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38
Each of these methods has its advantages, but none is unaccompanied
by some drawback. A sample apparatus of each kind has been inspected
and carefully examined while in operation by the Special
Committee appointed for the purpose.
A few years ago numerous experiments were made by Dr. Ransome
(of Nottingham), and Dr. Seaton (of London), for the purpose of
ascertaining the singeing point of various textile fabrics. The result
of the experiments showed that almost all materials may be kept at
a dry heat of 250° for two or three hours without risk of damage.
Dr. Seaton showed, at a meeting of the Society of Medical Officers of
Health, an hospital blanket which had been baked at this temperature
thirty times, and which was in perfectly good condition. At a dry
heat a little above this (255° or 260°) most fine fabrics begin to scorch,
and if they are exposed for any length of time, they rapidly begin
to change colour. If, however, super-heated steam be used instead
of heated air, this temperature may be exceeded by ten degrees
without damage. Two hundred and fifty, then, is probably the limit
to which dry heat should be allowed to rise in the oven; but the
infected articles should certainly be exposed to at least this temperature,
which is just sufficient to destroy the poison of Small Pox
or Fever. It will thus be seen that a very few degrees of heat make
all the difference between scorching on the one hand, and inefficiency
on the other. Now this delicate regulation is, with an ordinary
furnace almost impossible, but it can easily be managed by means of
gas; and the self-acting disinfecting stove of Dr. Eansome answers
its purpose most admirably, as by an automatic arrangement the gas
is turned off when the mercury registers a certain temperature; in
fact, the mercury itself does the regulating; for, as it rises in a glass
tube exposed to the heat of the oven, it gradually encroaches upon an
opening through which the gas passes to the burners, and shuts off
the supply. Inside the oven is another ingenious arrangement for the
prevention of fire. It has occasionally happened that lucifer matches
have been allowed to remain in the pockets of clothing submitted to
disinfection, and that these have become ignited at the necessary
temperature of 250°. Should this at any time happen, the temperature
would thus immediately rise many degrees above 250°; and to provide
against this accident, dampers, suspended by chains, are placed over
both inlet and outlet, and one link of each chain is composed of fusible
metal, an alloy of lead and bismuth, which melts at a temperature of