What then is the internal constitution of matter? Are the pores of bodies void of all substance? or are or are they pervaded by subtile and active matter? If so, what is it, and what are the laws by which it operates? It is quite certain, that until these important queries are resolved, the science of nature can never be established on the solid rock of first principles; but must remain, as heretofore, imperfect and vacillating.*

It requires no extended series of argument to prove, that whatever the cause may be which moves atoms, must also be the cause which moves the largest bodies, for the simple and obvious

It was supposed by Epicurus and his followers, that “the atoms of fluids were smooth and spherical, by which they were enabled to glide freely over each other; but that the atoms of solids were hooked," as if their forms could change on passing from the liquid to the solid state. He also maintained that the pores of bodies were void of all matter. (De Natura Rerum, book ii.) Others have supposed that the particles of bodies are glued together by an immaterial cement, as bricks are held together by mortar. (Baxter on the Immateriality of the Soul.) The Rev. W. Jones referred cohesion to the pressure of a cold ather, from the fact that liquids are converted into solids by cold. This he thought was demonstrated by the expansion of water during the process of freezing; an effect which is obviously owing to the arrangement of its particles in the crystalline form. Ampere, Berzelius, and some other modern philosophers have maintained that the atoms of bodies are endowed with electric polarity, or that their opposite sides are in different states of electricity; while the great body of chemists regard the whole subject as involved in profound obscurity.

reason that they are made up of atoms. If it be true, that cohesion, capillary attraction, and chemical affinity, be only modifications of gravity, as maintained by Newton, Laplace, Buffon, Guyton, Morveau, and other philosophers, it follows, that the whole theory of nature, whether mechanical, chemical, or physiological, is resolvable into that of atoms, and the cause by which they are surrounded, attracted and repelled, united and separated. If we are capable of discovering the cause which holds together the particles of a pebble, or crystal of ice, and can demonstrate that it is a universal constituent of ponderable matter, we are also capable of comprehending the cause which binds all things together by gravity. Newton expressly affirms, that "the drops of fluids affect a round form by the mutual attraction of their parts, as the earth affects a round form by the mutual attraction of its parts by gravity." (Opticks, book iii. page 370.)

It is self-evident, that if the particles of bodies be not endowed with inherent powers of motion, they must be impelled by some other agent;that is, they must act upon each other at a distance, without the agency of any physical tie, or by something intimately connected with them. Thus it will be found, that the primary object of science is to ascertain the cause which moves atoms, and the mode in which it produces so

many and diversified effects; that chemistry and natural philosophy are only different branches of one great science, which cannot be studied apart from each other, without departing from the unity and simplicity of nature, every operation of which is governed by the same code of physical laws, from the aggregation of a crystal to that of suns, planets, and their satellites.

It is still a problem with philosophers, whether the particles of bodies are drawn together, or pressed together. Newton supposed, that the æther, which I have shewn to be identical with the cause of heat, was more rare within the substance of dense than light bodies; and more dense in the spaces beyond them, than around their particles, by which they are pressed together. (See page 28, chap. 1.) But I have shewn the reverse of this to be the fact;-that a cubic inch of carburetted hydrogen, which is eight times the specific gravity of simple hydrogen, contains a greater amount of æthereal matter around its particles, because they are larger, and have a stronger attraction for it. For the same reason, equal volumes of olefiant gas contain more of the igneous æther around its atoms than light carburetted hydrogen, while the vapours of alcohol, æther, naphthalin, ætherine, and many other gaseous bodies, attract and retain around their particles still larger quantities, corresponding with their greater size.

I have proved, that when chlorine, or the vapours of carbon, sulphur, phosphorus, &c. are brought into contact with hydrogen, they diminish its elastic force by withdrawing from it a portion of its caloric; and that all gaseous bodies are combined chemically, with contraction of volume, by virtue of their attraction for caloric, for the same reason that steam, ammoniacal gas, and the vapours of alcohol, æther, nitrous acid, hydrocyanic acid, &c. are condensed by contact with cold water, and chemically united with the

water.

I have shewn, in the foregoing chapters, that the atoms of all bodies are surrounded with subtile and active matter, without which they could neither approximate nor recede from each other; consequently, would be passive and motionless; that the various forces, movements, and changes of form which bodies undergo, are determined by the relative proportions of æthereal and ponderable matter of which they are composed; that when the active principle predominates, they are decomposed, or expanded into gases, vapours, or even flame, which is luminous æther; but that when the ratio of gravitating matter predominates, its attraction for caloric counteracts its self-repulsive force, by which gases are chemically united into vapours, with contraction of volume and diminution of elasticity, or condensed into liquids and solids.

It still remains to prove that the cohesion of metals, rocks, and all other solid bodies, is determined by the various degrees of force with which they attract caloric; and that it is resolvable into the same cause which produces the contraction and chemical combination of gases, or reduces them to the form of liquids. If it can be established as a general law, that the particles of all bodies are held together, with forces which vary according to the different degrees of their affinity for caloric, and that this affinity varies with every change in the relative proportions of caloric and ponderable matter, the problem of attractions will be greatly simplified; for it will be evident that cohesion is not the result of pressure, as conjectured by Newton, but that contraction and expansion, density and lightness, solidity and fluidity, are modified effects of one and the same agent; in fine, that all the operations of nature depend on the relations of æthereal and ponderable matter.

A thorough comprehension of the law by which caloric is chained down in a state of intimate combination with the ponderable matter of the earth, and thus prevented from expanding throughout the universe, would banish from the science of Physics all those vague and absurd speculations, which have been founded on hypothetical data, such as innate forces, immaterial properties, occult qualities, inertia of atoms, &c.