Properties of Matter. The atoms of all matter in general have the following properties: 1. Hardness. Impenetrability. 3. Resistance. 4. Mobility. 2. When we speak of hardness as one of the properties of all atoms, we do not mean it in such a sense as when we compare one body with another, and say, this is hard in respect of that; but hardness absolute, such as cannot be altered or wrought upon by any violence from collision, attrition, or any other external force. Impenetrability is a necessary consequence of the former property. By this it is meant, that two units of matter cannot exist at the same time in the same place; so long as the one retains its place, it must necessarily exclude the other. Bodies, however, may be understood to penetrate one another's dimensions so far as to be circumscribed by the same space; or, the same space may be understood to comprehend at the same time the parts of very different bodies. When copper and tin are melted together, the bulk of the copper is so little increased by the admixture of the tin, that the parts of the latter must haye F 3 have found room to seat themselves within the pores of the former; and it is probably owing to this filling up of the pores, that the sound of the mass is so much improved, though the brittleness may have some share in the effect. If a vessel were to be filled with musquet balls, many interstitial spaces would be left, which might be filled with sand; and this also would leave its vacuities, which might be supplied with water: the water in like manner contains the particles of air; and air again contains the particles of a finer ether, which is every where expanded. On this principle the visible world is filled with matter for if grosser bodies are excluded from any space, more subtile ones, which no art can exclude, will be present in it. It cannot be proved, or reasonably supposed, that there is any point of space within the limits of the solar system capable of admitting a particle of light, be it either within the pores of solid bodies, or in the free spaces of the heavens, but what hath at all times such a particle in it. How this is to be understood, and how it consists with the free motion of bodies, will be shewn hereafter, when we come to consider the nature and causes of motion. When When we allow a principle of resistance to atoms, we do not mean it in such a sense as if they were made only to be inert, and stand in the way for, by the constitution of the world, some are so far from resisting motion, that in fact they are already in motion, and are instrumental to the motion of others: but we mean only, that as they have no innate powers of motion in themselves, they must, in consequence of their impenetrability, resist any force that is applied to displace them. If we consider the fact of resistance as it now stands, it seems rather to take place from that certain determination which all the parts of matter are under, and in consequence of which they require a force to turn them out of that way which is appointed to them by the established laws of nature. How far any parcel of matter would resist, if it could be taken independent of the present frame of nature, and what force would be requisite in such a case to move any given quantity of matter in all directions indifferently, we cannot say, because we cannot place any matter in such a state to make the trial. As things now are, the actual resistance we find in matter being, cæteris paribus, in proportion to its weight, it seems to be the necessary consequence of that effect which we call gravity: so that if any matter can be placed under such circumstances, as to be less affected by gravity, (which is the case with bodies floating in a liquor of the same specific gravity with themselves,) their resistance will be lessened; and if there he any subtile fluid not subject to the effect of gravity, such a fluid will have no sensible resistance at all. Mobility in atoms is nothing more than a capacity of being moved by any external mechanical force applied to them; not that they are endued with any internal power of moving themselves. If we should say, that matter is by nature inert, and resisting, and indifferent to motion, and then should proceed to give the same matter a disposition to move without some external force, we should invest it at once with power and impotence, with sluggishness and activity, which cannot both be predicated of it without contradiction. The trumpet hath a capacity of sounding, but never till it is sounded: of itself it is dead and silent, and, as long as left to itself, must always remain so. Matter, in like manner, hath a capacity of motion, not an ability to move; neither doth any matter Let us act but so far as it is acted upon. imagine the present laws of nature suspended, and all matter annihilated, except one single atom; we all confess that this atom can have no inclination to move one way rather than another, but must remain absolutely at rest; and all this from its own inert nature. If we introduce another atom at a distance from the former, they will both be at rest; for the properties of matter are not changed by having two atoms instead of one. Lay two trumpets near each other, and you will have no more sound than from one, till you apply some force which is not natural to either. To invest matter with any innate powers or self-inclinations to motion, call them by what names you please, is as contrary to the real nature of matter, as to suppose that all trumpets are born with lips and lungs, and breath of their own. A stringed instrument has the capacity of sending forth all possible harmony; but it must first be acted upon, either by the vibratory motion of the air (as in the Eolian harp), or by the hand of the master immediately, or by the interposition of a series of machinery. Such, then, is the mobility of matter; it is a capacity of being moved and acted upon, but no |