That and computed from the law of fall become farther and farther removed from the values of and computed from the Brownian movements, the smaller these particles appear to be, is just what would be expected if the particles under consideration have surface impurities or non-spherical shapes or else are not mercury at all.[124] If, further, exact multiple relations hold for them, as at least a dozen of us, including Dr. Ehrenhaft himself, now find that they invariably do, there is scarcely any other interpretation possible except that of incorrect assumptions as to density.[see footnote 124] Again, the fact that these data are all taken when the observers are working with the exceedingly dense substances, mercury and gold, volatilized in an electric arc, and when, therefore, anything not mercury or gold, but assumed to be, would yield very low values of and , is in itself a very significant circumstance. The further fact that Dr. Ehrenhaft implies that normal values of e very frequently appear in his work,[125] while these low erratic drops represent only a part of the data taken, is suggestive. When one considers, too, that in [Pg 174] place of the beautiful consistency and duplicability shown in the oil-drop work, Dr. Ehrenhaft and his pupils never publish data on any two particles which yield the same value of , but instead find only irregularities and erratic behavior,[126] just as they would expect to do with non-uniform particles, or with particles having dust specks attached to them, one wonders why any explanation other than the foreign-material one, which explains all the difficulties, has ever been thought of. As a matter of fact, in our work with mercury droplets, we have found that the initial rapid evaporation gradually ceases, just as though the droplets had become coated with some foreign film which prevents further loss. Dr. Ehrenhaft himself, in speaking of the Brownian movements of his metal particles, comments on the fact that they seem at first to show large movements which grow smaller with time.[127] This is just what would happen if the radius were increased by the growth of a foreign film.