561. What is electricity?

Electricity is a property of force which resides in all matter, and which constantly seeks to establish an equilibrium.562. Why is it called electricity?

Because it first revealed itself to human observation through a substance called, in the Greek language, electrum. This substance is known to us as amber.563. In what way did electrum induce attention to this property of force in matter?

Thales, a Greek philosopher, observed that, by briskly rubbing electrum, it acquired the property of attracting light particles of matter, which moved towards the amber, and attached themselves to its surface, evidently under the influence of a force excited in the amber.564. What is amber?

It is a resinous substance, hard, bitter, tasteless, and glossy. It has been variously supposed to be a vegetable gum, a fossil, and an animal product. It is probably formed by a species of ant that inhabit pine forests. The bodies of ants are frequently found in its substance.

"He made darkness his secret place: his pavilion round about him were dark waters and thick clouds of the skies."

565. Why does the rubbing of a stick of sealing-wax cause it to attract small particles of matter?

Because it excites in the sealing wax that force which was first observed in the amber. Sealing-wax, therefore, is called an electric (amber-like) body.566. Why do we hear of the electric fluid?

Simply because the term fluid is the most convenient that can be found to express our ideas when speaking of the phenomena of electric force. But of the nature of electricity, except through its observed effects, nothing is known.567. What substances are electric?

All substances in nature, from the metals to the gases. But they differ very widely in their electrical qualities.568. What is positive electricity?

Electricity, when it exists, or is excited, in any body, to an amount which is in excess of the amount natural to that body, is called positive (called also vitreous).569. What is negative electricity?

Electricity, when it exists, or is excited, in any body, in an amount which is less than is the amount natural to that body, is called negative (called also resinous).570. Why is "positive" electricity called also "vitreous," and "negative" electricity called also "resinous"?

Because some philosophers believe that there is but one electricity, but that it is liable to variations of quantity or state, which they distinguish by positive and negative; while other philosophers believe that there are two electricities, which they name vitreous and resinous, because they may be induced respectively from vitreous and resinous substances, and they display forces of attraction and repulsion.571. Upon what do the electrical phenomena of nature depend?

Upon the tendency of electricity to find an equilibrium between its positive and negative states (assuming there to be but one fluid); or upon the tendency of vitreous electricity to seek out and combine with resinous electricity (assuming that there are two fluids).

"The Lord also thundered in the heavens, and the Highest gave his voice; hailstones and coals of fire."

572. How does the equilibrium of electricity become disturbed?

By changes in the condition of matter. As electricity resides in all substances, and is, perhaps, an essential ingredient in their condition, so every change in the state of matter—whether from heat to cold, or from cold to heat; from a state of rest to that of motion; from the solid to the liquid, or the Æriform condition, or vice versa; or whether substances combine chemically and produce new compounds—in every change the electrical equilibrium is disturbed; and, in proportion to the degree of disturbance, is the force exerted by electricity to resume its balance in the scale of nature.573. How does electricity seek to regain equilibrium?

By passing through substances that are favourable to its diffusion; therefore they are called conducting or non-conducting bodies, according as they favour or oppose the transmission of the electrical current.574. What substances are conductors of electricity?

Metals, charcoal, animal fluids, water, vegetable bodies, animal bodies, flame, smoke, vapour, &c.575. What substances are non-conductors?

Rust, oils, phosphorous, lime, chalk, caoutchouc, gutta percha, camphor, marble, porcelain, dry gases and air, feathers, hair, wool, silk, glass, transparent stones, vitrefactions, wax, amber, &c. These bodies are also called insulators. Some of these substances, as chalk, feathers, hair, wool, silk, &c., though non-conductors when dry, become conductors when wetted.

Insulating—preventing from escaping.576. Why are amber and wax classed among the non-conductors, when they have been pointed out as electrics, and used to illustrate electrical force?

It is because they are non-conductors that they have displayed, under excitement, the attractive force shown in respect to the particles of matter which were drawn towards their substances. If a bar of iron were excited, instead of a stick of wax, electricity would be equally developed; but the iron, being a good conductor, would pass the electricity to the hand of the operator as fast as it accumulated, and the equilibrium would be undisturbed.

"Yea, he sent out his arrows, and scattered them; and he shot out lightnings and discomfited them."—Psalm xviii.

577. What is the effect when electricity, in considerable force, seeks its equilibrium, but meets with insulating bodies?

The result is a violent action in which, intense heat and light are developed, and in the evolution of which the electric force becomes expended.578. What is the cause of electric sparks?

The electric force, passing through a conducting body to find its equilibrium, is checked in its course by an insulator, and emits a spark.579. What produces the electric light?

Currents of electricity pass towards each other along wires at the ends of which two charcoal points are placed. As long as the charcoal points remain in contact, the electric communication is complete, and no light is emitted, but, when they are drawn apart, intense heat and light are evolved.

580. What is the cause of lightning?

Lightning is the result of electrical discharges from the clouds.581. What develops electricity in the clouds?

Evaporations from the surface of the earth; changes of temperature in the atmospheric vapour; chemical action upon the earth's surface; and the friction of volumes of air of different densities against each other.

"His lightnings enlightened the world: the earth saw and trembled."—Psalm xcvii.

582. Why do these phenomena produce electricity?

Because they disturb the equilibrium of the electric force, and produce positive and negative states of electricity.583. When does lightning occur?

When clouds, charged with the opposite electricities approach, the forces rush to each other, and combine in a state of equilibrium.584. Why does lightning attend this movement of the forces of electricity?

Because the atmosphere, being unable to convey the great charges of electricity as they rush towards each other, acts as an insulator, and lightning is caused by the violence of the electricity in forcing its passage.585. Does lightning ever occur when the conducting power is equal to the force of the electricity?

No; electricity passes invisibly, noiselessly, and harmlessly, whenever it finds a sufficient source of conduction.