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NEGATIVELY CHARGED PARTICLES 39

molecule. To do this requires the expenditure of a definite
amount of work which has to be done on the corpuscle by the
particle. The energy communicated to the corpuscle depends
on the velocity of the particle, and unless this velocity reaches
a definite value the corpuscle will not get enough energy to
escape from the molecule and will thus be unable to neutralize
the particle.

NEGATIVELY CHARGED PARTICLES.

We have already seen (p. 18) that besides the particles
which cany a positive charge of electricity there are others
which carry a ' negative one. These negatively charged
particles show many analogies with the particles which produce
the secondary rays we have been considering. Like them they
are particles which have changed their condition after passing
through the cathode. Before passing through the cathode
they were positively charged and they owe the high velocity
they possess to the action on this charge of the electric field in
front of the cathode. After passing through the cathode they
get neutralized and then attract to themselves a negatively
electrified corpuscle which gives them a negative charge. The
attraction which brings the corpuscle and the particle together
is the attraction between a neutral particle and a corpuscle.
We may imagine that this attraction is the result of electrostatic
induction between the charge on the corpuscle and the
particle. The magnitude of this attraction will depend upon
how nearly the particle behaves like a conductor of electricity,
or perhaps more accurately like a body of very great specific
inductive capacity. The greater the specific inductive capacity
the greater the attraction, while if the specific inductive capacity
Is the same as that of the surrounding medium there will be
no attraction at all. It is not surprising therefore to find



	*NEGATIVELY* CHARGED PARTICLES 39 molecule. To do this requires the expenditure of a definite amount of work which has to be done on the corpuscle by the particle. The energy communicated to the corpuscle depends on the velocity of the particle, and unless this velocity reaches a definite value the corpuscle will not get enough energy to escape from the molecule and will thus be unable to neutralize the particle. NEGATIVELY CHARGED PARTICLES. We have already seen (p. 18) that besides the particles which cany a positive charge of electricity there are others which carry a ' negative one. These negatively charged particles show many analogies with the particles which produce the secondary rays we have been considering. Like them they are particles which have changed their condition after passing through the cathode. Before passing through the cathode they were positively charged and they owe the high velocity they possess to the action on this charge of the electric field in front of the cathode. After passing through the cathode they get neutralized and then attract to themselves a negatively electrified corpuscle which gives them a negative charge. The attraction which brings the corpuscle and the particle together is the attraction between a neutral particle and a corpuscle. We may imagine that this attraction is the result of electrostatic induction between the charge on the corpuscle and the particle. The magnitude of this attraction will depend upon how nearly the particle behaves like a conductor of electricity, or perhaps more accurately like a body of very great specific inductive capacity. The greater the specific inductive capacity the greater the attraction, while if the specific inductive capacity Is the same as that of the surrounding medium there will be no attraction at all. It is not surprising therefore to find