Insylation in * Vacuum.” don 
some eight years later still, has in many discussions and 
speculations been attributed to the tearing off of portions of 
the solid metallic kathode. But I believe the most modern 
and best experiments * tend rather to show that it consists 
solely or chiefly of atoms of resinous electricity (electrions as 
IT call them). 
§ 4. However this may be, it is quite certain (if we accept 
the atomic theory of electricity as true) that the extraction 
of an electrion from the atom is opposed by a definite 
permanent force which must be overcome before the elec- 
trions can be drawn out. But it may be true, and probably 
is true in many cases of the loss of resinous electricity from 
a solid, that the forces called into play may be great enough 
to tear away the atom, with or without its electrion or 
electrions, out of its place in the solid. This, however, would 
not contribute to the transference of electricity from the 
solid : in other words, Varley’s torrent may contain non- 
electrified particles, or vitreously electrified particles, along 
with his negatively electrified particles which we now believe 
to be atoms of electricity. 
§5. It is conceivable also that an atom may, by electro- 
static force, be extracted from a solid metallic anode : and its 
electrion or electrions left behind in the anode. In this case 
the electric current would consist partially, if not wholly, of 
vitreously electrified particles: but I believe there is no 
experimental evidence in support of this supposition. Perhaps 
there is decisive experimental evidence against it. In the 
case, however, of a liquid anode, or kathode, whether of a 
non-conductive substance such as oil, or conductive such as 
liquid mercury or other melted metal, there is a lifting of 
spray or spindrift from the liquid surface, if the electrostatic 
force is strong enough: and this gives something of an 
electric current of vitreously electrified particles from the 
anode. 
§ 6. To form some idea of the force required to pluck an 
electrion out of an atom of the metal of the kathode in a 
very high vacuum: suppose the vacuum so high that ‘no 
current, nor torrent of sparks, passes between two blunt- 
ended electrodes of thick straight wire, 2, mm. asunder, 
when the difference of potential between them is raised to 
200,000 volts. The electrostatic force between the middles of 
their ends will be approximately uniform through the inter- 
vening space: and will amount to 96,000,000 volts per cm, ; 
* J. J. Thomson, ‘ Conduction of Electricity through Gases,’ §§ 50, 
279; and ‘ Electricity and Matter,’ pp. 86, 87.° 
