There are likewise produced, at the expense of the gas still subsisting after rarefication within the tube, positive ions which, attracted by the cathode and reaching it, are not all neutralised by the negative electrons, and can, if the cathode be perforated, pass through it, and if not, pass round it.

We have then what are called the canal rays of Goldstein, which are deviated by an electric or magnetic field in a contrary direction to the cathode rays; but, being larger, give weak deviations or may even remain undeviated through losing their charge when passing through the cathode.
It may also be the parts of the walls at a distance from the cathode which send a positive rush to the latter, by a similar mechanism.

It may be, again, that in certain regions of the tube cathode rays are met with diffused by some solid object, without having thereby changed their nature.

All these complexities have been cleared up by M.
Villard, who has published, on these questions, some remarkably ingenious and particularly careful experiments.
M.Villard has also studied the phenomena of the coiling of the rays in a field, as already pointed out by Hittorf and Pluecker.

When a magnetic field acts on the cathode particle, the latter follows a trajectory, generally helicoidal, which is anticipated by the theory.
We here have to do with a question of ballistics, and experiments duly confirm the anticipations of the calculation.