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 our 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 inextended points 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, 1 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 have 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 forma tion 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 *This outline is given more at length in the author's Prolegomena to his translation of "The Nature of Things," p. cix. and following

appear competent, and which were not accounted for under the old system, Epicurus supposed that some atoms were occasionally possessed of a third, by which, in some very small degree, they descended in an oblique or curvilinear direction, deviating from the common and right line anomalously; and in this respect resembling the oscillations of the magnetic needle.

These infinite groups of atoms, flying through all time and space in different directions, and under different laws, have interchangeably tried and exhibited every possible mode of rencounter; sometimes repelled from each other by concussion, and sometimes adhering to each other from their own jagged or pointed construction, or from the casual interstices which two or more connected atoms must produce, and which may be just adapted to those of other figures, as globular, oval, or square. Hence the origin of compound and visible bodies; hence the origin of large masses of matter; hence, eventually, the origin of the world itself. When these primary atoms are closely compacted, and but little vacuity or space lies between, they produce those kinds of substances which we denominate solid, as stones and metals; when they are loose and disjoined, and a large quantity of space or vacuity is interposed, they exhibit bodies of lax texture, as wool, water, vapour. In one mode of combination they form earth; in another, air; and in another, fire. Arranged in one way, they produce vegetation and irritability; in another way, animal life and perception. Man hence arises, families are formed, societies are multiplied, and governments are instituted.

The world, thus generated, is perpetually sustained by the application of fresh tides of elementary atoms, flying with inconceivable rapidity through all the infinity of space, invisible from their minuteness, and occupying the posts of those that are as perpetually flying off. Yet nothing is eternal or immutable but these elementary seeds or atoms themselves. The compound forms of matter are continually decomposing and dissolving into their original corpuscles; to this there is no exception: minerals, vegetables, and animals, in this respect all alike, when they lose their present make, perishing for ever, and new combinations proceeding from the matter into which they dissolve. But the world itself is a compound though not an organized being; sustained and nourished, like organized beings, from the material pabulum that floats through the void of infinity. The world itself must, therefore, in the same manner, perish: it had a beginning, and it will have an end. Its present crasis will be decompounded; it will return to its original, its elementary atoms; and new worlds will arise from its destruction.

Space is infinite, material atoms are infinite, but the world is not infinite. This, then, is not the only world, nor the only material system that exists. The cause that has produced this visible system is competent to produce others it has been acting perpetually from all eternity; and there are other worlds, and other systems of worlds, existing around us.

Those who are acquainted with the writings of Sir Isaac Newton and Mr. Locke, will perceive in this sketch of the Atomic philosophy the rudiments of a very great part of their own systems, so far as relates to physics; we may, indeed, fairly regard them as offsets from the theory before us, cleared in a very great degree of its errors, and enlarged in their principles, and fortified by more recent observations and discoveries. I must, for the present, confine myself to the following quotations from the first of these high ornaments of our country. "All things considered," says Sir Isaac, "it seems probable that God, in the beginning, formed matter in solid, massy, hard, impenetrable, moveable particles; of such sizes and figures, and with such other properties, and in such proportion to space as most conduced to the end for which he formed them." So again: "While the primitive and solid particles of matter continue entire, they may compose bodies of one and the same nature and texture in all ages; but should they wear away, or break in pieces, the nature of things depending on them would be changed. Water and earth, composed of old worn particles and fragments of particles, would not be of the same nature and texture now, with water and earth composed of entire particles at the beginning; and therefore, that nature may be lasting,

the changes of corporeal things are to be placed only in the various separations, and new associations and motions of these permanent particles: compound bodies being apt to break, not in the midst of solid particles, but where those particles are laid together, and touch only in a few points."

The Epicurean doctrine, moreover, of a flux and reflux of elementary particles exterior to every material system, perpetually feeding and replenishing it, and carrying off its dissolved and rejected rudiments, bears no small resemblance to the ethereal medium of Sir Isaac Newton; and, in its law of action, has been singularly revived within the course of the last six years by Professor Leslie, in his principles of impulsion, as detailed in his “Inquiry into the Nature of Heat." It is a doctrine, also, peculiarly coincident with Dr. Herschel's recent theory of nebulæ, or milky ways in the heavens, which, contrary to his own earlier opinions, and those of former astronomers, who ascribed such appearance to the mixed light thrown forth from clusters of stars too remote to be reached by the best telescopes, he now resolves, as we shall have occasion to show more minutely in due time, into masses of a luminous fluid, existing independently of all stars or planets, though originally, perhaps, emitted from them; aggregated by a variety of causes that tend to give its minute particles unity; sometimes forming new stars by its condensation, and often feeding and regenerating those that are exhausted.

Such is a brief survey of the chief theories of the primitive or elementary substance of matter which have been offered in ancient or modern times; from a combination of the different particles of which, in different modes and proportions, and under the operation of different laws, all sensible bodies are supposed to have proceeded.

