ms together; and that if two grammes of pure electrons
could be placed one centimetre apart they would repel each other with a
force equal to 320 quadrillion tons. The inexpert imagination reels,
but it must be remembered that the speed of the electron is a measured
quantity, and it is within the resources of science to estimate the
force necessary to project it at that speed. [*]

* See Sir J. J. Thomson, "The Corpuscular Theory of Matter"
(1907) and--for a more elementary presentment--"Light
Visible and Invisible" (1911); and Mr. Fournier d'Albe, "The
Electron Theory" (2nd. ed., 1907).

Such are the discoveries of the last fifteen years and a few of the
mathematical deductions from them. We are not yet in a position to say
positively that the atoms are composed of electrons, but it is clear
that the experts are properly modest in claiming only that this is
highly probable. The atom seems to be a little universe in which, in
combination with positive electricity (the nature of which is still
extremely obscure), from 1700 to 300,000 electrons revolve at a speed
that reaches as high as 100,000 miles a second. Instead of being
crowded together, however, in their minute system, each of them has, in
proportion to its size, as ample a space to move in as a single speck of
dust would have in a moderate-sized room (Thomson). This theory not only
meets all the facts that have been discovered in an industrious decade
of research, not only offers a splendid prospect of introducing unity
into the eighty-one different elements of the chemist, but it opens out
a still larger prospect of bringing a common measure into the diverse
forces of the universe.

Light is already generally recognised as a rapid series of
electro-magnetic waves or pulses in ether. Magnetism becomes
intelligible as a condition of a body in which the electrons revolve
round the atom in nearly the same plane. The difference between positive
and negative electricity is at least partly illuminated. An atom will
repel an atom when its equilibrium is disturbed by the approach of an
additional electron; the physicist even follows the movement of the
added electron, and describes it revolving 2200 billion times a second
round the atom, to escape being absorbed in it. The difference between
good and bad conductors of electricity becomes intelligible. The atoms
of metals are so close together that the roaming electrons pass freely
from one atom t