Discoveries and Inventions of the Nineteenth Century

The few elementary facts which have been pointed out are absolutely necessary for the foundation of what is sometimes termed the theory of electricity, but which is properly no theory,—at least, not a theory in the same sense as gravitation is a theory explaining the motions of the planets, or even in the sense in which the hypothesis of the ether and its movements explains the phenomena of light. It is absolutely necessary to have a conception of some kind which may serve to connect in our minds the various phenomena of electricity, if it were only to enable us the more easily to talk about them. In default of any supposition which will shadow forth what actually occurs in these phenomena, we have recourse to what has been aptly termed a representative fiction: we picture to ourselves the actions as due to imaginary fluids—fluids which we know do not exist, but are as much creations of the mind as Macbeth’s air-drawn dagger; not, however, like his “false creation,” proceeding from “the heat-oppressed brain,” but intellectual fictions, consciously and designedly adopted for the purpose of enabling us the better to think of the facts, to readily co-ordinate them, and to express them in simple and convenient language. Non-scientific persons hearing this language usually mistake its purport, and imagine that the actual existence of an “electric fluid” is acknowledged. The accounts which appear in the newspapers of the damage done by thunderstorms are often amusing from the objectivity which the reporter attributes to the “electric fluid.” It is described, perhaps, as “entering the building,” “passing down the chimney,” then “proceeding across the floor,” “rushing down the gas-pipes,” “forcing its way through a crevice, and then streaming down the wall,” &c., in terms which imply the utmost confidence of belief in the existence of the “fluid.” With this intimation that the hypothesis of electric fluids is merely, then, a “façon de parler,” the reader will not be misled by the following brief explanation of the elementary facts in the language of the theory. In the natural state all bodies contain an indefinite quantity of an imponderable subtile matter, which may be called “neutral electric fluid.” This fluid is formed by a combination of two different kinds of particles, positive and negative, which are present in equal quantities in bodies not electrified; but when there is in any body an excess of one kind of particles, that body is charged accordingly with positive or negative electricity. Both fluids traverse with the greatest rapidity certain substances termed conductors; but they are retained amongst the molecules of insulating substances, which prevent their movement from point to point. When one body is rubbed against another, the neutral electric fluid is decomposed—the positive particles go to one body, the negative with which these positive 488particles were before united pass to the other body. The particles of the same name repel each other, but particles of opposite names attract each other; and it is this attraction which is overcome when the electricities are separated by friction or in any other manner. It will be observed that the above is nothing but the statement of the elementary facts in the language of the hypothesis. This system of the two fluids readily lends itself to the explanation of nearly all the phenomena presented in what is termed static electricity—that is, in those phenomena where the actions are conceivably due to a more or less permanent separation of the fluids. The grand discoveries in electricity turn, however, upon quite another condition, namely, one in which the two hypothetical fluids must be imagined as constantly combining, and here the utility of the hypothesis is less marked. Inasmuch, however, as there can be no doubt regarding the identity of the agent operating in the two sets of circumstances, the facts of dynamical electricity must still be expressed in the same language, with the aid of any additional conceptions which may give us more grasp of the subject.