es, all in rapid motion, their mutual forces
holding them in equilibrium. In case of a very complex structure of
this kind it is possible to conceive of certain particles acquiring
sufficient kinetic energy to be projected from the system. Or the
constraining forces may be neutralized momentarily, so that the particle
is thrown off at the same velocity that it had acquired at the instant
it is released. The primary cause of this disintegration of the atom
may be due to electro-magnetic radiation causing loss of energy of the
atomic system.

Sir Oliver Lodge suggests that this instability of the atom may be the
result of the atom's radiation of energy. "Lodge considered the simple
case of a negatively charged electron revolving round an atom of
mass relatively large but having an equal positive charge and held in
equilibrium by electrical forces. This system will radiate energy, and
since the radiation of energy is equivalent to motion in a resisting
medium, the particle tends to move towards the centre and its speed
consequently increases. The rate of radiation of energy will increase
rapidly with the speed of the electron. When the speed of the electron
becomes very nearly equal to the velocity of light, according to Lodge,
the system is unstable. It has been shown that the apparent mass of an
electron increases very rapidly as the speed of light is approached, and
is theoretically infinite at the speed of light. There will be at this
stage a sudden increase of the mass of the revolving atom, and, on the
supposition that this stage can be reached, a consequent disturbance of
the balance of forces holding the system together. Lodge considers it
probable that under these conditions the parts of the system will break
asunder and escape from the sphere of one another's influence.

"It is probable," adds Rutherford, "that the primary cause of the
disintegration of the atom must be looked for in the 1 ss of energy of
the atomic system due to electro-magnetic radiation."*12*

Several methods have been devised for testing the amount of heat given
off by radium and its compounds, and for determining its actual rise
in temperature above that of the surrounding atmosphere. One of these
methods is to place some substance, such as barium chloride, in a
calorimeter, noting at what point the mercury remains stationary. Radium
is then introduced, whereupon the mercury in the tube gradually rises,
falling again when the radium is rem