208 Messrs. Mendenhall §• Ingersoll on Phenomena 
of these is observed when a small particle of cobalt, say, is 
placed on the surface of a glower carrying a direct current. 
When the temperature is raised to about 1200° G. it will 
commence a slow and regular end-over-end rolling motion 
along the glower, which changes in direction when the 
current is reversed, and which is not affected by holding the 
glower vertical, or, indeed, by turning it completely upside 
down. It is regretted that a somewhat careful study of this 
and the allied phenomena has not led as yet to as definite 
and satisfactory an explanation of the cause as might be 
desired ; although of course it may be said at once that, as 
the glower is an electrolytic conductor, such motions are 
probably related to the other, and little understood, motions 
of matter in an electrolyte which have been observed many 
times (see discussion in Winkelmann) although the connexion 
is not very obvious. Our observations and such conclusions 
as we have been able to draw may not, however, be without 
interest, and will be discussed under two heads corresponding 
to two distinct, although evidently related, effects which have 
been observed, namely : — 
(a) A rolling or sliding of molten globules of metal on the 
surface of the glower. 
(b) A motion of solid particles of metals and their oxides. 
This is the curious end-over-end rolling above-mentioned 
which will take place with particles of the most irregular 
shape. 
Case a. — A rolling or sliding of molten globules of 
metal has been observed with most of the metals which will 
melt into a globule on the glower ; rhodium perhaps showing 
it the best. The motion may be slow and accompanied by a 
plowing up of the surface of the glower as if the globule were 
trying to embed itself, or — and this is especially true just 
when the substance is first melted — it may be as fast as the 
eye can follow. In direction * it may be either with or 
against the current, according to the metal used, and in every 
case where both can be observed agrees as to direction with 
the motion in the solid state described below (Case b). With 
gold and platinum the motion is with the current. This 
rolling is very possibly similar, as to cause, to an effect noted, 
we believe by Quincke, in which a globule of mercury placed 
in a tube of acidulated water is observed to move rapidly, 
only in this case against the current. 
* This rolling has also heen observed, in the same direction, with 
rhodium on special glowers composed of MgO and Al o 3 , instead of the 
oxides of ziroonium and yttrium as is the case with commercial glowers ; 
so that it does not depend on the special constitution of the glower. 
