ic steamer." When Faure,
having in 1880 improved upon the storage battery of Plante, sent his
four-cell battery from Paris to Glasgow, carrying in it stored
electrical energy, it was found to contain power equal to close upon a
million foot-pounds, which is about the work done by a horse-power
during the space of half an hour. This battery weighed very nearly 75
lb. It nevertheless represented an immense forward step in the problem
of compressing a given quantity of potential power into a small weight
of accumulator.

The progress made during less than twenty years to the end of the
century may be estimated from the conditions laid down by the
Automobile Club of Paris for the competitive test of accumulators
applicable to auto-car purposes in 1899. It was stipulated that five
cells, weighing in all 244 lb., should give out 120 ampere-hours of
electric intensity; and that at the conclusion of the test there
should remain a voltage of 1.7 volt per cell.

Very great improvements in the construction of electric accumulators
are to be looked for in the near future. Hitherto the average duration
of the life of a storage cell has not been more than about two years;
and where impurities have been present in the sulphuric acid, or in
the litharge or "minium" employed, the term of durability has been
still further shortened. It must be remembered that while the
principal chemical and electrical action in the cell is a circular
one,--that is to say, the plates and liquids get back to the original
condition from which they started when beginning work in a given
period,--there is also a progressive minor action depending upon the
impurities that may be present. Such a reagent, for instance, as
nitric acid has an extremely injurious effect upon the plates.

During the first decade after Plante and Faure had made their original
discoveries, the main drawback to the advancement of the electric
accumulator for the storage of power owed its existence to the lack of
precise knowledge, among those placed in charge of storage batteries,
as to the destructive effects of impurities in the cells. It is,
however, now the rule that all acids and all samples of water used for
the purpose must be carefully tested before adoption, and this
practice, in itself, has greatly prolonged the average life of the
accumulator cell.

The era of the large electric accumulator of the kind foreshadowed by
Prof. Sylvanus P. Thompson has not yet arrived, the