mon coal is an instance of this combination. The supporters of combustion are substances, not of themselves combustible, but are necessary to the process; that is, no combustion can ever take place, without one or other of the supporters of combustion being present. There are only seven known supporters of combustion; viz. oxygen gas, atmospheric air, nitrous oxyd, nitric oxyd, nitric acid, and oxymuriatic acid (or chlorine).

2. Whenever we burn a combustible body in order to procure heat, a continued stream of atmospheric air flows towards the fire-place, to occupy the vacancy left by the air that has undergone decomposition, which in its turn becomes decomposed also. Hence a supply of caloric is furnished without intermission, till the whole of the combustible is saturated with oxygen. An Argand's lamp is constructed upon this principle, that a current of air hastens combustion: for in consequence of this perpetual supply of oxygen, the air is renewed every moment, and produces sufficient heat to burn the smoke as it is formed. The smoke which arises from a common fire is chiefly water in the state of vapour, with a mixture of carburetted hydrogen and bituminous substances; part of the water comes from the moisture of the fuel; the other part is formed during combustion, by the union of the hydrogen of the combustible with the oxygen of the atmosphere.

XIII. ATTRACTION, REPULSION, and AFFINITY. 1. Attraction. Whenever the force of attraction operates between particles of the same species, it is called the attraction of cohesion, or the attraction of aggregation; but when between the particles of different qualities and elements, it is then called chemical attraction, or affinity of composition. It is from the attraction of cohesion that a drop of water is always spherical, and that small particles of quicksilver are constantly of a globular figure. In consequence of the same species of attraction, particles of water and other liquids ascend in capillary tubes. It may be said that the particles of all bodies are possessed of the inherent property of attracting each other, which causes them to adhere, and preserves the various substances around us from falling in pieces. The nature of this wonderful property is entirely unknown. There are different kinds of aggregation; solid, soft, liquid, and gaseous. A

stone is an instance of the first, jelly of the second, water of the third, and atmospheric air of the last.

2. Repuls on. The only kinds of repulsion that can be exhibited to the senses, are those of electricity and magnetism; but it is insensible repulsion with which chemists are more particularly concerned. The chief example of this latter kind that we are acquainted with, is the repulsion of the particles of caloric among themselves, which repulsion would constantly tend to infinite separation, were it not for a chemical union, which, by an irrevocable law of nature, they form with the first surrounding body: for by that law, the particles of caloric cannot exist in an isolated state.

3. Affinity. Chemical affinity takes place only between the ultimate molecules of bodies; while the attraction of cohesion remains superior to that of affinity, no other union can take place but that whenever caloric has sufficiently diminished this attraction in any substance, the particles are then at liberty to form new combinations, by their union with the particles of other bodies.

The ingenuity of the chemical student may be pleasingly exercised, by the endeavour to explain the nature of the changes and the causes of the phenomena which occur in different chemical processes;-such are the formation of PYROPHORI by the exposure of sulphate of alumine, of copper, of iron, or of zinc, with charcoal, sugar, honey, or flour, to a red heat; the substance thus formed taking fire on being exposed to the air :-of Baldwin's PHOSPHORUS formed by the exposure of nitrate of lime to a considerable heat-of Canton's phosphorus formed by a similar treatment of sulphur and oyster shells,-the rapid combustion of different bodies in oxygen gas-the luminous appearances and detonating power of PHOSPHORUS in different combinations, the formation of phosphoric matches, bottles &c.--the extraordinary detonating properties of the substances called hyperoxymuriates, in which chlorine exists, -the process of wet-gilding as invented by Mrs. Fulhame --the several instances of remarkable changes of colours by different admixtures and the formation of sympathetic inks-the effects produced by different processes in the arts of dyeing, calico printing, glass-making, &c. &c.

Select Books on Chemistry.

