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which, though it does not amount to a proof of a hypothesis where it is found, is an abundant reason for rejecting one, where it is wanting.

The vortices of Descartes, and the ether of Newton, do neither of them give any reason why gravity should be supposed to obey one law more than another; why it should be inversely as the squares, any more than the cubes, or any other power, nay, any other function, of the distances. The extreme vagueness of such hypotheses is an unsurmountable objection to them, and, even were they true, it renders them of no use whatsoever. Concerning a cause so imperfectly understood, we can never reason at all, and we derive, therefore, no advantage from knowing it to be true. The knowledge of the fact without the cause is just as valuable.

The above is the outline of Le Sage's theory; to follow it into alt its detail, and all the variety of its applications, is a task for which we are not prepared, and one quite foreign from our purpose. It is enough, if we can in any degree awaken a curiosity which the works of the author are afterwards to gratify.,

Some objections to this theory have been stated in the letters: that Le Sage received from his correspondents. Boscovich, who had a system concerning the different forces which are the cause of motion, the very opposite of what has now been laid down, one in which all contact and immediate impulse are denied, could not possibly admit the theory of gravific atoms, and has stated an objection to it, which appears to us of considerable weight The action of these atoms supposes a vast superfluity of matter, and an infinity of corpuscles, created, each; to give, at most, only a single blow, and many of them never to have any effect whatsoever. An immense multitude of atoms, thus destined to pursue their never ending journey through the infinity of space, without changing their direction, or returning to the place from which they came, is a supposition very little countenanced by the usual economy of nature. Whence is the supply of these innumerable torrents ; must it not involve a perpetual exertion of creative power, infinite both in extent and in duration? The means here employed seem greater than the end, great as it is, cans justify; and Le Sage must be allowed, if his system is rejected, to have had the merit of imagining a species of machinery more powerful and extensive than even the preservation of the universe can be supposed to require.

Another objection which, we understand from the author himself, had been made to his hypothesis is, that, were it true, a body enclosed on all sides, ought to gravitate less to the earth, than if it were in the open air. The roof or vault over head,

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would of course diminish the action of the gravific atoms that had to pass through it, and would make the body fall to the ground with less velocity than it would have done in the open air. To this it was easy to reply, that the effect here stated is real on every supposition; but is so small, that it cannot be measured in our experiments. The gravitation of a heavy body, in a room, to the roof above it, must, on the common hypothesis of attraction, diminish its weight just as much as it would be diminished by the roof's obstructing some of the gravific atoms. In both cases, the effect would be precisely the same, but too small to make any sensible diminution of the gravitation toward the great mass of the earth.

The obstruction which the gravific atoms would give to the motion of bodies, by producing a kind of resisting medium, was also objected to the doctrine of Le Sage. This might no doubt be answered, by alleging that the same effect may as well be ascribed to light, which, in this respect, is in circumstances very similar to the gravific atoms. Indecd the analogy between those atoms and the partides of light as emitted from bodies, affords the means of refuting the greater part of the objections alleged against the existence of the former. This, however, supposes that the phenomena of light are interpreted in the Newtonian inanner, or by an emanation from luminous bodies. If light is considered as an elastic fluid, the vibrations of which communicate to the eye the impressions which give rise to vision, the analogy referred to has no place. Accordingly Euler, in his letters to Le Sage, observes, that this analogy had no weight with him, as he did not believe in the emanation of light. He inclines to account for gravity from the pressure of a subtle matter composing a vortex. He is not very explicit, however, and has left us much in the dark as to his opinions on this subject. His letters are, nevertheless, very interesting, particularly that dated from Berlin, 16th April 1763.

It is a good remark of Le Sage, speaking of the analogy between light and the gravific atoms, that if all bodies were transparent, so that light was never stopped in its course, it (light) would not be perceived by us, nor apprehended to exist any more than the corpuscles. to which he ascribes the cause of gravity. We are, in truth, indebted to darkness, or the absence of light, for our idea of the latter, as a separate and in. dependent substance. Without the information thus afforded; we might be induced by reasoning to believe that there was something necessary to vision, beside the eye and the object; but we would have no proof of its existence from immediate perception, any more than we now have of the cause of gravitation

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Le Sage certainly did not borrow his notions concerning the cause of gravity from any one ; but he was not the first to whom such notions had occurred. Fatio de Duillier had, in 'some respects, anticipated the doctrine of gravific atoms; at least he had conceived a mechanical explanation of gravitation, which agreed in several particulars with that which has been described above.

The name of Fatio is well known to those who have studied the controversy between Newton and Leibnitz. He was a ma. thematician of considerable eminence, though noted for a strange departure from the character of a philosopher, by joining himself to a set of fanatics, who carried their extravagance so far as seriously to undertake the raising of the dead, Fatio, however, never published any thing on the cause of gravitation, and his treatise on it remains still in manuscript. Mr Le Sage was first informed of this in the year 1749 by Professor Cramer, not till after his essay sur les Forces Mortes, in which he treated of this subject, was communicated to the Academy of Sciences at Paris. Le Sage left nothing undone to rescue the work of Fatio from oblivion, taking much interest in the fate of a theory founded on the same principles with his own, and invented by a man of acknowledged ability. Fatio died in England in the year 1753, in Worcestershire, at the age of ninety. His manuscripts had fallen into the hands of his neighbours, and of the people with whom he lodged. Some friends of Le Sage's, in London, had the good fortune to procure them for him. He soon after depc. sited them in the library at Genera, where they still remain.

