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am at a loss how else to characterize it: for it has been minutely ascertained within the last ten or twelve years, by an almost infinite variety of accurate and well-defined experiments by Higgens, Dalton, Gay Lussac, and Davy, that the combinations and separations of all simple bodies are conducted in a definite and invariable ratio of relative weight or measure ;* as that of one part to one part, one part to two parts, one to three, or one to four; and, consequently, that every change in the compound thus produced, whether of addition or diminution, is a precise multiple or divisor of such ratio; or, in other words, that the different elementary bodies which enter into such compounds can never unite or separate, never lay hold of or let go each other, in any other proportions.

Let us exemplify this remark by a familiar instance or two. It is now well known to every one that the calxes, oxides, or, as they are often called, rusts, of metals, consist of a certain portion of oxygen with a certain portion of, the metal, which is thus converted into a calx or oxide. It is also known in the present day to most persons, that the greater number of metals are possessed of two or more kinds of oxides, produced by a union of different proportions of the oxygen and the metal, and often distinguishable even by their colour; as minium or red lead, and ceruse or white lead, which are equally oxides of the metal whose name they bear. Now, in whatever proportion the oxygen unites with the metal to produce an oxide of one kind, it invariably unites by a multiple or divisor of the same proportion to produce every kind of oxide belonging to the same metal. Thus we have discovered not less than four different oxides of antimony in different parts of the world: the lowest or simplest of them contains 41 parts of oxygen to 100 parts of metal; the next simplest contains 18 parts of oxygen to 100 parts of metal, which is four times 44; the third oxide consists of 27 parts of oxygen to 100 parts of metal, which is six times 4j; and the fourth oxide, 36 parts of oxygen to 100 parts of metal, which is eight times 4i. So tin, which possesses three discovered oxides, has for its lowest the proportion of 7 parts of oxygen to 100 parts of metal; for its second oxide, 14 parts of oxygen to 100 parts of metal, which is twice 7; and for its highest, 21 parts of oxygen to 100 parts of metal, which is three times 7. I have given the proportions in round numbers; but if I were to use the fractions that belong to them, the comparative results would be precisely the same. Nor can we possibly combine these substances in any other proportions, so as to produce oxides; for the corpuscles of which they consist will not lay hold of or let go each other in any other ratios. It is possible that we may hereafter detect an oxide of antimony consisting of a less proportion of oxygen than 4i; but if we ever should, we are confident beforehand that such proportion will be 21. It is also possible that we may meet with an oxide containing more than 4i and less than 18 parts of the oxygen in 100; but if we should do so, we can nearly anticipate that such proportion will be 9. And hence, as these proportions, though constantly true to their respective series, are constantly diversified in different substances, their radical figures or numbers may be employed, and now actually are employed, and that very generally, and in perfect coincidence with the system of the Pythagorists, as synonymesof the simple forms or substances whose progressive character they describe. This curious coincidence of ancient and modern philosophy, for at present I will call it nothing more, I cannot but regard as a very marvellous fact; and am not a little surprised that it should not hitherto have occurred, as it does not appear to have done, to the minds of any of those learned and ingenious chemists who have chiefly been employed in applying and building up the discovery. And it is not the least important part of this discovery, that not only in the union or separation of simple substances, but in all wellknown and more complicated compounds, so far as the experimental series has been carried, the elementary bodies which enter into them exhibit pro- * The only apparent exception I am aware of to this general principle la In the combination of the el*. Bienta of M. Dulong's detonating substance, or azotane, as described by sir Humphry Dary, Foil. Trans, ftr 1813, p. 840: and It to bene* probable that we are not yet put into possession of the proper results.

portions equally definite and invariable; thus affording another proof of close connexion between the phenomena of nature and the occasional developements of revelation; the philosopher beholding now, as the prophet beheld formerly, that the Almighty architect has literally adjusted every thing by weight and measure; that he has measured the waters and meted out the heavens, accurately comprehended the dust of the earth, weighed the mountains in scales and the hills in a balance.

LECTURE III.

ON THE ELEMENTARY AND CONSTITUENT PRINCIPLES OF THINGS.
(The subject continued.)

