nd
an electric lamp be connected from one to the other wire, the lamp
will be lighted--will grow white hot,--hence _incandescent light_.
The instant this lamp is turned on, the revolving spool feels a
stress, the magnets by which it is surrounded begin to pull back on
it. The power of the water wheel, however, overcomes this pull. If one
hundred lights be turned on, the backward pull of the magnets
surrounding the spool will be one hundred times as strong as for one
light. For every ounce of electrical energy used in light or heat or
power, the dynamo will require a like ounce of mechanical power from
the water wheel which drives it.

The story is told of a canny Scotch engineer, who, in the first days
of dynamos, not so very long ago, scoffed at the suggestion that such
a spool, spinning in free air, in well lubricated bearings, could
bring his big Corliss steam engine to a stop. Yet he saw it done
simply by belting this "spool," a dynamo, to his engine and asking the
dynamo for more power in terms of light than his steam could deliver
in terms of mechanical power to overcome the pull of the magnets.

Electricity must be consumed the instant it is generated (except in
rare instances where small amounts are accumulated in storage
batteries by a chemical process). The pressure of a button, or the
throw of a switch causes the dynamo instantly to respond with just
enough energy to do the work asked of it, always in proportion to the
amount required. Having this in mind, it is rather curious to think of
electricity as being an article of export, an item in international
trade. Yet in 1913 hydro-electric companies in Canada "exported" by
means of wires, to this country over 772,000,000 kilowatt-hours (over
one billion horsepower hours) of electricity for use in factories near
the boundary line.

This 250 cubic feet of water per minute then, which the farmer has
measured by means of his notched board, will transform by means of its
falling weight mechanical power into a like amount of electrical
power--less friction losses, which may amount to as much as 60% in
very small machines, and 15% in larger plants. That is, the brook
which has been draining your pastures for uncounted ages contains the
potential power of 3 and 4 young horses--with this difference: that it
works 24 hours a day, runs on forever, and requires no oats or hay.
And the cost of such an electric plant, which is ample for the needs
of the average farm, _i