The measurement of these deviations will then permit this speed and this relation to be ascertained.
Other processes may be used which all give the same two quantities by two suitably chosen measurements.

Such are the radius of the curve taken by the trajectory of the pencil in a perpendicular magnetic field and the measure of the fall of potential under which the discharge takes place, or the measure of the total quantity of electricity carried in one second and the measure of the calorific energy which may be given, during the same period, to a thermo-electric junction.

The results agree as well as can be expected, having regard to the difficulty of the experiments; the values of the speed agree also with those which Professor Wiechert has obtained by direct measurement.
The speed never depends on the nature of the gas contained in the Crookes tube, but varies with the value of the fall of potential at the cathode.

It is of the order of one tenth of the speed of light, and it may rise as high as one third.

The cathode particle therefore goes about three thousand times faster than the earth in its orbit.
The relation is also invariable, even when the substance of which the cathode is formed is changed or one gas is substituted for another.