pt 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.

[Illustration: FIG. 3.]

This appliance, which is 0.01 meter in thickness and 0.02 meter in width in
the back, is made very cheaply by machinery. The weight of the accumulator
bears entirely upon the back of the combs, which are all placed back
downward, and the number of which varies according to the size of the
plates. Small combs of wood clasp the plates at their extremities, and make
the entire accumulator quite compact and manageable. The entire accumulator
is shut up in a wooden chest, which the outer teeth of the comb serve to
insulate from the leaden chest, and to prevent any loss of electricity
along the sides.

Fig. 4 shows the arrangement of the side combs. A single glance at this
figure shows that it would be difficult to have more surface without having
recourse to curved, undulated, or folded plates, in which the distances are
variable, and consequently defective. In the Montaud accumulator, the
weight is simply proportional to the intended duration. For the notion, "So
much capacity and so much yield per kilo.," Montaud substitutes the notion,
"So much capacity or yield per square meter, the weight not being taken
into consideration." These Montaud accumulators are classified as follows:
They have from 1 to 12 square meters of surface, and the number
corresponding to the surface indicates its weight of useful lead, its
manner of charging, its capacity, and its manner of discharge.

[Illustration: FIG. 4.]

According to the inventor's experiments, the square meter of active surface
can receive a charging current of 10 amperes, and furnish on discharging a
current of the intensity of 20 amperes. For a "No. 10" accumulator we have
an active surface of 10 square meters, a charging current of 100 amperes,
and on discharging a current of 200 amperes. A square meter of lead of the
thickness of 0.001 meter weighs about 11 kilos.

As both surfaces of the lead are utilized, their weight is reduced to 51/2
kilos. A No. 10 therefore requires 55 kil