The few steps we have hitherto taken in the wide and magnificent scope before us have only led to an establishment of two or three fundamental axioms, of no small importance in the science of physics, and to a developement of two or three of the most ingenious and most popular hypotheses of former times, invented to account for the origin of the world around us, and the elementary and constituent principles of things: especially the hypothesis of numbers, as proposed by Pythagoras, and that of ideas, as proposed by Plato; and their application to primary and incorporeal matter, in order to endow it with form and quality. There are yet two or three other hypotheses upon the same subject that amply demand our attention, and are replete with an equal degree of ingenuity and fine imagination; especially the Peripatetic and the Atomic, or that of Aristotle and that of Epicurus; and we have also to trace out the relative degree of influence which each of these has exerted on the philosophical theories of later times.

Aristotle had too much penetration not to see that the hypothesis of Plato was just as inadequate as that of Pythagoras to a solution of the great question concerning the production of the visible world: and he proposed a third scheme, which has also had its share of popularity. According to this remodelled plan, the sensible universe is the result of four distinct principles, —intelligence, matter, form, and privation; which last term is little more than a mere synonyme for space or vacuum; and thus far the theory of Aristotle chiefly differs from that of Plato, by interweaving into it his fourth principle, derived from Democritus, and the other Atomic philosophers, and which he seems to have added to it with a view of providing a proper theatre for the two principles of form and matter to move in. He supposes all these to have equally existed from eternity; and the three last to have been eternally acted upon or thrown into a definite series of motions, upon which alone the existence and harmony of things are dependent, by the immutable and immaterial principle of intelligence, whose residence he places in the purest and loftiest sphere or circle of the heavens; a sphere that in its vast embrace comprehends ten lower or subordinate spheres, that lie between itself and the earth, which forms the centre of the whole, and, in conjunction with the earth, constitutes the universal world.

This Supreme Intelligence Aristotle conceived to be in himself for ever at rest; and the tranquil and peaceable sphere in which he resides he denominated the empyreum or heaven of bliss. But though enjoying eternal rest himself, he communicates motion, necessarily and essentially, upon this theory, to the sphere immediately below him; as this, in its turn, communicates it in different directions, and with different velocities, to the other spheres that revolve within its range ;* whence the sphere thus earliest receiving motion, and nearest to the empyreum, Aristotle denominated the parMum Mobile, or first moving power: it constituted the tenth in the regular series; the ninth, or that which lies next to it, being denominated the crys

• Oldf. Usft. lib. T. MM. U. Art*. PUji. M>. 1. cip. J, 4. De Cel. Ut>. a. cap. 11L

talline heavens; the eighth, the starry sphere, or heavens; and the remaining

.seven deriving their names from, and being appropriated to, the different revolutions of the different planets, as Saturn, Jupiter, Mars, Apollo or the sun, Venus, Mercury, and Diana or the moon: the earth, forming the centre of the whole, being an imperfect sphere, with a larger proportion of matter at the equator; on which account the earth was conceived to turn on her axis in a rocking motion, revolving round the axis of the ecliptic, and making the stars appear to shift their places at the rate of about one degree in seventy-two years. According to which calculation, all of them will appear to perform a complete revolution in the space of 25,9-20 years, and, consequently, to return to the precise situation they occupied at the commencement of such period. This period was hence denominated the Annus Maonus, or Great Year, and not unfrequently the Platonic Tear, as the same kind of revolution was in some measure taught also by Plato.

The motory power, thus impressed by the intelligent moving principle, not voluntarily but by necessity, upon the different heavenly spheres, and fmally npon the earth, and productive of that catenation of effects which is equally without beginning and without end, Aristotle denominated Nature, and thus furnished us with a word, which has for ages been so extensively made use of, that, though there is nothing in all language more imprecise, there is nothing we could spare with more inconvenience. The same term, indeed, is occasionally employed by Plato, but in a sense still less definite if possible, and at the same time still less comprehensive.

