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 temperature,
some oxide--as, for instance, zirconia--into a small drop, and then
keep it in the bulb at a temperature somewhat below its point of
fusion.

Interesting and useful results can no doubt be reached in the
direction of extreme degrees of heat. How can such high temperatures
be arrived at? How are the highest degrees of heat reached in nature?
By the impact of stars, by high speeds and collisions. In a collision
any rate of heat generation may be attained. In a chemical process we
are limited. When oxygen and hydrogen combine, they fall,
metaphorically speaking, from a definite height. We cannot go very far