by the learned Profeffor, that nothing can be inferred concerning it. It is indeed fo little known to him, that he mistakes the name of the author, afcribing it to M. de Sauffure, instead of M. Le Sage.

M. Saussure,' he says, accounts for attraction, by supposing that all space is filled with particles of matter, moving rapidly in all directions; and that the particles which fall on the opposite sides of any two bodies, in lines parallel to the line joining their centres, will impel the bodies towards each other, the sides next each other not being so acted upon. But, in this case, the moving force of each body would depend on the surfaces of the bodies; whereas it ought to be as the quantity of matter in each respectively. This consideration, therefore, without entering into any further examination of this hypothesis, is sufficient to show that it cannot be admitted. ' P. 13.

Now, all this, we muft obferve, is extremely incorrect. The main excellence of the fyftem here alluded to, is, that it explains why gravity follows the direct ratio of the quantity of matter, as well as the inverfe of the fquare of the diftance; and if Mr. Vince had derived his knowledge of it from the account given by the author himself, he would have feen, that there is no room for the objection, on the strength of which he ventures, without examination, to reject the fyftem altogether. We have often thought, that there is no country in the fame ftate of civilization, where knowledge, that is the growth of another foil, makes its way fo flowly as in England. The retardation which it meets with is great in the country at large, but increases, in a vaft proportion, when it approaches either of the foci in which the learning and fcience of the nation are fuppofed to be concentrated, and when it has to penetrate through the ftrong barrier of forms, rules and opinions, by which the wifdom of our ancestors has fecured the tranquillity of the academic groves. Were it not fo, is it poflible that one of the moft fcientific men in the moft fcientific univerfity of England, when profeffedly examining the systems that have been imagined to explain the phenomena of gravitation, fhould be found hardly acquainted with the most remarkable of them, and fhould mistake the name of its author! The fyftem we fpeak of has been for a long time in the poffeffion of the public. The Essai de Chimie Méchanique, which contained the firft fketch of it, appeared fo long ago as 1758. It is true, that only few copies were printed, fo that the work was not much diffufed; but an account of it was published in the literary journals of 1762. The fame theory was more fully developed in a curious memoir, entitled Lucrece Neutonien, inferted in the Berlin Memoirs for 1782; fo that we may fairly fay, that, for more than twenty-five years, it has been, if not in the hands, at least in

a

the

the libraries of all the learned focieties in Europe; and that, to the curious in matters of this fort, it might have been known twenty years earlier. An account of it, with a biographical sketch of the author by M. PREVOST of the univerfity of Geneva, made its appearance in 1865. It feems, for all this, to be still little known; and we shall therefore take the liberty of stating a short outline of it, as of the most curious and plaufible attempt that has yet been made to account for gravity on principles purely mechanical. In this, we fhall follow M. Prevoft in a note which he has annexed to the life of the author.

Imagine, that through all space numberless corpufcles or atoms, almost infinitely fmall, are in perpetual motion: that every corpufcle has its determined direction, and moves for ever in a straight line, with a velocity far exceeding that of light. It is evident that the directions of thefe corpufcles may be fo various, they may be themselves fo small, and their velocity fo great, that though they follow one another at vaft diftances, and leave fpace, in reality, almost empty, yet may they abound every where in such a manner, that, in a portion of time almost infinitely small, a great number of them fhall pafs through every point of fpace whatfoever. On whatever point of space, therefore, our attention is fixed, we may confider it as a centre, to which the motions of an infinite number of atoms are referred, either diverging from it, or converging to it.

This conftitution of what LE SAGE calls the gravific fluid, being conceived, fuppofe a folid body to be plunged into it, of any figure whatsoever larger than one of the corpufcles, and, in fome degree, if not wholly, impervious to thofe corpufcles. This body will remain at reft, or at least without any progreffive motion, the impulfes from the corpufcles that ftrike against it being equal in oppofite directions. It may ofcillate a little backward and forward, but will not be forced from its place.

Now, let there be plunged into the gravific fluid another body, of any figure, and at any diftance from the firft. These two bodies will immediately begin to move toward one another. For the one ferving to protect the other from a certain quantity of the impulfion of the corpufcles, the currents thus left without opposition neceffarily produce their effect, and impel the bodies toward one another. Their motion toward one another will be continually accelerated; and the force producing that acceleration will increase, in proportion as the one body ftops more of the currents from falling on the other; that is, nearly as the fquares of the distances diminish.

Again, if the folid particles of which the bodies are made up, be impenetrable to the gravific corpufcles, but the bodies them

VOL. XIII. NO. 25.

H

felves,

felves, on account of their porofity permeable by them, in a certain degree, the number of corpufcles that are ftopped by each of the bodies will be, cæteris paribus, proportional to the number of folid particles, that is, to the quantities of matter in the bodies; and hence, in general, the force urging the bodies toward one another will be directly as their maffes, and inverfely as the fquares of their diftances. Thus, by mechanical action, the Newtonian law of gravitation is explained in all its parts.

The eloquent and ingenious biographer of Le Sage, having fketched the outline of his fyftem nearly as has been done above, concludes with these remarks: I ftop at the foot of this majeftic edifice with a fentiment of hope: perfuaded that the labours of the founder will not be fuffered to perifh, and that men of genius will fhare with me in the admiration it has infpired. To produce that effect, however, it no doubt behoves them to con template the whole; to fee the proofs regularly deduced, and to be affured that this fyftem, even to its moft minute details, can bear the trial of calculation and experiment.'

