CHAPTER II.

Chemical Attraction.

"Of the great and comprehensive laws, which rule over the widest provinces of natural phenomena, few have yet been disclosed to us." WHEWELL.

A COMPLETE history of Chemistry would embrace an account of all the molecular transformations perpetually going on throughout nature, by which matter is maintained in a state of unceasing motion, as if pervaded by a principle of universal life. Every process of combustion, solution, fermentation, putrefaction, and recombination, are only modified exertions of chemical action, by which the face of the earth is perpetually renovated, and without which, the great frame of nature would fall into an eternal sleep or death.

Whether in a practical or philosophical point of view, a perfect theory of chemistry would be of far higher importance than that of universal gravitation; for it would lead to a knowledge of all the properties of the elements by which we are surrounded, and of their application to the extension of human happiness. Yet there never was a period in the history of science, when

greater uncertainty prevailed in regard to the primary cause of chemical action, than at the present time. The celebrated Erstedt regards the science of chemistry as in the same condition now, that mechanical philosophy was in the age of Galileo, Descartes, Huygens, and Newton; and maintains that no general principle has been discovered which governs all affinities. (Sur l'Identité des Forces Chimiques et Electriques.)

Notwithstanding the recent progress of atomic chemistry, Dr. Prout observes, that this great science" is founded solely on experience, for the phenomena of which we can assign no reason." (Bridgewater Treatise, p. 29.) On the same subject, the language of Professor Whewell is still more emphatic and precise. In the concluding chapter of his Treatise on Astronomy, he states, that" no one has pointed out any common feature between chemical affinity and the attractions of which we know the exact effects; and that we are still more profoundly ignorant of the vital principle." Alas! if this be a true representation of the actual state of human knowledge, is it not high time that men should awake from their lethargy, and observe more attentively all the circumstances connected with chemical action ? It was profoundly observed by Bacon, that "in all generation and transformation of bodies, we should inquire what is added, what remains, and what is lost,-what is united, and what is sepa

rated,-what hinders, what commands, and what gives the motion." (Novum Organum.)

This is the true foundation of the inductive philosophy; careful observation, rigid analysis, the rejection of all hypotheses, and the undue authority of distinguished names, must ultimately It is doubtlead to the discovery of all causes. less an object of great practical importance to know the proportions in which the elements of ponderable matter unite to form water, alcohol, æther, acids, alkalies, salts, rocks, &c.; but it is still more important to know what the agent is, by which they are brought together and maintained in a state of intimate combination.

It is already well known, that all chemical action is resolvable into attraction and repulsion, or combination and decomposition. I have also shewn, that every particle of ponderable matter is surrounded by an active, subtile and igneous fluid, which in one proportion exerts a prodigious force of attraction for them, and thus holds them together; while in larger proportions, it separates them by a counteracting and idio-repulsive force that every change in the dimensions, powers, and aptitudes of different bodies, is attended by an addition or subtraction of this æthereal principle; that all liquids, vapours, and gases are solutions of ponderable matter in caloric, with which they are intimately united by a mutual affinity.

The proximate agency of caloric in chemical affinity would have been long since recognised, but for the difficulty of comprehending how a self-repulsive agent could become a cause of attraction. But it is self-evident, that if a globule of ice be composed of oxygen, hydrogen, and caloric; and if there be an attraction between the particles of ice and caloric, they must be held together with a force equal to that attraction; and so of all other bodies. Besides, if it were demonstrated, that some other æthereal fluid, such as electricity, surrounds the particles of ice, it must have an attraction for them like caloric, or it could not become a bond of union. It therefore follows, that in either case, the effect results from one and the same fundamental law, which involves an identity, or unity of causation. In addition to what was before stated, page 186, the following facts will further illustrate the manner in which a self-repulsive fluid becomes a bond of union between the particles of ponderable matter, which have no inherent affinity for each other.

It is well known, that the particles of æther, alcohol, and many other volatile liquids, repel each other with such force, that when the pressure of the atmosphere is removed, they fly asunder, and assume the form of elastic vapours, thus presenting the character of an idio-repulsive agent. It is also known that when the particles

of resin, charcoal, and hundreds of other bodies, are reduced to the state of an impalpable powder, like the dust of our roads after a long drought, they have little or no attraction for each other: but if they be brought into contact with the above volatile liquids, they cohere with considerable force. Why? Undoubtedly because there is a mutual attraction between the liquids and powders, which counteracts the repulsive force of the liquids, and prevents them from flying off in the form of vapour.

If the particles of dust had no cohesion for each other whatever, they would represent the condition of ultimate atoms wholly deprived of caloric, which could neither approximate nor recede from each other. At the temperature of 67° F. water is an elastic fluid in vacuo; but if a thin film of water be placed between two plates of glass in an exhausted receiver, they cohere together, because the water is more strongly attracted by the glass, than repelled by its own particles. However imperfect such illustrations may be, they are sufficient to prove that a selfrepulsive agent may become a bond of attraction to other bodies. But the fact which must for ever set this question at rest is, that the attraction of all bodies for caloric augments, cæteris paribus, in proportion as they are deprived of it, and that their cohesion augments in the same ratio.

To those philosophers who have regarded elec