The electron, its isolation and measurement and the determination of some of its properties
John Stuart Mill · en
In the spring and summer of 1909 I isolated individual water droplets
and determined the charges carried by each one,[105] and in April,
1910, I read before the American Physical Society the full report on
the oil-drop work in which the multiple relations between charges
were established, Stokes’s Law corrected, and accurately
determined.[106] In the following month (May, 1910) Dr. Ehrenhaft,[107]
having seen that a vertical condenser arrangement made possible, as
shown theoretically and experimentally in the 1909 papers mentioned
above, the independent determination of the charge on each individual
particle, read the first paper in which he had used this arrangement
in place of the De Broglie arrangement which he had used theretofore.
He reported results identical in all essential particulars with those
which I had published on water drops the year before, save that where
I obtained consistent and simple multiple relations between charges
carried by different particles he found no such consistency in these
relations. The absolute values of these charges obtained on the
assumption of Stokes’s Law fluctuated about values considerably lower
than . Instead, however, of throwing the burden
upon Stokes’s Law or upon wrong assumptions as to the density of his
particles, he remarked in a footnote that Cunningham’s theoretical
correction to Stokes’s Law,[108] which he (Ehrenhaft) had just seen,
would make his values come still lower, and hence that no failure of
Stokes’s Law could be responsible for his low values. He considered
his results therefore as opposed to the atomic theory of electricity
altogether, and in any case as proving the existence of charges much
smaller than that of the electron.[109]
[Pg 164]