ng. So the coefficient of restitution is now
comparable with that of accumulators of the Plante type.

The following are the principal numerical data of the new zinc
accumulator.

PHYSICAL DATA.

E. Electromotive force. 2.36 volts.
R. Mean resistance. 0.02 ohm.
I. Normal intensity of the discharge current. 25 amperes.
i. Intensity of the charge current. 5 to 10 amperes.
Q. Capacity of accumulation after 200 hours' formation. 550,000 couples.

DATA CONCERNING CONSTRUCTION.

Efficient surface of the 4 positive electrodes. 200 square dec.
Efficient surface of the 3 negative electrodes. 15 square dec.
Weight of the positive electrodes. 8.2 kilogrammes.
Weight of the negative electrodes. 1.4 kilogrammes.
Weight of the trough. 2.7 kilogrammes.
Weight of the liquid. 4.4 kilogrammes.
Weight of the attachments. 0.46 kilogrammes.
Weight, total. 17.16 kilogrammes.

The total electric work stored up is 130,000 kilogrammeters, or 7,600
kilogrammeters per kilogramme of accumulator. Theory indicates that a zinc
accumulator might store up as much as 15,600 kilogrammeters per
kilogramme. If the present model gives half less, it is because I have
purposely exaggerated the solidity of the trough and the mass of the
electrodes.

It should be remarked that this capacity of 7,600 kilogrammeters per
kilogramme is much greater than that of any other accumulator constructed
in France. The new model possesses, then, despite the size of the
positives and the box, a relative lightness that will permit it to take a
place upon electric locomotives as well as in fixed installations.

Independently of their use as accumulators, secondary zinc batteries may
be utilized as regulating voltameters in lighting by incandescence, for
deadening piston strokes, attenuating the irregularities in speed, and
covering accidental stoppages.--_E. Reynier, in La Nature._

* * * * *

THE HISTORY OF A LIGHTNING FLASH.

By W. SLINGO.

Lately we have all felt, I doubt not, a considerable amount of interest in
the various phenomena attending this summer's unusually heavy
thunderstorms, accompanied, a