shown by Small Particles on a Nernst Glower. 211 
example glass or common salt), or require too high a tempe- 
rature (for example MgO). The phenomena were, however, 
readily produced on a glower made of pure zirconium oxide. 
No motion will occur over a thin layer of MgO coated on a 
glower surface, — probably because under these circumstances 
the MgO carries practically no current. 
(7) A particle of a given metal moves with difficulty if 
at all over a part of the glower which has been fluxed* with 
the same metal. The motion of another metal over this part 
of the surface is in general not so much altered by this 
fluxing of the first. Heating for a short time at a high 
temperature will remove these effects produced by the 
fluxing in of any metal, probably because the metal is 
vaporized off in this process. 
(8) Placing the glower in an atmosphere of C0 2 or in a one- 
millimetre vacuum does not perceptibly alter the effect. Nor 
does a jet of oxygen blown at the glower or particle make 
any difference, unless it be strong enough to cool the particle 
considerably, especially at its point of contact with the 
glower. 
(9) Oxides iof many metals (see Table, p. 212) show a 
similar motion. 
(10) In the table the approximate atomic weights of 
zirconium and yttrium (whose oxides are the principal con- 
stituents of the glower) are inserted, and it will be noted 
that, with two exceptions (boron and ruthenium) , all metals 
having an atomic weight greater than these metals move with 
the current, and those with lower atomic weights move against 
the current. In order to test further this rather striking, but 
probably accidental arrangement, we have made many attempts 
to observe the motion on glowers made of oxides of metals 
having much smaller atomic weights — especially MgO and 
A1 2 3 — in order to see whether the motion of cobalt, for 
example, would be reversed on such a glower. So far we 
have been entirely unsuccessful in observing anything but 
the motion of molten globules (above referred to) on such a 
glower, and the metals which make molten globules have 
almost all higher atomic weights than the zirconium of the 
ordinary glower, so no reversal would be expected in this 
case. But this negative result is by no means conclusive, 
for, in the first place, it is extremely difficult to make a 
glower of Mg and Al oxides which will run on direct current 
* With most metals (the less oxidizable metals such as gold, platinum, 
rhodium, and iridium are exceptions) heating to a sufficiently high 
temperature results in the metal soaking into and fluxing witb the 
glower material. 
