came out differently, even for drops showing the same velocity under gravity.” In the Brownian-movement work no such precautions to obtain dust-free air had been taken because we wished to test the general validity of equations (28) and (29). That we actually used in this test two particles which had a mean density very much smaller than that of oil and one which was considerably too heavy, was fortunate since it indicated that our result was indeed independent of the material used.
It is worthy of remark that in general, even with oil drops, almost all of those behaving abnormally fall too slowly, that is, they fall below the line of [Fig. 5] and only rarely does one fall above it. This is because the dust particles which one is likely to observe, that is, those which remain long in suspension in the air, are either in general lighter than oil or else expose more surface and hence act as though they were lighter. When one works with particles made of dense metals this behavior will be still more marked, since all surface impurities of whatever sort will diminish the density. The possibility, however, of freeing oil-drop experiments from all such sources of error is shown by the fact that although during the year 1915-16 I studied altogether as many as three hundred drops, there was not one which did not fall within less than 1 per cent of the line of [Fig. 5]. It will be shown, too, in this chapter, that in spite of the failure of the Vienna experimenters, it is possible under suitable conditions to obtain mercury drops which behave, even as to law of fall, in practically all cases with perfect consistency and normality.
When E. Weiss in Prag and K. Przibram in the Vienna laboratory itself, as explained in [chap. VII], had found that
for all the substances which they worked with, including silver particles like those used by Ehrenhaft, gave about the right value of
, although yielding much too low values of
when the latter was computed from the law of fall of silver particles, the scientific world practically universally accepted our explanation of Ehrenhaft’s results and ceased to concern itself with the idea of a sub-electron.[113]
In 1914 and 1915, however, Professor Ehrenhaft[114] and two of his pupils, F. Zerner[115] and D. Konstantinowsky,[116] published new evidence for the existence of such a sub-electron and the first of these authors has kept up some discussion of the matter up to the present. These experimenters make three contentions. The first is essentially that they have now determined