pposes that metals tend, as it were, to vaporize when in
presence of a liquid. A piece of zinc introduced, for example, into
pure water gives birth to a few metallic ions. These ions become
positively charged, while the metal naturally takes an equal charge,
but of contrary sign. Thus the solution and the metal are both
electrified; but this sort of vaporization is hindered by
electrostatic attraction, and as the charges borne by the ions are
considerable, an equilibrium will be established, although the number
of ions which enter the solution will be very small.

If the liquid, instead of being a solvent like pure water, contains an
electrolyte, it already contains metallic ions, the osmotic pressure
of which will be opposite to that of the solution. Three cases may
then present themselves--either there will be equilibrium, or the
electrostatic attraction will oppose itself to the pressure of
solution and the metal will be negatively charged, or, finally, the
attraction will act in the same direction as the pressure, and the
metal will become positively and the solution negatively charged.
Developing this idea, Professor Nernst calculates, by means of the
action of the osmotic pressures, the variations of energy brought into
play and the value of the differences of potential by the contact of
the electrodes and electrolytes. He deduces this from the
electromotive force of a single battery cell which becomes thus
connected with the values of the osmotic pressures, or, if you will,
thanks to the relation discovered by Van t' Hoff, with the
concentrations. Some particularly interesting electrical phenomena
thus become connected with an already very important group, and a new
bridge is built which unites two regions long considered foreign to
each other.

The recent discoveries on the phenomena produced in gases when
rendered conductors of electricity almost force upon us, as we shall
see, the idea that there exist in these gases electrified centres
moving through the field, and this idea gives still greater
probability to the analogous theory explaining the mechanism of the
conductivity of liquids. It will also be useful, in order to avoid
confusion, to restate with precision this notion of electrolytic ions,
and to ascertain their magnitude, charge, and velocity.

The two classic laws of Faraday will supply us with important
information. The first indicates that the quantity of electricity
passing through the liquid