e hope will mark a great step in advance in
the economic production of electricity.

The distinguishing feature of this battery is that the electrolyte is
not employed as a mobile liquid, but in a quasi-solid form, and it is,
therefore, named dry gas battery. It consists of a number of elements,
which are formed of a porous diaphragm of a non-conducting material
(in this instance plaster of Paris), which is impregnated with dilute
sulphuric acid. Both sides of this diaphragm are covered with very
fine platinum leaf perforated with very numerous small holes, and over
this a thin film of platinum black. Both these coatings are in contact
with frameworks of lead and antimony, insulated one from the other,
which conduct the electricity to the poles of the battery.

A number of these elements are placed side by side, with
non-conducting frames intervening, so as to form chambers through
which the hydrogen gas is passed along one side of the element and air
along the other.

This peculiar construction allows us to get a very large amount of
duty from a very small amount of platinum. One of the batteries before
you, consisting of seven elements, with a total effective surface of
half a square meter, contains 21/2 grammes of platinum leaf and 7
grammes of platinum black, a total of 91/2 grammes of platinum, and
produces a current of 2 amperes and 5 volts, or 10 watts, when the
outer resistance is properly adjusted. This current is equal to nearly
50 per cent. of the total energy obtainable from the hydrogen absorbed
in the battery.

In order to maintain a constant current, we have from time to time
(say once an hour) to interchange the gases, so as to counteract the
disturbing influence produced by the transport of the sulphuric acid
gas from one side of the diaphragm to the other. This operation can
easily be performed automatically by a commutator worked by a clock.

The water produced in the battery by the oxidation of the hydrogen is
carried off by the inert gas mixed with the hydrogen, and by the air,
of which we use a certain excess for this purpose. This is important,
as if the platinum black becomes wet, it loses its absorbing power for
the gases almost completely and stops the work of the battery. To
avoid this was in fact the great difficulty in designing a powerful
gas battery, and all previous constructions which employed the
electrolyte as a mobile liquid failed in consequence.

The results obtained by our b