An apparatus for generating high potential difference by the escape of
steam through proper nozzles.

It consists of a boiler mounted on four glass legs or otherwise
insulated. An escape pipe terminates in a series of outlets so shaped as
to impede the escape of the steam by forcing it out of the direct
course. These jets are lined with hard wood. They are enclosed in or led
through a box which is filled with cold water.

This is to partly condense the steam so as to get it into the vesicular
state, which is found essential to its action. Dry steam produces no
excitation. If the boiler is fired and the steam is permitted to escape
under the above conditions the vesicles presumably, or the “steam” is
found to be electrified. A collecting comb held against the jet becomes
charged and charges any connected surface.

The boiler in the above case is negatively and the escaping “steam” is
positively charged. By changing the material of the linings of the jets,
or by adding turpentine the sign of the electricity is reversed. If the
water contains acid or salts no electricity is produced. The regular
hydro-electric machine is due to Sir William Armstrong.

Faraday obtained similar results with moist air currents.