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The Railway Receiver has collected
some curious examples of the way in which fires may be set. In
one instance, where some waste, which had been used with mineral
oil, had been thrown into a safe place, an insect crawled through
it, and then, carrying some pieces of the oily fiber sticking to
his body, made his way to a gas jet. The cotton fibers which
adhered to him caught fire, and he dropped, blazing, to the floor,
setting the building on fire. In another case, a quantity of
waste was said to have been ignited by the friction of a belt
running close to it. This, however, may be considered doubtful.
The friction of a belt against soft cotton is by no means of a
nature to produce great heat, and a much more rational explanation
is to be found in the supposition that an electric spark passed
from the belt to some conducting substance through the cotton,
which it ignited on its way, as sparks of frictional electricity
can easily do. In fact, the electrical effects accompanying
the running of large belts are quite important, and it is probable
that more than one fire has been due to them. Sparks can be taken
by the finger from almost any large belt in motion, and we have
known a case where an ingenious engineer, by fixing a metal comb
near the belt, succeeded in drawing off enough high tension
electricity to enable him to light the gas jets in and about the
engine room without matches by simply touching them, after turning
on the gas, with a wire connected to the comb.
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In two cases destructive fires have been
caused by water. In one of these a flood caused the water to
rise high enough in a factory to reach a pile of iron filings.
The filings, on contact with the water, oxidized so rapidly that
they became intensely heated, and then set fire to the neighboring
wood-work and the building was destroyed. The the other case, the
water from the engines, during a fire, found its way into a shed
containing quicklime, and the heat generated by the slaking of
the lime set fire to the shed, and this to other buildings.
Quicklime fires, however, are not uncommon. Many vessels carrying
quicklime have probably been burned by the admission of water to
the lime through a trifling leak, and no architect or builder needs
to be told how intense the heat of slaking lime can be. Glass
globes, which act as lenses, often set fires, and it has recently
been claimed, on high authority, that the convex glass used in
sidewalk lights are dangerous, and should be abandoned in
favor of lights with flat tops. As the convex glasses receive
and transmit much more light than the flat ones, particularly in
muddy weather, it seems hard to be obliged to give them up, and
perhaps a lens might be made convex on the outside and concave
on the inside, the concavity being equal to or greater than the
convexity, so that rays of sunlight would either pass through
unchanged in direction or would be dispersed instead of being
concentrated, so as to unite the advantages of the convex form
with complete security.
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