But it will be well to trace the whole action. The electric
current may be obtained by means of Plante secondary cells charged by
Daniell's cells--in other words, one or two Daniell's cells are
constantly in action charging three or six Plante cells, and it is the
Plante cells that are called into action to electrify the magnet. The
battery is carried in a box in the brake van. The engineers, however,
seem to prefer that the current be obtained by means of a small Gramme
machine, driven direct by a Brotherhood three-cylinder engine, the
steam for which is obtained from the locomotive. The velocity and
hence the current of the Gramme machine can be regulated, and so the
action of the brakes. M. Achard prefers the Plante cells; he informs
us that he has tried the Faure battery, but the results obtained were
not satisfactory. The regulator, R squared, consists of a cylinder of wood
around which, as shown, wire is wound. The length of this wire in the
circuit, increasing as it does the resistance of the circuit,
determines the current to the electro-magnet. The action is as
follows: When it is necessary to apply the brakes, a simple pressure
of a key or the turn of a handle sends the electric current into the
wires of the electro-magnet. An attraction immediately takes place,
and the poles and armatures are brought into contact.
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