have a body of only 0.001 meter in thickness, their greater thickness being
due only to the deposit of compressed lead. The rod which fixes the plate
to each pole (Fig. 2) is formed of a special alloy of lead and antimony,
not attacked by acid. This gives rigidity to the rod, and hinders it from
binding when the accumulator is taken out of its case. The copper piece
which surmounts it is fitted at its base with an iron cramp, which is fixed
in the lead, and above which is a wide furrow with two grooved parts, which
being immersed in the lead hinders the copper from slipping round under the
action of the screw. The rod is square, and is cast in a single piece.
Against one of its surfaces the ends of the connected plates press flatly
up. A square form has been selected to give more surface for soldering. The
soldering is autogenous (as in the lead chambers at vitriol works). The
soldering, as well as the entire plates, is entirely immersed in the
liquid, and to prevent any leakage an insulating varnish, perfectly proof
against the acid and the current, is laid over the rod from the part
soldered upward.

[Illustration: FIG. 2.]

If it is wished to lift the accumulator from its chest for any
verification, hooks passing between the plates seize hold of the rods, and
thanks to the rigidity of the antimony lead, they effect the removal of the
apparatus without bending the rods in the least. All the parts of the
plates must be kept at exactly the same reciprocal distances, and a
difference of only 0.001 meter between two points is sufficient to affect
the yield considerably. For an insulating material, wood, when plunged in
dilute acid, is preferred by the inventor. He makes a comb of wood, the
teeth of which vary according to the thickness of the plates to be lodged
between them. Fig. 3 represents a comb having 15/10 of a millimeter for the
negative plates and 25/10 for the positive plates.