discernible massules of bodies have any particular figure, it is natural to suppose that the indiscernible ones, out of which they are more intimately composed, may have the same, or a similar figure; and that the figure of the whole arises from the figure of the parts.

Many of the effects of bodies may be naturally derived from the configuration of their particles: as for example, the spiculated are sharp and corrosive, piercing and wounding the parts to which they are applied, while the globular are insipid and balsamic. Hence the spicular poisons, as antimony and sublimate, may be rendered inoffensive by sheathing their points in oil or wax. The powdered glass of antimony, by being cerated, that is, mixed with a proper quantity of melted beeswax, becomes a gentle and healing medicine; though a single grain of the same powder, in its naked state, would vomit a strong man to death. Sulphur, which when cold is a brittle oil, has the same effect in sheathing the parts and checking the effects of corrosive medicines, such as the preparations of mercury and antimony. The solidity and fluidity of different bodies may depend in some measure on the figure of their particles,

the

the globular composing fluids, which admit of a free motion among themselves, while the angular settle into solid bodies, whose parts are immoveable. But solidity and fluidity is also certainly owing to other causes, because the same mass will be fluid or solid under different circumstances. Water fixes into solid ice under a certain degree of cold; and gold or iron, with certain degrees of heat, may be made to flow like oil or water: whence it may be collected, that these different conditions depend rather on the state of that elementary matter which flows round about them, and is within their pores.

Divisibility of Matter.

The parts of matter may be divided from each other, without any limits which we are able to determine: we may therefore allow, that matter is indefinitely divisible; but if we should affirm it to be infinitely divisible, we shall have some monstrous absurdities to encounter. Suppose there are two masses of matter, A and B, and that B is equal to twice A; if the parts of both these masses are infinite in number, then one of these two consequences must follow, either that the

VOL. IX.

less

less is equal to the greater, and so a part equal to the whole; or that we shall have two infinites, one of which is but a part of the other, which is contrary to all the ideas we have of infinity. So again, if the whole is finite, while the parts are infinite, it must follow, that the parts are greater than the whole; or, which comes to the same, that parts infinite in number will compose an whole that is finite. It is impossible to imagine the parts of matter so far divided but that number may be applied to measure them, because we can increase numbers in our imagination as fast and as far as we can divide the parts of matter; but hence it will follow, that the parts cannot be infinite, because this will infer the necessity of an infinite number, which is an absurdity, because it is a number to which you cannot add one.

Mathematicians are wont to illustrate their thoughts by lines, and their properties; and they sometimes give the name of demonstrations to their arguments, when they are nothing more than illustrations or diagrams, which express the mind of the illustrator, but prove nothing. According to the different lights in which a subject is considered, the application of different lines will lead to contrary

2

trary conclusions. It would be easy enough to shew, on such principles, that a given quantity of matter is both finite and infinite; that it may be divided without end, and that there must necessarily be an end of the division. Therefore, it is safer on many occasions to be guided by reason, and the nature of things, at least in matters of argumentation, than by diagrams, which are applicable to contradictions, and may, indeed, be accommodated to any thing. It is also very dangerous to follow the conceptions of the imagination, which are often very deceitful, and lead us away from more rational parts of science, to wander about in barren regions, where there is no certain improvement. The imagination may suppose a series of musical sounds, in octaves, one above another, without end, and a stretched musical string upon a monochord may seem capable of perpetual bisection; but in fact, the ear is bewildered when sounds are continued but a few octaves above or below the middle pitch () of the musical scale. Such speculations are of no use; and, when minutely pursued, serve only to deceive and perplex the understanding.

How far soever matter may be divisible in its own nature, we can conceive no idea of

its composition, but as it consists of units. All substance is measured either by number or weight: number is made up of units, and weight is no practical measure, till some elements are fixed upon as the units of which all other weights are composed. We therefore find ourselves under the necessity of considering all matter as made up of atoms or units; and it is most reasonable to sup pose, that all bodies, which are the same in kind, agree in the configuration of their smallest parts, and consist of elements rendered permanent and unchangeable by the express design of the Creator; otherwise, the world that now is might differ widely from that which was made in the beginning: the original properties of bodies would be lost, and new ones might arise without end, and without utility. "That nature (saith Sir "Isaac Newton) may be lasting, the changes "of corporeal things are to be placed only "in the various separations and associations, " and motions of those permanent particles; "compound bodies being apt to break, not "in the midst of solid particles, but where "those particles are laid together, and only "touch in a few points*."

*Newt. Opt. Q.31.

Properties