(_From the Treatise on Electricity--in the Library of Useful
Knowledge_.)
The colours produced by the electric explosion of metals have been
applied to impress letters or ornamental devices on silk and on paper.
For this purpose Mr. Singer directs that the outline of the required
figure should be first traced on thick drawing paper, and afterwards
cut out in the manner of stencil plates. The drawing paper is then
placed on the silk or paper intended to be marked; a leaf of gold is
laid upon it, and a card over that; the whole is then placed in a
press or under a weight, and a charge from a battery sent through the
gold leaf. The stain is confined by the interposition of the drawing
paper to the limit of the design, and in this way a profile, a flower,
or any other outline figure may be very neatly impressed.
Most combustible bodies are capable of being inflamed by electricity,
but more especially if it be made to strike against them in the form
of a spark or shock obtained by an interrupted circuit, as by the
interposition of a stratum of air. In this way may alcohol, ether,
camphor, powdered resin, phosphorus, or gunpowder be set fire to. The
inflammation of oil of turpentine will be promoted by strewing upon it
fine particles of brass filings. If the spirit of wine be not highly
rectified, it will generally be necessary previously to warm it, and
the same precaution must be taken with other fluids, as oil and
pitch; but it is not required with ether, which usually inflames
very readily. But on the other hand, it is to be remarked that the
temperature of the body which communicates the spark appears to have
no sensible influence on the heat produced by it. Thus the sparks
taken from a piece of ice are as capable of inflaming bodies as those
from a piece of red-hot iron. Nor is the heating power of electricity
in the smallest degree diminished by its being conducted through any
number of freezing mixtures which are rapidly absorbing heat from
surrounding bodies.
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