There is thus produced a current due to the transport to the electrodes of the charges which existed on the ions.
If the gas thus ionised be left to itself, in the absence of any electric field, the ions, yielding to their mutual attraction, must finally meet, combine, and reconstitute a neutral molecule, thus returning to their initial condition.

The gas in a short while loses the conductivity which it had acquired; or this is, at least, the phenomenon at ordinary temperatures.

But if the temperature is raised, the relative speeds of the ions at the moment of impact may be great enough to render it impossible for the recombination to be produced in its entirety, and part of the conductivity will remain.
Every element of volume rendered a conductor therefore furnishes, in an electric field, equal quantities of positive and negative electricity.

If we admit, as mentioned above, that these liberated quantities are borne by ions each bearing an equal charge, the number of these ions will be proportional to the quantity of electricity, and instead of speaking of a quantity of electricity, we could use the equivalent term of number of ions.

For the excitement produced by a given pencil of X rays, the number of ions liberated will be fixed.
Thus, from a given volume of gas there can only be extracted an equally determinate quantity of electricity.
The conductivity produced is not governed by Ohm's law.