Page:Popular Science Monthly Volume 78.djvu/577

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An ion is a charged atom, an atom carrying a quantity of electricity, such, for instance, the dissociated atoms of an electrolyte. Ions can be compared to diminutive Leyden jars, and as it has been discovered that they all carry the same charge and that each atom has the same electrical capacity, the physicist has been enabled to count the actual number of ions in any gas by the electrical properties of the gas. If an ion is electro-positive, it is known as a cation; if electro-negative, as an anion—two old words due to Faraday, which are immediately related to the familiar terms of cathode and anode.

Whatever the essential difference between them may be, the two electrical states (+ and &minus;) may be said to differ chirally only, or, to give a more distinct if rather crude mechanical analogy, one may imagine that two discs, each suspended by a thread in its center, are revolving at a high uniform speed; if they revolve in the same direction they will spring apart as soon as they come into contact, part of their motion of rotation being converted into motion of translation; if they revolve in opposite directions their motions will not interfere, in other words they will be "in mesh." Thus, according to this conception, each is the enantiomorph, or opposite form, of the other; positive and negative charges of ions are equal but opposite. This idea of opposite charges owing their difference to opposite directions of rotation is only a working hypothesis, but is worth keeping in mind.

Having adopted negative and positive ions as the basis of matter, we must now examine the distinction between force and energy before going any further into the sub-atomic world. Force is the action, the manifestation of energy, just as visibility is a physiological manifestation of light. Light, in the abstract, is energy; in the concrete, as something that we see, it is a force. It is propagated as energy and manifested as a force; force, therefore, always implies matter.

As we shall have opportunities to see later, all energies are almost certainly modes of motion. Matter, on the other hand, is perhaps best described as whatever can occupy space, but this description is not suited to all theories. If motion is an essential property of matter, matter might be best described as whatever possesses energy in virtue of its motion; but in this essay the nature of matter will be discussed, and not its structure.

The ether, in which energy is manifested, may be said to have owed its recognition to the impossibility of believing in action at a distance and through a void space. Sir William Crookes at one time suggested a fourth state of matter for the ether; before accepting this theory, however appropriate it may appear, it seems reasonable that all the