repeat
this process as many times as it is necessary to obtain a certain
thickness of coating. On the point of the coated filament I form a
button in the same manner.

There is no doubt that such a button--properly prepared under great
pressure--of carborundum, especially of powder of the best quality,
will withstand the effect of the bombardment fully as well as anything
we know. The difficulty is that the binding material gives way, and
the carborundum is slowly thrown off after some time. As it does not
seem to blacken the globe in the least, it might be found useful for
coating the filaments of ordinary incandescent lamps, and I think that
it is even possible to produce thin threads or sticks of carborundum
which will replace the ordinary filaments in an incandescent lamp. A
carborundum coating seems to be more durable than other coatings, not
only because the carborundum can withstand high degrees of heat, but
also because it seems to unite with the carbon better than any other
material I have tried. A coating of zirconia or any other oxide, for
instance, is far more quickly destroyed. I prepared buttons of diamond
dust in the same manner as of carborundum, and these came in
durability nearest to those prepared of carborundum, but the binding
paste gave way much more quickly in the diamond buttons: this,
however, I attributed to the size and irregularity of the grains of
the diamond.

It was of interest to find whether carborundum possesses the quality
of phosphorescence. One is, of course, prepared to encounter two
difficulties: first, as regards the rough product, the "crystals,"
they are good conducting, and it is a fact that conductors do not
phosphoresce; second, the powder, being exceedingly fine, would not be
apt to exhibit very prominently this quality, since we know that when
crystals, even such as diamond or ruby, are finely powdered, they lose
the property of phosphorescence to a considerable degree.

The question presents itself here, can a conductor phosphoresce? What
is there in such a body as a metal, for instance, that would deprive
it of the quality of phosphorescence, unless it is that property which
characterizes it as a conductor? for it is a fact that most of the
phosphorescent bodies lose that quality when they are sufficiently
heated to become more or less conducting. Then, if a metal be in a
large measure, or perhaps entirely, deprived of that property, it
should be capable of phosphores