re the key to half the mysteries of matter. Electrons in
rapid motion, as we shall see, explain what we mean by an "electric
current," not so long ago regarded as one of the most mysterious
manifestations in nature.

"What a wonder, then, have we here!" says Professor R. K. Duncan. "An
innocent-looking little pinch of salt and yet possessed of special
properties utterly beyond even the fanciful imaginings of men of past
time; for nowhere do we find in the records of thought even the hint of
the possibility of things which we now regard as established fact. This
pinch of salt projects from its surface bodies [i.e. electrons]
possessing the inconceivable velocity of over 100,000 miles a second, a
velocity sufficient to carry them, if unimpeded, five times around the
earth in a second, and possessing with this velocity, masses a thousand
times smaller than the smallest atom known to science. Furthermore,
they are charged with negative electricity; they pass straight through
bodies considered opaque with a sublime indifference to the properties
of the body, with the exception of its mere density; they cause bodies
which they strike to shine out in the dark; they affect a photographic
plate; they render the air a conductor of electricity; they cause clouds
in moist air; they cause chemical action and have a peculiar
physiological action. Who, to-day, shall predict the ultimate service to
humanity of the beta-rays from radium!"

Sec. 6

THE ELECTRON THEORY, OR THE NEW VIEW OF MATTER

The Structure of the Atom

There is general agreement amongst all chemists, physicists, and
mathematicians upon the conclusions which we have so far given. We know
that the atoms of matter are constantly--either spontaneously or under
stimulation--giving off electrons, or breaking up into electrons; and
they therefore contain electrons. Thus we have now complete proof of the
independent existence of atoms and also of electrons.

When, however, the man of science tries to tell us _how_ electrons
compose atoms, he passes from facts to speculation, and very difficult
speculation. Take the letter "o" as it is printed on this page. In a
little bubble of hydrogen gas no larger than that letter there are
_trillions_ of atoms; and they are not packed together, but are
circulating as freely as dancers in a ball-room. We are asking the
physicist to take one of these minute atoms and tell us how the still
smaller electrons are arranged in it. Natur