In subsequent experiments it will be found almost impossible to produce further condensation of vapour.
But these forces may also be of electrical origin.

Von Helmholtz long since showed that electricity exercises an influence on the condensation of the vapour of water, and Mr C.T.R.Wilson, with this view, has made truly quantitative experiments.

It was rapidly discovered after the apparition of the X rays that gases that have become conductors, that is, ionised gases, also facilitate the condensation of supersaturated water vapour.
We are thus led by a new road to the belief that electrified centres exist in gases, and that each centre draws to itself the neighbouring molecules of water, as an electrified rod of resin does the light bodies around it.

There is produced in this manner round each ion an assemblage of molecules of water which constitute a germ capable of causing the formation of a drop of water out of the condensation of excess vapour in the ambient air.

As might be expected, the drops are electrified, and take to themselves the charge of the centres round which they are formed; moreover, as many drops are created as there are ions.