Matter consists of atoms, which are hard, opaque, _unalterable_, of homogeneous substance, of the spheric shape, and naturally _inert_, therefore of inactive essence; being _inert_, various species of substance would be useless. The spherical shape admits immediate atomic contact, and leaves interstices uniformly throughout all bodies. There cannot be either communication or alteration of the essence of inert matter; and what the essence of unalterable matter may be, is impossible, and would be useless, to know. An element is any volume of atoms of the same size. There is no difference between elements but in the size of their atoms. Every element is a rarer medium to every other element of larger atoms; the minor is as a partial vacuum to the major, which involves the principle of _inequality_, on which motion depends. Correlative elements are any two, the atoms of one of which are fitted for the interstices of the other, and for no other interstices. Such elements will naturally be together. On the correlative principle magnetism depends. All bodies consist of several elements; there is nothing simple, but an element. Bodies are divisible, matter is not. All bodies include a portion of _elementary_ or _electric_ matter, which is removed without injury to their general texture. Matter can suffer no change but change of place. Weight is an accident of matter, the effect of motion: all _effect_ consists in motion; there is no result until effect has ended in rest. Rest being natural to inert matter, is no effect, has no cause. _There is no power but impulsive pressure_; nor is there any effect whatever attributable to _inertia_. The fundamental principle of _inertia_ is that only from which the philosophy of nature is deducible: all philosophy is false which is not consistent throughout with this universal, all-directing principle. * * * * * _Note._--The terms _electric_ and _elementary_ are of the same signification, which is, _highly rare_: quality and power to act are wholly out of the question with the inert atoms of the elements of bodies and matter. MOTION. Motion admits of no definition, from being but a local casuality of transitory endurance; motion is the same in all things, from an atom to a planet, against which all difference in velocity and direction makes no exception. Impulsive pressure is the only cause analogous to the mechanical effect motion; pressure is universal because matter is inert. Motion is not natural to _inert_ matter: the term is expressive of the local condition of a body, while the body is prevented remaining where it is, and while the body is being passed through contiguous portions of space. THERE IS NO CAUSE OF MOTION BUT PHYSICAL IMPULSE.