depolarization may therefore be considered as costing scarcely
anything. The oxide of copper battery is a durable and valuable
battery, which by its special properties seems likely to replace
advantageously in a great number of applications the batteries at
present in use.

* * * * *




FARCOT'S SIX HORSE POWER STEAM ENGINE.


This horizontal steam engine, recently constructed by Mr. E.D. Farcot
for actuating a Cance dynamo-electric machine, consists of a cast iron
bed frame, A, upon which are mounted all the parts. The two jacketed,
cylinders, B and C, of different diameters, each contains a
simple-acting piston. The two pistons are connected by one rod in
common, which is fixed at its extremity to a cross-head, D, running in
slides, E and F, and is connected with the connecting rod, G. The head
of the latter is provided with a bearing of large diameter which
embraces the journal of the driving shaft, H.

The steam enters the valve-box through the orifice, J, which is
provided with a throttle-valve, L, that is connected with a governor
placed upon the large cylinder. The steam, as shown in Fig. 2 (which
represents the piston at one end of its travel), is first admitted
against the right surface of the small piston, which it causes to
effect an entire stroke corresponding to a half-revolution of the