were made on different particles. So far as concerns
, these measurements, as everyone agrees, were essentially cloud measurements like Wilson’s.
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]
The apparent contradiction between these results and mine was explained when Mr. Fletcher and myself showed[110] experimentally that Brownian movements produced just such apparent fluctuations as Ehrenhaft observed when the