78 RA YS OF POSITIVE ELECTRICITY

corresponding deflection of the primary shows (seep. 21) that
the swiftest of the particles in the prolongation has twice the
kinetic energy of the swiftest in the primary. Thus these
particles when in the electric field in the discharge tube
acquire twice the kinetic energy of the normal particle; they
must therefore when in the discharge tube have had twice
the normal charge. They must, after passing through the
cathode and before getting into the deflecting fields, have had
their charge reduced to the normal value. For, as we have
seen, the value of ejm in these fields is normal, hence if they
have retained the double charge they must have double the
mass. If, however, they had retained the double charge the
electrostatic deflection would have been normal: for though
the kinetic energy is doubled, which halves the deflection for
normal charge, the charge and therefore the electrostatic
deflection for given kinetic energy is doubled too, and hence
the result would be the normal deflection, while the actual
deflection is only one-half of this. We conclude, therefore,
that the prolongation is due to particles which had a double
charge when in the discharge tube, but which have lost one of
these charges after passing through the cathode.

It is a strong confirmation of this view that when we find
these prolongations we generally find on the same plate para-
bolas with their heads in the normal place giving a value of
ejm twice that given by the line with the prolongation ; these
are due to particles which have retained their double charge
after passing through the cathode. And conversely when the
lines corresponding to the double value of e]m are present
we find a tail or prolongation to the line corresponding to
the normal value. This would not necessarily be true at
pressures so low that the particles did not make any collisions
after passing through the face of the cathode, but I have not
been able to reduce the pressure to this point.