he became the joint inventor of
the Edison-Sims torpedo, with Mr. W. Scott Sims, who sought his
co-operation. This is a dirigible submarine torpedo operated by
electricity. In the torpedo proper, which is suspended from a long
float so as to be submerged a few feet under water, are placed the small
electric motor for propulsion and steering, and the explosive charge.
The torpedo is controlled from the shore or ship through an electric
cable which it pays out as it goes along, and all operations of varying
the speed, reversing, and steering are performed at the will of the
distant operator by means of currents sent through the cable. During the
Spanish-American War of 1898 Edison suggested to the Navy Department the
adoption of a compound of calcium carbide and calcium phosphite, which
when placed in a shell and fired from a gun would explode as soon as it
struck water and ignite, producing a blaze that would continue several
minutes and make the ships of the enemy visible for four or five miles
at sea. Moreover, the blaze could not be extinguished.

Edison has always been deeply interested in "conservation," and much
of his work has been directed toward the economy of fuel in obtaining
electrical energy directly from the consumption of coal. Indeed, it
will be noted that the example of his handwriting shown in these volumes
deals with the importance of obtaining available energy direct from the
combustible without the enormous loss in the intervening stages that
makes our best modern methods of steam generation and utilization so
barbarously extravagant and wasteful. Several years ago, experimenting
in this field, Edison devised and operated some ingenious pyromagnetic
motors and generators, based, as the name implies, on the direct
application of heat to the machines. The motor is founded upon the
principle discovered by the famous Dr. William Gilbert--court physician
to Queen Elizabeth, and the Father of modern electricity--that the
magnetic properties of iron diminish with heat. At a light-red heat,
iron becomes non-magnetic, so that a strong magnet exerts no influence
over it. Edison employed this peculiar property by constructing a small
machine in which a pivoted bar is alternately heated and cooled. It
is thus attracted toward an adjacent electromagnet when cold and is
uninfluenced when hot, and as the result motion is produced.

The pyromagnetic generator is based on the same phenomenon; its aim
being of cours