ty of
accurately determining the number of alpha particles expelled from
radium per second."--ED.]

[Footnote 42: See Rutherford, op. cit. p. 150.--ED.]

If radium transforms itself in such a way that its activity does not
persist throughout the ages, it loses little by little the provision
of energy it had in the beginning, and its properties furnish no valid
argument to oppose to the principle of the conservation of energy. To
put everything right, we have only to recognise that radium possessed
in the potential state at its formation a finite quantity of energy
which is consumed little by little. In the same manner, a chemical
system composed, for instance, of zinc and sulphuric acid, also
contains in the potential state energy which, if we retard the
reaction by any suitable arrangement--such as by amalgamating the zinc
and by constituting with its elements a battery which we cause to act
on a resistance--may be made to exhaust itself as slowly as one may
desire.

There can, therefore, be nothing in any way surprising in the fact
that a combination which, like the atomic combination of radium, is
not stable--since it disaggregates itself,--is capable of
spontaneously liberating energy, but what may be a little astonishing,
at first sight, is the considerable amount of this energy.

M. Curie has calculated directly, by the aid of the calorimeter, the
quantity of energy liberated, measuring it entirely in the form of
heat. The disengagement of heat accounted for in a grain of radium is
uniform, and amounts to 100 calories per hour. It must therefore be
admitted that an atom of radium, in disaggregating itself, liberates
30,000 times more energy than a molecule of hydrogen when the latter
combines with an atom of oxygen to form a molecule of water.

We may ask ourselves how the atomic edifice of the active body can be
constructed, to contain so great a provision of energy. We will remark
that such a question might be asked concerning cases known from the
most remote antiquity, like that of the chemical systems, without any
satisfactory answer ever being given. This failure surprises no one,
for we get used to everything--even to defeat.

When we come to deal with a new problem we have really no right to
show ourselves more exacting; yet there are found persons who refuse
to admit the hypothesis of the atomic disaggregation of radium because
they cannot have set before them a detailed plan of that complex whole