Parkinson's Chemical Pocket Book, 12mo, Parkes' Chemical Catechism, 8vo. an excellent elementary work, to which this chapter is indebted. Conversations on Chemistry, 2 vols. 12mo. Accum's Chemistry, 2 vols. 8vo. Dr. Thomson's Elements of Chemistry, 8v0. Nicholson's Dictionary of Chemistry, 8vo. Dr. Henry's Epitome of Chemistry, 8vo. Those who may have leisure or inclination to study this science at large, may successfully prosecute their studies in Dr. Thomson's System of Chemistry, 4 vols. 8vc. or Mr. Murray's System of Chemistry, 4 vols. 8vo. and Appendix. Davy's Elements of Chemical Philosophy svo.

544

PART VIII.-Philosophy, Sciences, and Arts.

CHAP. I.-METAPHYSICS OR ONTOLOGY.

1. THE mode in which authors have treated of metaphysics, is as various as their definition of the term. One author, under the form of a treatise of metaphysics, presents us with a discussion on abstract words, their meaning and application; another, with an inquiry into the faculties and operations of the human mind; a third, with a volume of theology, a dissertation on the being and attributes of God, and the nature of spiritual and celestial intelligences; and a fourth, with a treatise of ethics or moral philosophy. Yet subtle, indefinite, and evasive, as this science seems to be, there are some subjects which the learned have agreed in calling metaphysical: such were the discussion between Clarke and Leibnitz concerning the free agency of man;--the disputes concerning identity and diversity-and those upon the origin of evil. In Cudworth's Intellectual System, metaphysics are introduced with propriety and ability. Not a single discovery seems to have been added to this science since the days of Plato.

2. Metaphysics has been defined by a writer deeply read in ancient philosophy, "the science of the principles and causes of all things existing." Hence it is that mind or intelligence, and especially the Supreme Intelligence, which is the cause of the universe, and of every thing which it contains, is the principal subject of this science.

3. Metaphysical Theology inquires into the existence. of a God, makes the most rational supposition concerning his divine essence, and forms ideas of his attributes and perfections. God manifests himself in every part of nature. in our reasonings on the necessity of such a being by

metaphysics we have only to descend from the most simple ideas, to the most compound, and from thence to re-ascend by a chain of reasonings, from the creature up to the author of the creature, and of all nature: and we shall find that the result of all these operations of the mind will constantly be the necessity of the existence of a God: and we may at all times determine, though very imperfectly, from the weakness of our discernment, what that Supreme Being must be by positively determining what he cannot be.

4 Metaphysics, therefore, while it concurs to furnish new proofs on this subject, or to elucidate and establish those which are already known, must prove of inestimable value to mankind. The word originated with Aristotle, who has termed a treatise which chiefly relates to the intellectual world, and which is placed after his physics, μSTA TU QUOIXA. So that it may mean either something" beyond physics," or merely an appendix to his physics" or natural history. 5. The Cartesian Philosophy was so called from Des Cartes, the founder. By introducing geometry into physics, and accounting for natural phenomena from the laws of mechanics, he did infinite service to philosophy, and contributed to free it from that rust, which during long succession of ages it had contracted. To him, in some measure, is owing the present system of mechanical, and even Newtonian philosophy. Des Cartes was a native of Bretagne, and born in the year 1596.

6. Malebranchism is the doctrine of father Malebranche, a priest of the oratory of France. Malebranchism is contained in his Enquiry after Truth.' M. Fontenelle says, that it is full of God; that God is the only agent, and that too in the strictest sense; all power of acting, all nations belong immediately to him, &c. The manner in which Malebranche would reconcile religion to his system of philosophy is seen in his Entretiens Chrétiennes ; in which

he

proves the existence of God-the corruption of human nature by original sin-the necessity of a mediator, and of grace. His doctrine is, in other instances, ill-grounded, and even dangerous and subversive of religion. Upon the whole, Malebranchism is nearly the same with Cartesianism, and like that, has been opposed by many French authors, but by none so ably, as by our own countryman, Mr. Locke.