from the non-radio-active thorium."*11*

If Professor Thompson's view be correct, the amount of potential energy
inherent in the atom must be enormous.

RADIO-ACTIVITY AND THE STRUCTURE OF THE ATOM

But whatever the source of the energy displayed by the radio-active
substances, it is pretty generally agreed that the radio-activity of
the radio-elements results in the disruption of their atoms. Since all
substances appear to be radio-active in a greater or less degree,
it would seem that, unless there be a very general distribution
of radio-active atoms throughout all substances, all atoms must be
undergoing disruption. Since the distribution of radio-active matter
throughout the earth is so great, however, it is as yet impossible to
determine whether this may not account for the radio-activity of all
substances.

As we have just seen, recent evidence seems to point to the cause of the
disruption of radio-active atoms as lying in the atoms themselves. This
view is quite in accord with modern ideas of the instability of certain
atoms. It has been suggested that some atoms may undergo a slower
disintegration without necessarily throwing off part of their systems
with great velocity. It is even possible that all matter may be
undergoing transformation, this transformation tending to simplify
and render more stable the constituents of the earth. The radio-active
bodies, however, are the only ones that have afforded an opportunity for
studying this transformation. In these the rapidity of the change would
be directly proportionate to their radioactivity. Radium, according
to the recent estimate of the Curies, would be disintegrating over
a million times more rapidly than uranium. Since the amount of
transformation occurring in radium in a year amounts to from 1-2000
to 1-10,000 of the total amount, the time required for the complete
transformation of an atom of uranium would be somewhere between two
billion and ten billion years--figures quite beyond the range of human
comprehension.

Various hypotheses have been postulated to account for the instability
of the atom. Perhaps the most thinkable of these to persons not
specially trained in dealing with abstruse subjects is that of Professor
Thompson. It has the additional merit, also, of coming from one of the
best-known investigators in this particular field. According to this
hypothesis the atom may be considered as a mass of positively and
negatively charged particl