cally. These observations, though inclining to conjecture, are sufficient to shew, that though a mass of matter is very much altered in its dimensions, its continuity may still be uninterrupted.

There is another way of considering matter, so as to account for its extension, without supposing it to lose its continuity. The down of a thistle is composed of a central particle, which is the seed, furnished with elastic radii; while these lie, in what we may call their fixed state, within the calyx of the mother plant, a vast number of them is comprehended in a very small compass: but when they are relaxed or rarefied, as in their volatile state, a bushel might be filled with what lay in a few cubic inches. The force with which a medium, consisting of such parts, would resist compression, would be more or less according to the elasticity of the radii attached to the central particles; and if we suppose all the radii disjoined and independent of their centres, the condition of the medium will be very different.

Gravity not essential to Mutter,

1

Another very considerable property of

matter

matter is gravity or weight; which, though very extensive, is rather an accident to matter than essential to its nature.

For cer

tainly all matter has not weight. Bodies differing in kind do not preserve a constant relation to each other in respect of weight, when they are in different forms, and differently acted upon. It is the nature of iron to sink in water with a superior specific gravity; but the atoms of iron will be suspended in water. Sulphur will sink in oil; but if the oil be heated to a proper degree, (with which heating it is rarefied, and becomes specifically lighter,) the atoms of sulphur will ascend and be suspended in it for ever, so as to constitute a medicine of eminent service both for internal use and external application. The same is observable in other bodies: whence it is found, that relative weight is a variable thing, and that atoms in a state of separation are not affected by it, as when they are formed into masses, and compose bodies.

Were gravity essential to matter, all matter would constantly tend (or at least preserve a tendency) towards its proper centre. The matter near the earth would all tend toward the earth, and resist every other direction.

rection. The matter near the sun would all tend towards his orb. But this is by no means agreeable to nature. Here upon earth the electric fluid, a sort of matter which seems to fill the world, and is of such consequence that it seems to be the life and soul which invigorates all the rest, will move in every direction indifferently; and fire, when agitated, is rather disposed to ascend in a direction contrary to that of heavy bodies. In the regions near the sun, the matter of his light is flying off, that is, ascending from his orb incessantly, to replenish the world and act upon the planets. Therefore matter,

considered in itself, is indifferent to every direction; which indeed is very clearly implied in what all modern philosophers have allowed, that it is indifferent to motion; because all motion must be in some direction, and we are obliged to suppose motion, before we can suppose direction. If matter, as such, has no motion of its own, it has no direction. If it is found in fact to incline to one direction rather than another, on account of what we call its weight, this happens to it from the established constitution of the world, and the operation of external causes; not from any quality inherent in the

matter

matter itself. Though fire, in its natural state, has no weight, it may be so attached by the operations of chemistry to the parts of solid matter, as to partake of their property, and increase the weight of the whole mass considerably by gravitating together with it. Some modern chemists have supposed, that matter deprived of its inflammable principle is absolutely heavier than before; which is only to express the same thing another way for they suppose, that the inflammable principle naturally resident in it, made it absolutely lighter before the operation of calcination; we suppose that the fixity of fire makes it absolutely heavier after the operation in either case, its absolute gravity is a mutable thing, and therefore not essential to the matter.

Polarity of Atoms.

A very ingenious modern chemist, who has earried the experiments of chemistry to a great height*, ascribes to the primary constituent parts, or atoms of solid bodies, a certain physical direction, which he calls polarity, as being analogous to that property

* Dr. Higgins.

of

of the magnetic needle, which occasions it to take a polar direction. It is not meant that the atoms of bodies are turned north or south by the influence of the elements upon 'them; but that when the loose parts of bodies are brought together into a concrete mass, those parts, if undisturbed during their settlement, take an orderly arrangement, which is the consequence of an uniform direction in them all.

On this principle crystals are formed out of fluids; and hence it is that homogeneous masses have the same specific densities throughout their whole substance. If nature is interrupted during the specific arrangement of the parts, the concrete will not be perfectly formed, but will fail in some of its properties. So nice and critical an operation is the arrangement of the parts which form sonorous bodies, that even the barking of a dog, as I have been informed, will hurt the tone of a bell, if it happens while the cast metal is settling in the mould.

When bodies are increased by a very slow accession of parts, which is generally the case in all the stated operations of nature, the parts, as they fix themselves, have time to assume that orderly direction which is necessary