Other ions are thus born, and this production is in part compensated for by recombinations between ions of opposite signs.

The impacts will be more active in the event of the gas being placed in a field of force and of the pressure being slight, the speed attained being then greater and allowing the active force to reach a high value.

The energy necessary for the production of an ion is, in fact, according to Professor Rutherford and Professor Stark, something considerable, and it much exceeds the analogous force in electrolytic decomposition.
It is therefore in tubes of rarefied gas that this ionisation by impact will be particularly felt.

This gives us the reason for the aspect presented by Geissler tubes.

Generally, in the case of discharges, new ions produced by the molecules struck come to add themselves to the electrons produced, as will be seen, by the cathode.
A full discussion has led to the interpretation of all the known facts, and to our understanding, for instance, why there exist bright or dark spaces in certain regions of the tube.