Of sensible bodies thus produced, some, however, in direct repugnancy to the Atomic philosophy, whether of ancient or more recent times, have been very generally conceived to have been formed first; to be peculiarly simple in their composition, indecomposable by any known powers in their structure, and to be the basis of all other bodies, or those from which all other bodies proceed, by different unions and modifications: and hence such substances have been denominated constituent principles, or constituent elements; concerning the kind and number of which, however, we have had almost as many opinions offered as concerning the origin and nature of the primitive principles themselves.

Thus, among both the ancients and the moderns, sometimes fire, sometimes air, sometimes earth, and sometimes water, has been considered as the sole constituent element or source of things. Sometimes two of these substances have been thus denominated, and sometimes three; but more generally the whole. Occasionally, indeed, a fifth and even a sixth have been added to the number, as cold and oil, each of these having at times been considered as simple and indecomposable substances: while, under the old Atomic system, and especially as improved by Epicurus, all such principles were completely swept away, and no one sensible substance whatever was conceived to be better entitled to the character of a constituent principle than another; the whole equally flowing from peculiar modifications and combinations of the primitive or elementary principles-the RERUM PRIMORDIA—and equally resolving into them upon decomposition.

Of these different theories, the greater number are scarcely worth examining; and I shall only therefore observe, that for that which supposes the existence of four distinct elements, fire, air, earth, and water, and which for ages has been in almost universal acceptation, and would have been so still but for the recent discoveries of chemistry, we are indebted to Empedocles. This celebrated philosopher, and very excellent poet, flourished about four centuries before the Christain era. His opinions, like those of almost all the earliest sages, were given in metre, in a didactic poem, "ON NATURE," of which only a few fragments have descended to our own times. He was a native of Sicily, and his talents and his country are celebrated by Lucretius, who was, nevertheless, of a very different school of philosophy, in verses so

elegant and so descriptive, that I cannot refrain from presenting you with a literal but very humble translation of them; introduced, more especially, as they are, with observations upon different rival philosophers, who employed one, two, and various other numbers of the commonly esteemed elements, and in various combinations, as the basis of their respective theories.

Nor wanders less the sage who AIR with FIRE

Would fain commix, or limpid STREAM with EARTH;
Or those the whole who join, FIRE, ETHER, EARTH,
And pregnant SHOWERS, and thence the world deduce.
Thus sung EMPEDOCLES, in honest fame
First of his sect; whom AGRIGENTUM bore
In cloud-capp'd SICILY. Its sinuous shores
Th' IONIAN main, with hoarse unwearied wave,
Surrounds, and sprinkles with its briny dew;
And, from the fair EOLIAN fields, divides
With narrow frith that spurns th' impetuous surge.
Here vast CHARYBDIS raves; here ETNA rears
His infant thunders, his dread jaws unlocks,
And heaven and earth with fiery ruin threats.
Here many a wonder, many a scene sublime,
As on he journeys, checks the traveller's steps;
And shows, at once, a land in harvests rich,
And rich in sages of illustrious fame.

But naught so wond'rous, so illustrious naught,
So fair, so pure, so lovely can it boast,

EMPEDOCLES, as thou! whose song divine,

By all rehears'd, so clears each mystic lore,

That scarce mankind believ'd thee born of man.

Yet e'en EPEDOCLES, and those above

Already sung, of far inferior fame,

Though doctrines frequent from their bosoms flow'd

Like inspiration, sager and more true

Than e'er the PYTHIAN maid, with laurels crown'd,
Spoke from the tripod at APOLLO's shri e;

E'en those mistook the principles of things,

And greatly wander'd in attempt so great.

Let our controvertists of the present day learn a lesson of liberality from this correct and polished reasoner, whose own theory is well known to have been that of Epicurus, to which I have just adverted, namely, that one substance is just as much entitled to the character of a constituent element as another, and that every thing equally proceeds from, and in turn is resolved into, the primitive and invisible atoms or principles of matter.

It is to this theory alone that all the experiments of modern chemistry are giving countenance. Air, water, and earth, suspected to be compounds in the time of Epicurus, have been proved to be such in our own day; while of the actual nature of heat or fire, mankind are just as uninformed now as they were then.

In the process, however, of destroying these supposed elements, chemistry has occasionally seemed to detect others; and hence, instead of air, fire, earth, and water, as simple or indecomposable substances, we have had phlogiston, acids, and alkalies; sulphur and phosphorus; oxygen, hydrogen, nitrogen, and carbon, progressively arising before us, and laying claim to an imperishable existence. All of them, however, have fallen, or are falling in their turn, without having lived long enough to reach the common age of man; all of them have been proved, or reasonably suspected, to be compounds of other substances, that may yet, perhaps, be detected to be compounds of something beyond. Even oxygen, the most brilliant of the whole, the boasted discovery of Lavoisier, and out of which he was supposed to have built to his own memory "a monument more durable than brass," has had its throne shaken to its foundation by Sir Humphry Davy, and is at this moment, like the Roman empire in its decline, obliged to divide its sway with a new and popular power, which this last celebrated chemist has denominated ch orine; while of the more subtle and active agents, light, caloric, the magnetic and electric fluids, we know nothing but from their effects, and can only say of each-stat nominis umbra.

Is physical science, then, a vain show?-a mere house of cards, built up for the sole purpose of being pulled down again ?-Assuredly not. The firm