connection with
the administration of the Petroleum Acts, 69 analyses were made of gases used for creating a definitely
non-explosive atmosphere in certain dry cleaning and de-greasing plants in which petroleum spirit
is used.
Monthly samples of rainwater collected in special gauges at six open spaces in the county were
examined in connection with the work of the Atmospheric Pollution Committee, in which the Council
is co-operating with other bodies all over the country.
The results of the examination of upwards of 800 samples of milk are dealt with in the school
section of this report. Two samples of dried milk, both guaranteed full cream, were examined. One
was found to be genuine dried whole milk. The other was dried separated milk. Owing no doubt to
the food shortage and the difficulty of enforcing requirements as to quality, only very few samples of
foods supplied to the Council's residential institutions were received for examination. Previous experience
as well as that obtained with milk in the year under consideration shows, however, that the knowledge
that deliveries will be submitted to examination has a wholesome effect on the quality of the supply,
apart from the actual detection of inferior materials.
The chemical examination and determination of the heating value of coal supplied to the Council's
generating station at Greenwich has for many years been carried out by the chemical stafE. The results
obtained in 1918 have shown that a great deal of very low grade coal is now on the market. Samples
yielding as much as 19 per cent, of ash were received on many occasions, the greatest amount found
in the year being 28 per cent. Recently this figure has been exceeded. The use of coke at the generating
station owing to the shortage of coal has been attended with considerable success. This material varies
much less in its general properties than the coals from which it is made. The examination of 90 samples
has, however, shown that coal of very high ash content is now used in gas making, leading to the formation
of a less valuable and more difficultly combustible coke. The examination of such more or less abnormal
samples of coal and coke has presented some experimental difficulties which have been successfully
overcome by the various new devices adopted by the chemical staff. In all 752 samples of solid fuel
were examined, 662 samples of coal and 90 samples of coke.
An investigation for the Public Control department of the inflammable properties of aeroplane
" dope " (celluloid varnish) involved a considerable amount of experimental work.
An investigation into the cause and prevention of corrosion of lead sheathing for electric conductors
is being carried out in collaboration with the electrical branch of the tramways department. The results,
so far obtained, seem to indicate fairly clearly the most important cause of such corrosion, but the
matter is not yet fully investigated.
The Outfalls.—The work at the laboratories at the two outfalls includes the routine daily examination
of sewage effluent and sludge and of river water collected at high and low water at both outfalls.
A long series of records, dating back to the beginning of the present system of sedimentation, is thereby
continued and data are available, not only for daily information as to the quality of the materials in
question, but for larger problems which may at any time arise. In 1918, 730 samples of sewage, 730
samples of effluent and 2,154 samples of sludge were examined at the two outfalls, as well as 395 samples
of lower river and estuary waters.
Examination of the tideway.—Allusion was made in last year's report to the systematic examination
of the tideway of the River Thames, which was undertaken as a means of observation of the effect of
varying treatment of sewage at the Council's outfalls, and with a view to solving certain problems
connected therewith. The results so far obtained have been recently summarised and tentatively discussed
in a report to the Main Drainage Committee of the Council. They are very briefly presented below :—
I. Results obtained—
The various chemical tests, more particularly the percentage saturation with dissolved
oxygen, show that there is very little deterioration of the water coming down from the nontidal
portion of the river until, say, Isleworth is reached, and no marked deterioration above
Putney. From this point down to Greenhithe, the average saturation with dissolved oxygen