tors, for heating the cables laid along the bottom of our
canals to prevent their freezing in winter, and for almost every
conceivable purpose. Sometimes a man has a windmill on his roof for
light and heat; then, the harder the wintry blasts may blow the
brighter and warmer becomes the house, the current passing through a
storage battery to make it more steady. The operation of our ordinary
electric railways is very simple: the current is taken from an
overhead, side, or underneath wire, directly through the air, without
the intervention of a trolley, and the fast cars, for they are no
longer run in trains, make five miles a minute. The entire weight of
each car being used for its own traction, it can ascend very steep
grades, and can attain high speed or stop very quickly.

"Another form is the magnetic railway, on which the cars are
wedge-shaped at both ends, and moved by huge magnets weighing four
thousand tons each, placed fifty miles apart. On passing a magnet, the
nature of the electricity charging a car is automatically changed from
positive to negative, or vice versa, to that of the magnet just passed,
so that it repels while the next attracts. The successive magnets are
charged oppositely, the sections being divided halfway between by
insulators, the nature of the electricity in each section being
governed by the charge in the magnet. To prevent one kind of
electricity from uniting with and neutralizing that in the next section
by passing through the car at the moment of transit, there is a "dead
stretch" of fifty yards with rails not charged at all between the
sections. This change in the nature of the electricity is repeated
automatically every fifty miles, and obviates the necessity of
revolving machinery, the rails aiding communication.

"Magnetism being practically as instantaneous as gravitation, the only
limitations to speed are the electrical pressure at the magnets, the
resistance of the air, and the danger of the wheels bursting from
centrifugal force. The first can seemingly be increased without limit;
the atmospheric resistance is about to be reduced by running the cars
hermetically sealed through a partial vacuum in a steel and toughened
glass tube; while the third has been removed indefinitely by the use of
galvanized aluminum, which bears about the same relation to ordinary
aluminum that steel does to iron, and which has twice the tensile
strength and but one third the weight of steel.