have been introduced. Inertia, so far as I am aware, has always been accepted as an inscrutable fact, or ignored.
An entity with four unexplained properties is regarded as still a long way from satisfactory simplicity. But a more important consideration is that the entity is always found associated with its fellow or fellows in a dependent and artificial way (when identified at all), which indicates an advance from primitive independence and simplicity. The complexity of the simplest atom we know of has already been referred to. The resemblance of the atoms to manufactured articles was pointed out by Sir John Herschel; and not only that, but they resemble articles made in quantities by machinery, all exactly alike, like Waltham watches or Springfield guns. And the fact that any recognizable atom, like that of hydrogen, for instance, is always exactly the same thing, whether derived from the ocean or the coal measures, or from the occluded gas of a meteorite, or inspected in the sun and stars, as pointed out by Maxwell ("Encyclopædia Britannica," ninth edition, article "Atom"), would seem to indicate that it must be the result of an undeviating process, and in its ultimate derivation made up of finally discrete entities, and not out of continuous substance, whatever that may mean. The fact, too, of its occurrence at such wide points of distribution, indicates the unity of the present scheme of evolution, as well as the great antiquity of its origin, and its persistency of type.
We have at present no clew to the evolutionary history of the atom. The atom I distinguish both from the ultimate particle without parts, and from the complex derivative molecule of the chemical elements, such as all those we know of are. In fact, these must also be distinguished from the still differently organized compound molecule of the chemical combinations, which can be taken apart, and the enormously complicated system of the organic molecule, as of oil or albumen, which, if a body so simple as iron contains more than seven hundred couples, must contain rotary elements which can only be numbered by millions.
The atom, or elementary couple, is conceived as having dimension, figure, and polarity, and also perfect elasticity, by reason of its harmonic vibration. We have to seek an origin for it if we are at all impressed with its artificial and evolved character. Its artificiality lies in its rotary motion; such motion being due to and maintainable only by a composition of forces.
The weight and ponderosity of matter have proved a stumbling block to the conceptions of the later philosophers—especially after Newton had generalized them as attraction and inertia—far more than the equally unexplainable property of resistance, though why, it is difficult to say. Lucretius found no such difficulty with the conception of weight, for his corpuscles all naturally tended "downward," so uncosmical were his ideas. Le Sage revived and modified the hy-
