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the radii be enlarged, and this will tend to expand and protrude the atmospherules, hence, if liberty be allowed, ethereal matter will escape through the sides of the vessel, till the given intensity is attained, and hence an equilibrium is produced, and the given pressure will be supported at that intensity. The converse is manifest.

Cor. 1. If the radii be diminished beyond certain limits the gas will become a liquid or solid, since the tenacious atoms will thus be capable of passing through the atmospherules.

Cor. 2. If the force of the tenacious atoms be given, the whole quantity of ethereal matter, requisite to support a given pressure, at a given intensity, is less when the radii are greater, and the converse.

Cor. 3. Hence, in general, the quantity of ethereal matter requisite to support a given pressure at a given intensity, will be as some function of the forces directly, and radii of the spherules inversely.

Cor. 4. Under the assigned limits of pressure, equal volumes of simple gases of different kinds, under the same pressure and at the same temperature, will contain an equal number of atoms.

Cor. 5. If a collection of atoms, at a given intensity and pressure, constitute a gas; the same collection at that pressure and intensity, might constitute a liquid, or solid, merely by increasing the force of the atoms or diminishing the radii sufficiently, or by both of these al

terations.

Cor. 6. If there be two simple bodies, the one a gas, and the other, either a liquid or solid, at a given intensity and pressure; then, the atoms of the latter have either a greater force or a less spherule, or they differ in respect of both these.

PROP. 24. If a collection of atoms, constituting a gas,

be contained in a vessel at a given intensity; then the density will vary as the compressing force, provided that the pressure is within such limits, that the whole shall continue in a gascous form; and that time is allowed for acquiring the given intensity, after the action of the compressing force.

Let the force be applied in very small portions at successive intervals, and such in quantity, that at each application, the density shall be equally increased, now after the first small increase of pressure the gas will act with increased force on the sides of the vessel, and consequently ethereal matter will escape till the intensity of the gas is reduced to the given intensity of the sides of the vessel; hence the resistance to the second application of the compressing force will be equal to that of the first, and therefore these two first small portions of compressing force will be equal; in the same manner it may be shewn that the third is equal to the second, and consequently to the first, and so of the rest; that is equal increments of density are produced by equal increments of compressing force.

Cor. 1. It is evident that if the pressure be such, that a portion of the gas is converted into a liquid, or solid, the above cannot hold, a portion of the gas being removed.

Cor. 2. The law of repulsion of the atoms does not determine the law of condensation, because the actions are modified by the escape of ethereal matter.

PROP. 25. When a gaseous body is constituted of atoms, whose forces at the surfaces of the spherules are equal, or nearly equal; they will be less disposed to combine, and form a new body, than when the forces differ considerably at those situations.

For the forces at the surfaces being equal, the ethereal atoms, forming the atmospherules, will have the same density at those surfaces, and will therefore be affected much alike by varations in pressure and the addition or abstraction of ethereal matter, and hence the atmospherules will not readily pass the one to the other, but will maintain themselves in a separate state on their own atoms, more firmly than when the forces are much greater on one surface than on the other, the circumstances being alike in other respects.

Cor. 1. When the spherules are also equal, the tendency to combine, for similar reasons, will be less than when they are unequal.

Cor. 2. Bodies constituted of particles, of which the forces of their atoms at the surfaces of their spherules are nearly equal, will in general be less stable and perma nent than others whose spherules are of unequal magnitude.

PROP. 26. The actions of bodies upon atoms or particles affect their atmospherules, causing them to move towards, or from the body, according to circumstances; and thus rendering them more or less susceptible of union with other substances.

Let AB (fig. 43.) represent the upper surface of a body acting on the particle Dm, at the side m, then it is manifest, that, if ethereal matter will readily apply itself to, and be diffused on AB, the atmospherule of Dm will be brought chiefly towards AB, especially if the force of D be small; hence the atom n will more easily combine with D. On the contrary if AB have much ethereal matter already attached to it, so as to form on its particles extended atmospherules, it will resist the ethereal matter of Dm at m, and hence will cause the atmospherule of Dm

to extend more towards n, and hence will oppose the combination of n with D, by pressing on the parts at which they are nearest to each other.

PROP. 27. If a globular solid body A, (fig. 48.) be immersed or contained in a gaseous fluid, and both the body and the gas imbued with ethereal matter, so as to be in a state of equilibrium, the ethereal matter of the gas extending around its atoms equally on every side; and if now a considerable quantity of ethereal matter be communicated, by some means, to the solid body, and diffused over its parts, the atmospherules of the atoms of the contiguous gas will be extended outward from the surface of the globe.

For the ethereal matter communicated to the solid A, will be most of all abundantly diffused at its surface, towards which it will tend (prop. 17. and its cor.) hence evidently it will press on the atmospherules of the adjacent atoms of the gaseous substance on the side which is towards the solid A, and will therefore make them extend outward, as at n and m, &c. and the action of these protruded atmospherules will produce a similar effect on the next more distant ones, as at P, and q, &c. and hence the several atmospherules will be extended outward with diminishing effect, to a considerable distance from the solid A on all its sides, as shewn by the short lines on the little circles, which are intended to denote the spherules of the atoms of gas, the short lines shewing the direction in which the atmospherules are extended.

PROP. 28. The same things being supposed, as in the last proposition, except that the ethereal matter is, by some means now taken away from the solid, instead of being added to it; the atmospherules of the atoms of the contiguous gas, in this case will be extended towards the solid body A, as in fig. 49, on all its sides.

This is equally evident as the former, for the pressure of the ethereal matter, being removed in part, and chiefly (prop. 17. and cor.) from the surface of the solid A, that of the adjacent atoms of the gas as at m and n, &c. will extend towards A, and this diminishing the ethereal fluid on the further side of those atoms will produce a similar effect on the next stratum of the gas, as at p, and q, &c. decreasing gradually as the distance from A inThe short lines drawn toward the solid in the figure, are to shew the sides on which the atmospherules of the gas are extended.

creases.

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