nish this distance; nor does any force which can be applied bring them into actual mathematical contact; a force may indeed be applied sufficient to break the glasses into pieces, but it may be demonstrated that it does not diminish their distance much beyond the Too part of an inch. There is, therefore, a repulsive force, which prevents the two glasses from touching each other.

There exists, therefore, a repulsion between bodies; this repulsion takes place while they are yet at a distance from each other; and it opposes their approach towards each other.

The cause, or the nature, of this force is equally inscrutable with that of attraction, but its existence is undoubted; it increases, so far as has been ascertained, inversely as the square of the distance, consequently at the point of contact it is infinite.

The following experiments will serve to prove the energy of repulsion more fully.

EXPERIMENT I.

We have seen (Experiment III. p. 56) that when a glass tube is immersed in water, the fluid is attracted by the glass and drawn up into the tube; but if we substitute mercury instead of water we shall find a different effect. If a glass tube of a large bore be immersed in this fluid it does not rise, but the surface of the mercury is considerably below the level of that which surrounds it.

In this case, therefore, a repulsion takes place between the glass and the mercury, which is even considerably greater than the attraction existing between the particles of the mercury, and hence the latter cannot rise in the tube, but is repelled, and becomes depressed.

EXPERIMENT II.

When we present the north pole of a magnet, A, to the same pole of another magnet, B, suspended on a pivot, and at liberty to move, the magnet B will recede as the other approaches; and by following it with A, at a proper distance, it may be made to turn round on its pivot with considerable velocity.

In this case there is evidently some agency which opposes the approach of the north poles of A and B, which

acts as an antagonist, and causes the moveable magnet to retire before the other. There is, therefore, a repulsion between the two magnets, a repulsion which increases with the power of the magnets; which may be made so great, that all the force of a strong man is insufficient to make the two north poles touch each other. The same repulsion is equally obvious in electrical bodies; for instance,

EXPERIMENT III.

If two small cork balls be suspended from a body with silk threads so as to touch one another, and if we charge the body in the usual manner with electricity, the two cork balls separate from each other, and stand at a distance proportional to the quantity of electricity with which the body is charged; the balls, of course, repel each other.

EXPERIMENT IV.

If we rub over the surface of a sheet of paper the fine dust of lycopodium or puff-ball, and then let water fall on it in small quantities, the water will instantly be repelled, and form itself into distinct drops which do not touch the lycopodium, but roll over it with uncommon rapidity. That the drops do not touch the lycopodium, but are actually kept at a distance above it, is obvious from the copious reflection of white light.

EXPERIMENT V.

If the surface of water contained in a basin be covered over with lycopodium, a solid substance deposited at the bottom of the fluid may be taken out of it with the hand without wetting it. In this case the repulsion is so powerful as to defend the hand completely from the contact of the fluid.

INFERENCES.

The various substances which compose the globe are therefore subject on the one hand to a general law which tends to unite them together, and on the other hand to another agent which tends to disunite, or to remove them to a greater distance. Hence it is impossible to produce

any change whatever in bodies without interrupting these respective agencies.

The great business of the chemist is to examine the changes arising from these agencies, and to trace the laws by which they are regulated. In doing this he investigates the operations of nature, and endeavours to point out their dependencies on one another. For that purpose he places different bodies in contact with each other under a diversity of circumstances, and observes the phenomena which accompany their action. He endeavours to trace the conditions under which they are produced, and examines the properties of the new compounds; thus making them subservient to the improvement of the arts, and rendering them the ministers of our necessities, comforts, and enjoyments. (See Appendix No. 5.)

CORPUSCULAR ATTRACTION.

OR,

ATTRACTION OF AGGREGATION.

PART VIII.

CORPUSCULAR attraction, or attraction of cohcsion or aggregation, is that power by means of which the similar particles of bodies attract each other and become united into one mass, without changing, in the least, the chemical properties they possessed before their union. The bodies may be in a solid, fluid, or aeriform state.

Corpuscular attraction is different in different bodies. It is always in an inverse ratio to the power of repulsion, or the quantity of caloric interposed between the particles of the acting bodies.

It becomes obvious from this, that the agency of corpuscular attraction consists in a mere successive and con-stant accumulation of similar particles into one mass; and that it produces adherence of surface, or apparent contact in the ratio of the surfaces.

This force is inherent in all the particles of all bodies (caloric and light perhaps excepted) we never find the particles of bodies in a detached state, but constantly in masses of greater or smaller magnitude, made up of an indefinite number of particles united together by virtue of the force of cohesion.

SECT. I.

INSTANCES OF CORPUSCULAR
ATTRACTION.

THE simplest case of the exertion of corpuscular attraction is that where two bodies, placed in mutual contact with each other, form a direct union, without changing their chemical properties.

EXPERIMENT I.

If different particles of sulphur be melted together, they form an uniform mass or whole, the particles of which are held together by virtue of the power of corpuscular attraction, but the properties of the body are not altered.

The same effect takes place when pieces of the same metal, or particles of resin, wax, &c. are united in a similar manner.

Innumerable other instances might be advanced, were not the subject obvious to every one.

MEASUREMENT OF CORPUSCULAR
ATTRACTION.

The force of corpuscular attraction in solid bodies may be measured by the force or weight necessary to demolish it. Thus, if a rod of metal, glass, wood, &c. be suspended in a perpendicular direction, and weights, be attached to its lower extremity, till the rod is broken by them, the weight attached to the rod just before it broke is the measure of the cohesive force of the rod.

It is also expressed by comparing it with other bodies: thus it is said that a ruby is softer than a diamond, but harder than the hardest steel, because with it the steel may be scratched, but not the diamond.

Various experiments have been instituted for the purpose of determining the force requisite to disunite solids from contiguous fluids, to disunite solids from contiguous solids, and to break or to disunite the continuity of given solid. But the circumstances of temperature, purity