ly penetrating to the very heart of things.

But those persons who have a little more hardihood do not easily
resist the temptation of forming daring generalisations. Thus it will
occur to some that this property, already discovered in many
substances where it exists in more or less striking degree, is, with
differences of intensity, common to all bodies, and that we are thus
confronted by a phenomenon derived from an essential quality of
matter. Quite recently, Professor Rutherford has demonstrated in a
fine series of experiments that the alpha particles of radium cease to
ionize gases when they are made to lose their velocity, but that they
do not on that account cease to exist. It may follow that many bodies
emit similar particles without being easily perceived to do so; since
the electric action, by which this phenomenon of radioactivity is
generally manifested, would, in this case, be but very weak.

If we thus believe radioactivity to be an absolutely general
phenomenon, we find ourselves face to face with a new problem. The
transformation of radioactive bodies can no longer be assimilated to
allotropic transformations, since thus no final form could ever be
attained, and the disaggregation would continue indefinitely up to the
complete dislocation of the atom.[44] The phenomenon might, it is
true, have a duration of perhaps thousands of millions of centuries,
but this duration is but a minute in the infinity of time, and matters
little. Our habits of mind, if we adopt such a conception, will be
none the less very deeply disturbed. We shall have to abandon the idea
so instinctively dear to us that matter is the most stable thing in
the universe, and to admit, on the contrary, that all bodies whatever
are a kind of explosive decomposing with extreme slowness. There is in
this, whatever may have been said, nothing contrary to any of the
principles on which the science of energetics rests; but an hypothesis
of this nature carries with it consequences which ought in the highest
degree to interest the philosopher, and we all know with what alluring
boldness M. Gustave Le Bon has developed all these consequences in his
work on the evolution of matter.[45]

[Footnote 44: This is the main contention of M. Gustave Le Bon in
his work last quoted.--ED.]

[Footnote 45: See last note.--ED.]

There is hardly a physicist who does not at the present day adopt in
one shape or another the ballistic hypothesis. All new facts ar