On the revival of literature, this theory, together with the other branches of Peripatetic science, was chiefly restored and studied; and continued, indeed, to be generally adhered to for upwards of a century after the publication of the Copernican system; which is well known to have at first experienced but a very cold and inhospitable reception from the literary world. And it is hence this theory that is principally adverted to and described in the productions of all the early poets as well as philosophers of every part of modern Europe. And so complete was the triumph of the Peripatetic school in alt its doctrines throughout Christendom, at this period, that Melancthon makes it a matter of complaint that, even in the sacred assemblies, parts of the writings of Aristotle were read to the people instead of the Gospel. Even Milton himself, though born considerably more than a century after Copernicus, wavers as to the propriety of adopting his hypothesis of the heavens, and hence, in his Paradise Lost,* leaves it doubtful which of the two, the new or the old, ought to be preferred. The best and most splendid description of the Aristotelian theory that I have ever met with is contained in the Lusiad of Camoens: the whole is too long for quotation, but I may venture to affirm, that you will be pleased with the following lines from Mr. Mickel's very spirited version of the Portuguese bard, as delineating the different heavenly spheres that were supposed, as I have already observed, to lie one within another, like the different tunics of an onion:—

These spheres behold: the first In wide embrace

Surrounds the lesser orbs of various Dice;
The Smpykkan this, the holiest heaven,
To the pure spirits of the blest is given:
No mortal eye its splendid rays may bear,
No mortal bosom feel the raptures there.
The earth, in all her summer pride array'd.
To this might seem a dark sepulchral shade.
Unmov'd It stands.—Within its shining frame,
In motion swifter than the lightning's flame,
Swifter than sight the moving parts may spy,
Another sphere whirls round its rapid sky:
Hence Motion darts its force, impulsive drawn,
And on the other orbs impresses laws-t

These hypotheses are abstruse, and perhaps ill calculated to afford amusement; but in a course of physical study they ought by no means to be ovrr

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looked. Abstruse as they are, the one or the other of them is interwoven with the whole range of classical literature, and, as I have already remarked, held the ascendant in the horizon of metaphysics till within the last two centuries; and I have dwelt upon them the rather, because, much as we still hear of them, and find them adverted to in books, I am not acquainted with any work whatever that gives any thing like a clear and intelligible summary of their principles. Their more prominent defects are, in few words, as follows: Independently of conveying very imperfect and erroneous views of the creation, they equally concur in reducing matter, notwithstanding its pretended eternal existence, to a nonentity, and confound its properties with those of pure intelligence, by giving to numbers, ideas, or a mere abstract notion, real form and existence. The most powerful advocate of the Platonic theory, in modern times, was the very excellent Bishop Berkeley; who, in the true spirit of consistency, and with a boldness that no consequences could deter, openly denied the existence of a material world, and thus reduced the range of actual entities from three to two, an intelligent first cause, and intellectual forms or ideas, and gave the death-blow to the system by avowing its necessary result.

In modern times, however, as I have already hinted at, the infinite divisibility of matter has for the most part been supported upon different grounds, and philosophers have involved themselves in the same fatal consequences, by a much shorter process of reasoning. No compound or visible bodies, it is well known, ever come into immediate contact with each other, or influence each other by means of simple solidity. The earth is affected by the sun, the moon by the earth; the waters of the earth by the moon. Light is reflected from substances to which it directs its course, at a distance, and without impinging upon them. The particles of all bodies deemed the most solid and impermeable, are capable of approaching nearer, or receding farther from each other, by an application of different degrees of cold or heat. We can, hence, it is said, form no conception of perfect solidity; and every phenomenon in nature appears to disprove its existence. The minutest corpuscle we can operate upon is still capable of a minuter division, and the parts into which it divides, possessing the common nature of the corpuscle which has produced them, must necessarily, it is added, be capable of a still farther division; and as such divisions can have no assignable limit, matter must necessarily and essentially be divisible to infinity.

Such was the reasoning of Des Cartes, and of the numerous host of philosophers who attached themselves to his theory about the middle of the seventeenth century. The argument, indeed, is highly plausible; but it was soon obvious, that, like the Grecian incorporeity of matter, it leads to a pure nonentity of a material world: for that which is essentially unsolid and infinitely divisible, must at length terminate in nothing. And hence, Leibnitz attempted to amend the system, about half a century, and Boscovich, about a century afterward, by contending, as indeed Zeno is supposed to have done formerly, that matter has its ultimate atoms, or monads, as they were denominated by Leibnitz, from the language of Pythagoras, beyond which it is altogether indivisible; and that these ultimate atoms or monads are simple inextended points, producing, however, the phenomenon of extension, by their combination, and essentially possessed of the powers of attraction and repulsion.

