is now known.
Now we know from methods which have nothing to do with the electromagnetic theory of the origin of mass, that the excessive minuteness predicted by that theory for both the positive and the negative constituents of atoms is in fact correct, though we have no evidence as to whether the foregoing ratio is right.
III. DIRECT EXPERIMENTAL PROOF OF THE EXCESSIVE MINUTENESS OF THE ELECTRONIC CONSTITUENTS OF ATOMS
For at least twenty years we have had direct experimental proof[139] that the fastest of the
-particles, or helium atoms, which are ejected by radium, shoot in practically straight lines through as much as 7 cm. of air at atmospheric pressure before being brought to rest. This distance is then called the “range” of these
-rays. Figs. [14] and [15] show actual photographs of the tracks of such particles. We know too, for the reasons given on [p. 139], that these