He has thus been enabled by working _in vacuo_ to register the very different velocities which, starting in the case of certain rays from about seven-tenths of the velocity of light, attain in other cases to ninety-five hundredths of it.
It is thus noted that the ratio of charge to mass--which for ordinary speeds is constant and equal to that already found by so many experiments--diminishes slowly at first, and then very rapidly when the velocity of the ray increases and approaches that of light.

If we represent this variation by a curve, the shape of this curve inclines us to think that the ratio tends toward zero when the velocity tends towards that of light.
All the earlier experiments have led us to consider that the electric charge was the same for all electrons, and it can hardly be conceived that this charge can vary with the velocity.

For in order that the relation, of which one of the terms remains fixed, should vary, the other term necessarily cannot remain constant.

The experiments of Professor Kaufmann, therefore, confirm the previsions of Max Abraham's theory: the mass depends on the velocity, and increases indefinitely in proportion as this velocity approaches that of light.

These experiments, moreover, allow the numerical results of the calculation to be compared with the values measured.