had been in the hands of a gardener and of laborers, who were without
previous knowledge of electricity, and the only repairs that had been
found necessary were one renewal of the commutators and an occasional
change of metallic contact brushes.

An interesting application of electric transmission to cranes, by Dr.
Hopkinson, was shown in operation.

Among the numerous other applications of the electrical transmission
of power, that to electrical railways, first exhibited by Dr. Werner
Siemens, at the Berlin Exhibition of 1879, had created more than
ordinary public attention. In it the current produced by the dynamo
machine, fixed at a convenient station and driven by a steam engine
or other motor, was conveyed to a dynamo placed upon the moving car,
through a central rail supported upon insulating blocks of wood, the two
working rails serving to convey the return current. The line was 900
yards long, of 2 ft gauge, and the moving car served its purpose of
carrying twenty visitors through the exhibition each trip. The success
of this experiment soon led to the laying of the Lichterfelde line, in
which both rails were placed upon insulating sleepers, so that the one
served for the conveyance of the current from the power station to the
moving car, and the other for completing the return circuit. This line
had a gauge of 3 ft. 3 in., was 2,500 yards in length, and was worked
by two dynamo machines, developing an aggregate current of 9,000 watts,
equal to 12 horse power. It had now been in constant operation since May
16, 1881, and had never failed in accomplishing its daily traffic.
A line half a kilometer in length, but of 4 ft. 81/2 in. gauge was
established by the lecturer at Paris in connection with the Electric
Exhibition of 1881. In this case, two suspended conductors in the form
of hollow tubes with a longitudinal slit were adopted, the contact being