There is such a charm in novelty, that it often leads us captive in despite of the most glaring errors, and intoxicates oui judgment as fatally as the cup of Circe. It is upon this ground alone we can account for the general adoption of this new system, when first proposed in its finished state by Boscovich, and the general belief that the Gordian knot was at length fairly united, and every difficulty overcome. It required a period of some years for the heated imagination to become sufficiently cool to enable mankind to see, as every one sees at present, that the difficulties chargeable upon the doctrine of an infinite divisibility of matter are not touched by the present theory, and remain in as full force as before its appearance. If the monads, or ultimate points of matter here adverted to, possess body, they must be as capable of

extension, and consequently of division, as material body under any other dimension or modification: if they do not possess body, then are they as much nonentities as the primal or amorphous matter of Plato or Pythagoras. Again, we are told that these points or monads are endowed with certain powers; as those, for example, of attraction and repulsion. But powers must be the powers of something: what is this something to which these powers are thus said to appertain? If the ultimate and inextendedpoints before us have nothing but these powers, and be nothing but these powers, then are such powers powers of nothing, powers without a substrate, and, consequently, as much nonentities as on the preceding argument. Visible or sensible matter, moreover, it is admitted by M. Boscovich and his disciples, is possessed of extension; but visible or sensible matter is also admitted to be a mere result of a combination of inextended atoms:—how can extension proceed from what is inextended ?—of two diametrical opposites, how is it possible that either can become the product of the other?

It is unnecessary to pursue this refutation. The lesson which the whole of such fine-spun and fanciful hypotheses teach us, and teach us equally, is, that it is impossible to philosophize without a firm basis of first principles. We must have them in physics as well as in metaphysics,—in matter as well as in morals; and hence the best physical schools in Greece, as well as in more modern times,—those which have contended for the eternity of matter, as well as those which have contended for its creation out of nothing,—have equally found it necessary to take for granted, what, in fact, can never be proved, that matter in its lowest and ultimate parts consists of solid, impenetrable, and moveable particles of definite sizes, figures, and proportions to space; from different combinations of which, though invisible in themselves, every visible substance is produced.

This theory, which has been commonly distinguished by the name of the Atomic philosophy, was first started in Greece by Leucippus or Democritus, and afterward considerably improved by Epicurus; and as it bears a striking analogy to many of the features which mark the best opinions of the present day, and has probably given them much of their colour and complexion, if it have not originated them, I shall take leave to submit to you the following outline of it:—•

The Atomic philosophy of Epicurus, in its mere physical contemplation, allows of nothing but matter and space, which are equally infinite and unbounded, which nave equally existed from all eternity, and from different combinations of which every visible form is created. These elementary principles have no common property with each other: for whatever matter is, that space is the reverse of; and whatever space is, matter is the contrary to. The actually solid parts of all bodies, therefore, are matter; their actual pores space; and the parts which are not altogether solid, but an intermixture of solidity and pore, are space and matter combined. Anterior to the formation of the universe, space and matter existed uncombined, or in their pure and elementary state. Space, in its elementary state, is absolute and perfect void; matter, in its elementary state, consists of inconceivably minute seeds or atoms, so small that the corpuscles of vapour, light, and heat are compounds of them; and so solid, that they cannot possibly be broken or abraded by any concussion or violence whatever. The express figure of these primary atoms is various: there are round, square, pointed, jagged, as well as many other shapes. These shapes, however, are not diversified to infinity; but the atoms themselves of each existent shape are infinite or innumerable. Every atom is possessed of certain intrinsic powers of motion. Under the old school of Democritus, the perpetual motions hence produced were of two kinds: a descending motion, from the natural gravity of the atoms; and a rebounding motion, from collision and mutual clash. Besides these two motions, and to explain certain phenomena to which they did not

• Tol* outline Is gWen mora at length in the author'a Prolegomena to hta translation of " The Nature of Things," p. ebu and following

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