Dr. J. Hopkinson has not only improved upon the Edison
dynamo, and obtained 94 per cent. of the power applied in the form of
electrical energy, but he got 50 horse power out of the same quantity of
iron and copper where Edison could only get 20 horsepower--and, though
the efficiency of this generator is perfect, it could not be called an
efficient motor, suitable for locomotion by land or water, because it
is still too heavy. An efficient motor for locomotion purposes must not
only give out in mechanical work as nearly as possible as much as the
electrical energy put in, but it must be of small weight, because it has
to propel itself along with the vehicle, and every pound weight of
the motor represents so many foot pounds of energy used in its own
propulsion; thus, if a motor weighed 660 pounds, and were traveling at
the rate of 50 feet per minute, against gravitation, it would expend
33,000 foot pounds per minute in moving itself, and although this
machine may give 2 horse power, with an efficiency of 90 per cent.
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