We can also obtain other information regarding ions: we can ascertain,
for instance, their velocities, and also get an idea of their order of
magnitude.
By treating the speeds possessed by the liberated charges as
components of the known speed of a gaseous current, Mr Zeleny measures
the mobilities, that is to say, the speeds acquired by the positive
and negative charges in a field equal to the electrostatic unit. He
has thus found that these mobilities are different, and that they
vary, for example, between 400 and 200 centimetres per second for the
two charges in dry gases, the positive being less mobile than the
negative ions, which suggests the idea that they are of greater
mass.[30]
[Footnote 30: A full account of these experiments, which were executed
at the Cavendish Laboratory, is to be found in _Philosophical
Transactions_, A., vol. cxcv. (1901), pp. 193 et seq.--ED.]
M. Langevin, who has made himself the eloquent apostle of the new
doctrines in France, and has done much to make them understood and
admitted, has personally undertaken experiments analogous to those of
M.
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