Faure improved the Plante cell by adding a paste of red lead or
minium (Pb204) and dilute sulphuric acid (H2SO4), by which a large
quantity of peroxide and spongy lead could be formed on the
plates. Sellon and Volckmar increased its efficiency by putting
the paste into holes cast in the lead. The "E. P. S." accumulator
of the Electrical Power Storage Company is illustrated in figure
21, and consists of a glass or teak box containing two sets of
leaden grids perforated with holes, which are primed with the
paste and steeped in dilute sulphuric acid. Alternate grids are
joined to the poles of a charging battery or generator, those
connected to the positive pole being converted into peroxide of
lead and the others into spongy lead. The terminal of the peroxide
plates, being the positive pole of the accumulator, is painted
red, and that of the spongy plates or negative pole black.
Accumulators of this kind are highly useful as reservoirs of
electricity for maintaining the electric light, or working
electric motors in tramcars, boats, and other carriages.





CHAPTER III.

THE ELECTRICITY OF HEAT.


In the year 1821 Professor Seebeck, of Berlin, discovered a third
source of electricity. Volta had found that two dissimilar metals