powerful electric field drives all of these ions toward a given drop this drop selects in each instance just the charge which corresponds to its particular radius. Such an assumption is not only too grotesque for serious consideration, but it is directly contradicted by my experiments, for I have repeatedly pointed out that with a given value of I obtain exactly the same value of , whether I work with big drops or with little ones. [Pg 177] V. NEW PROOF OF THE CONSTANCY OF For the sake of subjecting the constancy of to the most searching test, I have made new measurements of the same kind as those heretofore reported, but using now a range of sizes which overlaps that in which Dr. Ehrenhaft works. I have also varied through wide limits the nature and density of both the gas and the drops. Fig. 13 (I) contains new oil-drop data taken in air; Fig. 13 (II) similar data taken in hydrogen. The radii of these drops, computed by the very exact method given in the Physical Review[129] vary tenfold, namely, from .000025 cm. to .00023 cm. Dr. Ehrenhaft’s range is from .000008 cm. to .000025 cm. It will be seen that these drops fall in every instance on the lines of Fig. 13, I and II, and hence that they all yield exactly the same value of , namely, . The details of the measurements, which are just like those previously given, will be entirely omitted. There is here not a trace of an indication that the value of “” becomes smaller as “” decreases. The points on these two curves represent consecutive series of observations, not a single drop being omitted in the case of either the air or the hydrogen. This shows the complete uniformity and consistency which we have succeeded in obtaining in the work with oil drops.