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on health grounds; three of these became insane and are now in mental hospitals, one
is reported to have broken down with "nerves," one to have skin trouble and one to
have undefined ill health. It is noteworthy that in four of the six who failed on
grounds of health, blindness was due to optic atrophy. With the other classes of
blindness only two out of 70 failed on account of health. It is well known that optic
atrophy is usually a feature of cerebral disease and may be accompanied by more
general damage. Out of 15 cases in the group under review four were unfit for training
on medical grounds and eleven were fit for training.
The six cases noted as deaf, including one deaf and dumb, are all doing well in a
special class at Leatherhead. This result is very satisfactory. It might have been
thought that the combined defect would cause great difficulty, but when the
conditions are recognised and dealt with, the difficulty is found to be comparatively
slight.
Work of the Chemical Branch, 1927.
The work of this branch is carried out at tour laboratories, viz., the Central
Laboratory at County Hall, and the laboratories at the Northern and Southern
Outfalls and the Greenwich Power Station.
Central
laboratory.
Samples of various kmds examined during the year totalled 5,240, an increase
of nearly 11 per cent, on last year, and a considerable amount of work of an advisory
character was carried out. The samples were submitted by other departments of
the Council for examination as to their compliance with specific requirements or
their suitability for various purposes. The following table shows the number and
description of samples examined at the Central Laboratory:—
Building Materials 533
Coals (Ash tests, etc.) 18
Coke 20
Disinfectants 19
Drugs 35
Feeding Stuffs and Fertilisers 17
Foods, groceries, etc. 810
Gases 26
Meals (School) 13
Metals 13
Milks 1,519
Oils, Greases, etc. 209
Paints and Colours 331
Petroleum and Paraffin 188
Soaps, Shampoo Preparations, etc. 39
Rainwater 107
River waters 509
Ordinary water 27
Waters from softening plant 508
Water and deposit (bathing lakes) 168
Miscellaneous 105
Fire-resisting
materials and
appliances.
Considerable attention has been devoted to the testing of fire-resisting materials
such as woods and composite materials consisting of asbestos mixtures or similar
substances enclosed between sheets of wood or metal. Two general types of test
have been evolved: (a) beam breaking tests based on the time elapsing before a
beam of defined dimensions heated by a standard flame beneath it, breaks under
the downward stress of a given weight, and (b) thermal conducting tests, in which
a block of wood of defined thickness is heated on one side to 1,500 deg. F., and the
rate of rise of temperature of the far surface is determined. The electric furnace,
the thermo-electric thermometers and the beam breaking apparatus used in this
test have been made in the laboratory. This work is still going on, and other means
of testing fireproof materials are being tried.
In connection with the examination of fusible metal-soldered links for automatically
shutting ventilators on the outbreak of fire, the possibilities of making
more fusible metals than those in common use were investigated. It appears that
no alloy melting below 72.5 deg. C. can be made from ordinary metals without the
addition of mercury.
Building
materials.
Mortars and other building materials have been examined either as to compliance
with the by-laws or as to general fitness for use by tests to suit the special
requirements of each case.
Brittle fibres.
Among other matters of interest a rope which broke under the weight of one
man within a week of passing the tensile test used by the Fire Brigade was found