Miscellaneous Inventions - 5

Miscellaneous Inventions - 5

 Edison has never paid much attention to warfare, and has in general disdained to develop

inventions for the destruction of life and property. Some years ago, however, 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 course to

generate electrical energy directly from the heat of the combustible. The armature, or

moving part of the machine, consists in reality of eight separate armatures all constructed

of corrugated sheet iron covered with asbestos and wound with wire. These armatures are

held in place by two circular iron plates, through the centre of which runs a shaft,

carrying at its lower extremity a semicircular shield of fire-clay, which covers the ends of

four of the armatures. The heat, of whatever origin, is applied from below, and the shaft

being revolved, four of the armatures lose their magnetism constantly, while the other

four gain it, so to speak. As the moving part revolves, therefore, currents of electricity are

set up in the wires of the armatures and are collected by a commutator, as in an ordinary

dynamo, placed on the upper end of the central shaft.

A great variety of electrical instruments are included in Edison's inventions, many of

these in fundamental or earlier forms being devised for his systems of light and power, as

noted already. There are numerous others, and it might be said with truth that Edison is

hardly ever without some new device of this kind in hand, as he is by no means satisfied

with the present status of electrical measurements. He holds in general that the meters of

to-day, whether for heavy or for feeble currents, are too expensive, and that cheaper

instruments are a necessity of the times. These remarks apply more particularly to what

may be termed, in general, circuit meters. In other classes Edison has devised an

excellent form of magnetic bridge, being an ingenious application of the principles of the

familiar Wheatstone bridge, used so extensively for measuring the electrical resistance of

wires; the testing of iron for magnetic qualities being determined by it in the same way.

Another special instrument is a "dead beat" galvanometer which differs from the ordinary

form of galvanometer in having no coils or magnetic needle. It depends for its action

upon the heating effect of the current, which causes a fine platinum-iridium wire enclosed

in a glass tube to expand; thus allowing a coiled spring to act on a pivoted shaft carrying

a tiny mirror. The mirror as it moves throws a beam of light upon a scale and the

indications are read by the spot of light. Most novel of all the apparatus of this measuring

kind is the odoroscope, which is like the tasimeter described in an earlier chapter, except

that a strip of gelatine takes the place of hard rubber, as the sensitive member. Besides

being affected by heat, this device is exceedingly sensitive to moisture. A few drops of

water or perfume thrown on the floor of a room are sufficient to give a very decided

indication on the galvanometer in circuit with the instrument. Barometers, hygrometers,

and similar instruments of great delicacy can be constructed on the principle of the

odoroscope; and it may also be used in determining the character or pressure of gases and

vapors in which it has been placed.