metal pipes filled with gas--the metal being the insulator, the gas
the conductor--supplying phosphorescent bulbs, or perhaps devices as
yet uninvented. It is certainly possible to take a hollow core of
copper, rarefy the gas in the same, and by passing impulses of
sufficiently high frequency through a circuit around it, bring the gas
inside to a high degree of incandescence; but as to the nature of the
forces there would be considerable uncertainty, for it would be
doubtful whether with such impulses the copper core would act as a
static screen. Such paradoxes and apparent impossibilities we
encounter at every step in this line of work, and therein lies, to a
great extent, the claim of the study.
I have here a short and wide tube which is exhausted to a high degree
and covered with a substantial coating of bronze, the coating allowing
barely the light to shine through. A metallic clasp, with a hook for
suspending the tube, is fastened around the middle portion of the
latter, the clasp being in contact with the bronze coating. I now want
to light the gas inside by suspending the tube on a wire connected to
the coil. Any one who would try the experiment for the first time, not
having any previous experience, would probably take care to be quite
alone when making the trial, for fear that he might become the joke of
his assistants. Still, the bulb lights in spite of the metal coating,
and the light can be distinctly perceived through the latter. A long
tube covered with aluminium bronze lights when held in one hand--the
other touching the terminal of the coil--quite powerfully. It might be
objected that the coatings are not sufficiently conducting; still,
even if they were highly resistant, they ought to screen the gas. They
certainly screen it perfectly in a condition of rest, but not by far
perfectly when the charge is surging in the coating. But the loss of
energy which occurs within the tube, notwithstanding the screen, is
occasioned principally by the presence of the gas. Were we to take a
large hollow metallic sphere and fill it with a perfect incompressible
fluid dielectric, there would be no loss inside of the sphere, and
consequently the inside might be considered as perfectly screened,
though the potential be very rapidly alternating. Even were the sphere
filled with oil, the loss would be incomparably smaller than when the
fluid is replaced by a gas, for in the latter case the force produces
displacements; that means impact and collisions in the inside.
No matter what the pressure of the gas may be, it becomes an important
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