alternate currents of high potential and frequency. We may connect an
insulated line to a source of such currents, we may pass an
inappreciable current over the line, and on any point of the same we
are able to obtain a heavy current, capable of fusing a thick copper
wire. Or we may, by the help of some artifice, decompose a solution in
any electrolytic cell by connecting only one pole of the cell to the
line or source of energy. Or we may, by attaching to the line, or only
bringing into its vicinity, light up an incandescent lamp, an
exhausted tube, or a phosphorescent bulb.
However impracticable this plan of working may appear in many cases,
it certainly seems practicable, and even recommendable, in the
production of light. A perfected lamp would require but little energy,
and if wires were used at all we ought to be able to supply that
energy without a return wire.
It is now a fact that a body may be rendered incandescent or
phosphorescent by bringing it either in single contact or merely in
the vicinity of a source of electric impulses of the proper character,
and that in this manner a quantity of light sufficient to afford a
practical illuminant may be produced. It is, therefore, to say the
least, worth while to attempt to determine the best conditions and to
invent the best appliances for attaining this object.
Some experiences have already been gained in this direction, and I
will dwell on them briefly, in the hope that they might prove useful.
The heating of a conducting body inclosed in a bulb, and connected to
a source of rapidly alternating electric impulses, is dependent on so
many things of a different nature, that it would be difficult to give
a generally applicable rule under which the maximum heating occurs. As
regards the size of the vessel, I have lately found that at ordinary
or only slightly differing atmospheric pressures, when air is a good
insulator, and hence practically the same amount of energy by a
certain potential and frequency is given off from the body, whether
the bulb be small or large, the body is brought to a higher
temperature if inclosed in a small bulb, because of the better
confinement of heat in this case.
At lower pressures, when air becomes more or less conducting, or if
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