the fantastic inventions of nikola tesla - Exopolitics Hong Kong

A different arrangement used in some of the bulbs constructed is illustrated in Fig. 23. In this instance a non-conductor
m is mounted in a piece of common arc light carbon so as to project some small distance above the latter.
The carbon piece is connected to the leading-in wire passing through a glass stem, which is wrapped with several
layers of mica. An aluminium tube a is employed as usual for screening. It is so arranged that it reaches very nearly
as high as the carbon and only the non-conductor m projects a little above it. The bombardment goes at first against
the upper surface of carbon, the lower parts being protected by the aluminium tube. As soon, however, as the nonconductor
m is heated it is rendered good conducting, and then it becomes the centre of the bombardment, being
most exposed to the same.
I have also constructed during these experiments many such single-wire bulbs with or without internal electrode, in
which the radiant matter was projected against, or focused upon, the body to be rendered incandescent. Fig. 24
illustrates one of the bulbs used. It consists of a spherical globe L, provided with a long neck n, on the top, for increasing
the action in some cases by the application of an external conducting coating. The globe L is blown out on
the bottom into a very small bulb b, which serves to hold it firmly in a socket S of insulating material into which it
is cemented. A fine lamp filament /, supported on a wire w, passes through the centre of the globe L. The filament
is rendered incandescent in the middle portion, where the bombardment proceeding from the lower inside surface
of the globe is most intense. The lower portion of the globe, as far as the socket S reaches, is rendered conducting,
either by a tinfoil coating or otherwise, and the external electrode is connected to a terminal of the coil.
The arrangement diagrammatically indicated in Fig. 24 was found to be an inferior one when it was desired to render
incandescent a filament or button supported in the centre of the globe, but it was convenient when the object
was to excite phosphorescence.
In many experiments in which bodies of a different kind were mounted in the bulb as, for instance, indicated in Fig.
23, some observations of interest were made.
It was found, among other things, that in such cases, no matter where the bombardment began, just as soon as a
high temperature was reached there was generally one of the bodies which seemed to take most of the
bombardment upon itself, the other, or others, being thereby relieved. This quality appeared to depend principally
on the point of fusion, and on the facility with which the body was •' evaporated," or, generally speaking,
disintegrated—meaning by the latter term not only the throwing off of atoms, but likewise of larger lumps. The
observation made was in accordance with generally accepted notions. In a highly exhausted bulb electricity is
carried off from the electrode by independent carriers, which are partly the atoms, or molecules, of the residual
atmosphere, and partly the atoms, molecules, or lumps thrown off from the electrode. If the electrode is composed
of bodies of different character, and if one of these is more easily disintegrated than the others, most of the
electricity supplied is carried off from that body, which is then brought to a higher temperature than the others, and
this the more, as upon an increase of the temperature the body is still more easily disintegrated.
It seems to me quite probable that a similar process takes place in the bulb even with a homogeneous electrode, and
I think it to be the principal cause of the disintegration. There is bound to be some irregularity, even if the surface is
highly polished, which, of course, is impossible with most of the refractory bodies employed as electrodes. Assume
that a point of the electrode gets hotter, instantly most of the discharge passes through that point, and a minute
patch is probably fused and evaporated. It is now possible that in consequence of the violent disintegration the spot
attacked sinks in temperature, or that a counter force is created, as in an arc; at any rate, the local tearing off meets
with the limitations incident to the experiment, whereupon the same process occurs on another place. To the eye the
electrode appears uniformly brilliant, but there axe upon it points constantly shifting and wandering around, of a
temperature far above the mean, and this materially hastens the process of deterioration. That some such thing
occurs, at least when the electrode is at a lower temperature, sufficient experimental evidence can be obtained in
the following manner : Exhaust a bulb to a very high degree, so that with a fairly high potential the discharge
cannot pass—that is, not a luminous one, for a weak invisible discharge occurs always, in all probability. Now raise
slowly and carefully the potential, leaving the primary current on no more than for an instant. At a certain point,
two, three, or half a dozen phosphorescent spots will appear on the globe. These places of the glass are evidently
more violently bombarded than others, this being due to the unevenly distributed electric density, necessitated, of
course, by sharp projections, or, generally speaking, irregularities of the electrode. But the luminous patches are
constantly changing in position, which is especially well observable if one manages to produce very few, and this
indicates that the configuration of the electrode is rapidly changing.
From experiences of this kind I am led to infer that, in order to be most durable, the refractory button in the bulb
should be in the form of a sphere with a highly polished surface. Such a small sphere could be manufactured from a
diamond or some other crystal, but a better way would be to fuse, by the employment of extreme degrees of