It is worth observing, that this theory of Fatio must have been known to Newton, with whom he lived in friendship, not mere. ly from a resemblance in their philosophic, but also, as has been alleged, from an agreement in their religious sentiments. Yet it is no where hinted at by Newton, even when he is engaged in inquiries on this very subject. It is probable that he did not approve of the system of his friend, who does not appear to have had the same clear views of the matter with Le Sage, nor to have had the same ingenuity in removing the objections to his theory.

A prejudice of a very unphilosophic nature, has lately prevailed in this country, against attempts of the kind made in the writings of Le Sage. It has been represented as impious, and savouring of irreligion, to offer any physical or mechanical explanation of the force of gravity.

This, we must observe, is quite a new doctrine. Newton, who was a man of true and sincere picty, thought that he was doing nothing more inconsistent with his duty, when he was endeavouring to explain the action of gravity by that of an ethe

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rial fluid, than when he demonstrated that the planets revolve in ellipses, and describe round their common focus areas that are proportional to the time. . Dr Clarke was of the same om, pinion, and has admitted, that a mechanical explanation of gravity would be of great importance in philosophy. Such an attempt is undoubtedly attended with difficulty; and perhaps we are destined to remain for ever ignorant of the cause which produces the phenomena of attraction. There can, however, be no impropriety in endeavouring, while there appear to be two kinds of causes that produce motion, to try to reduce them to one. If this is maintained to be impious, it must be on the same principle that Anaxagoras was charged with irreligion, for affirming that the planets are bodies like the earth. The same mistaken zeal has in every age opposed the same obstacles to the advancement of true philosophy.

We had almost forgot to mention the particular drift of Le Sage in the tract on the gravific atoms, which he calls Lil.com crece Neutonien. He endeavours to show, that Epicurus, with a little attention to geometry, and the possession of no more phy sical knowledge than was to be found among some of his con temporaries, might have been led, by the atomical system, to the discovery of gravitation, and of the laws of the planetary motions. The tract is very ingenious and interesting.

The subject of Teleology, or the doctrine of final causes, was one which occupied the thoughts of Le Sage, at intervals, during his whole life. Of his speculations on this subject, we are presented with a few fragments, that are in no small degree curious and interesting. The publication is by M. Reverdil, who had assisted in the composition of the work, and to whom Le Sage, in his will, left the charge of this manuscript. About the year 1740, Le Sage formed the plan of a Theory of the Ends of Nature and of Art. Wolff, who at that time taught the philosophy of Leibnitz in Germany with great reputation, in his treatise on logic, recommended the theory of Ends to be treated under the name of Teleology ; and this term was adopted by Le Sage. M. Reverdil informs us, that Le Sage was confirmed in his design, by finding that some men of great celebrity had about that time conspired to combat the doctrine of final causes ; some of them on a principle of universal scepticism ; others to give weight to the proofs of the existence of God derived from other sources ; and many, struck no doubt with the weak and childish arguments that had been often maintained on this subject. Le Sage wished to oppose all these, and in particular the latter, by showing that the theory of final causes ka

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was not necessarily of the vague and unsatisfactory nature just alluded to.

The greater part of the works,' says he, “ that have made their appearance on this subject, contain principles fo vague and unsupported, observations fo puerile and detached, and reflexions fo common-place and declamatory, that it is not wonderful if they produced an effect the direct opposite of that which was intended. A theory of Ends, or Final Causes, might be given, exempt from these great defects ; embracing the objects both of nature and art ; furnishing, first, rules of synthesis for the composition of a work, when the ends and means were both given ; and, next, rules of analysis for discovering the intention of an artist, from the examination of his works.?

M. Reverdil has given us only a few fragments from the treatise which had been drawn up conformably to this plan. Those that follow will show in what manner Le Sage had endeavoured to avoid the faults which he has reprobated in others.

• A wise cause must have respect to the smallest degrees of good, because, if they are not infinitely small, the amount of the whole may be of importance ; so that, if they were neglected, a confiderable quantity of evil might arise,

. There is nothing incongruous, therefore, in supposing the Divine Wisdom exercised in determining the curvature of the wing of a scarabæus, or in planning the cells of a bee-hive. It may be true, that it imports little to the universe, whether a scarabæus Ay, with more or Jess ease, or a bee, employ its wax with the greatest pofsible frugality. It imports much, however, to the scarabæus or the bee, and, on that account, is an object not unworthy of the attention of the Creator. If the precision in the structure of the wings or cells of these infects is useful for any purpose, however small, that utility, multiplied by the number of all the scarabæi, and all the bees which have been, which are, and which are to be, may become of a considerable amount.

• When the execution of any purpose gives rise to inconvenience which admits of remedy ; of all the remedies that can be applied, that is the best which rises out of the evil itself, because it is always at hand when wanted, and is sure to possess the necessary strength. Such remedies are sometimes to be met with in the arts. It was thus that a hint of Monfieur the Prince of Conti, furnished Reaumur with the means of admitting the necessary quantity of air into his furnaces for hatching chickens, by making the heat of the furnace open the door of a register. The girdiron pendulum of Graham, is an instance of the {ame kind. .

• In nature, the contraction and dilatation of the pupil of the eye, is a most remarkable instance of an inconvenience corrected by its own operation.

• When all the accidents which happen to a work derange it; and when all those that can happen to it have a tendency to do the

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