Man, like every other natural substance, is a compound of force and matter. "Respiration," says Liebig, "is the falling weight, the bent spring, which keeps the clock in motion; the inspirations and respirations are the strokes of the pendulum which regulates." Atoms of matter, through the instrumentality of living force, cohere and coalesce under endless complex conditions into endless varieties of form and substance; so also the activities of man, corporeal and intellectual, result in vast accumulations of experiences, which accumulations become the property of the whole society. Society, like matter, is composed of units, each possessing certain forces, attractive and repulsive; societies act upon each other, like celestial bodies, in proportion to their volume and proximity, and the power of the unit increases with the increase of the mass. In association there is a force as silent and as subtle as that which governs atoms and holds worlds in equipoise; its grosser forms are known as government, worship, fashion, and the like; its finer essence is more delicate than thought. It is this social force, attractive and repulsive, that binds men together, tears them asunder, kneads, and knits, and shapes, and evolves; it is the origin of every birth, the ultimate of every activity. Mechanical forces are manifest in machines, as the lever, the wheel, the inclined plane; professional force is manifest in intellectual ingenuity, literature, art, science, which are the machines of human progress. [Sidenote: MATERIALITY ACTING ON THE MIND.]