Having slightly diverged from the original lines by describing a system
which is at present not introduced into Europe, a few remarks on the
subject of electric motors may not be inappropriate, as they are almost
universally worked in the United States, from the installation which
supplies electric light. There is a considerable profit to the electric
company if electric power is taken in the district, the wires conveying
the lighting current are thus economically employed during the day. In
the diagram, Fig. 15, which represents a district at Boston, the curve
on the right principally represents the demand for power which takes
place between the hours of 8 A.M. and 3 P.M. A circular was addressed
to all the leading electric companies in America a short time ago,
asking if they supplied power as well as light, also for what purposes
it was used.
Answers were received from 56 companies, who stated that the motors
were employed for:—driving ventilator fans, collar-and-cuff machines,
printing-presses, various apparatus in repair-shops, sewing-machines,
coffee-mills, gun-shop tools, sausage-machines, elevators, lathes,
pumps, saws, ice-cream freezers, organ-bellows, and washing-machines.
The size of motors varied from one-eighth to 15 horse-power; 26
companies have supplied motors from arc light circuits, 14 from arc and
incandescent, and 16 from incandescent circuits alone. The motors are
principally owned by the subscribers, and are charged for at a rate
varying from £3 to £15 per horse-power per month. The motor business
is still in its infancy, but is cited to show how Electric Power can
supplant the steam-engine, especially for those purposes in which the
power required is small and complete control is desirable.
[Illustration: FIG. 15.]