PHYSICS.
In the science of material things, mechanics takes account of forces that act on masses from without; physics, of those that act from within, or which, in some way, modify the condition of the bodies themselves. Both branches were, till recently, included in the vaguely comprehensive term “Natural Philosophy,” and the partial separation observed in modern treatises and text-books gives a little more distinctness to the facts presented. Under the former the earth is contemplated as a planet, obedient to the universal law of gravitation, and moving regularly in its orbit. The mechanism of the system is complete; the measure and adjustment of all the parts perfect.