In the mean time, and till the competent judges can decide, from perfect knowledge, and not from a flight fketch, I wish it to be remarked, that the author of this theory was a man of a found and calculating head, improved by profound and extenfive Atudy,-fkilful in geometry, and in natural philofophy; that he spent a long and laborious life in establishing, on folid foundations, the opinion he had adopted; that he anticipated objections, fought them with avidity, liftened to them with patience, and collected them with care; that he communicated his ideas to the mot diftinguifhed men of his time, and was himself experienced in the art of instruction: that, for all these reafons, he ought not to be lightly judged of, nor confounded with the ordinary makers of fyftems.

In

join with M. Prevost in his encomium on this theory, we do by no means hold it out as free from all objection. the correspondence of Le Sage with the learned men to whom he had communicated his ideas on this subject, several difficulties are started, one of which urged by Boscovich is, as appears to us, more formidable than any other. It is grounded on the vast expense of matter required to uphold the existence of the gravific fluid. No particle of that fluid returns to its place, or ever passes a second time through the same point of space. constant supply of new particles is therefore necessary, as all those that are contained within the limits of the sensible universe at any instant, must be replaced long before they have entirely escaped from it, and gone forth to traverse for ever the deserts of uninhabited extension. The imagination is terrified at this con

stant

A

stant exertion of what cannot be considered as less than creative power, employed in producing existences that, for a limited time, are to be useful, and, through all the rest of infinite duration, are to serve no purpose whatsoever! This difficulty is indeed great; and we are still brought in sight of the CAUSE to which all others are subordinate, the cause which all rational systems must acknowledge, and can only differ about the point where its immediate action begins, and beyond which secondary causes cannot be traced. It is proved, however, by this system, that the limit, beyond which second causes cannot be traced, does not lye where Mr Vince supposes; that a mechanical cause of gravity may exist, contrary to what he has asserted; and that the incomprehensible operation of divine power may be more distant, by one step at least, than he has endeavoured to demonstrate. It may therefore be distant by many such steps; and the point at which it is placed, is not yet to be considered as given in position. We are, probably, never destined to discover the limit beyond which physical knowledge cannot be extended.

In treating of the systems imagined to explain gravitation, it is somewhat surprising that our author has made no mention of that of Boscovich, which has been so much celebrated. This omission may indeed be defended, on the plea, that Boscovich does not, strictly speaking, assign the cause of gravity, but only generalizes the facts concerning the action of bodies on one another, and reduces them all to one. This may be admitted as a ground for not entering into much detail on the subject of the theory just mentioned, but not as a reason for passing it over entirely. The leading principle in Boscovich's system is, that the particles of body are not in contact; that motion from one body to another is not communicated by the actual touching of their solid parts; and that it is not to be admitted as an axiom in physics, that bodies cannot act but where they are. He argues, that it is impossible to conceive the particles of elastic fluids to be in contact with one another; and that if, in any one instance, action takes place without contact, it may do so in all cases whatever. Thus, we are led to a very different conclusion concerning material substances; and, instead of reducing attraction, and the laws by which distant bodies seem to act on one another, to impulse, we find impulse itself reduced either to attraction or repulsion. The result of all this is, to throw considerable uncertainty over all our speculations concerning the cause of gravitation, and, what is more, concerning the essence of body, and the substratum in which its properties are conceived to be united. To know the laws of the phenomena of body, is all that science has yet attain ed with certainty,--perhaps is all that it is ever destined to atH 2 tain.

tain. What lies beyond that point, may exercise the ingenuity, and amuse the fancy of speculative men; but whether it will lead to more substantial acquisitions, must be left for futurity to determine. In the mean time, the objects to be aimed at are, to leave the matter open to inquiry; to abstain from dogmatizing; and to avoid whatever can narrow the field of philosophical investigation.

ART. VIII. The Works of John Dryden, now first collected in Eighteen Volumes: Illustrated with Notes, Historical, Critical, and Explanatory ; and a Life of the Author. By Walter Scott, Esq. 8vo. London. Miller.

1808.

THAT HAT a poet should relate the life of a poet, is both a natural and pleasing species of biography. It leads one to reckon upon more of keen interest in the subject, and more delicate criticism, than we should look for in an ordinary writer. A mere narrative it is easy to give any one is competent to detail a pedigree; to fix the date of a publication; to illustrate, by a studious research into contemporary writers, those trivial occurrences of life, which a great man partakes in common with the vulgar. Something more exquisite, more inaccessible to common bookmakers, might justly be required of one, whose fame was already ripe for eminent, and perhaps we might say, kindred excellences in the same art.

Nor are

There are two sorts of biography, and two styles of annotation, one which exhibits the talents, and one which proves the laboriousness of the writer. It would be idle petulance to depreciate altogether what falls under the latter description, and to forbid that patient research to the biographer, which is imposed as a duty upon the historian. In the case of neither, can the limits between essential accuracy, and frivolous minuteness, be defined by any written canons. Though the usefulness of every literary inquiry is in fact the standard by which it must be tried, yet is it a vague and relative one. we desirous to repress (coldly prejudiced in favour of general principles of philosophy, as we may have been deemed) all indulgence of curiosity, as to the petty occurrences of past times. Literary anecdote furnishes at least a grace and ornament to society; it displays the retentiveness of memory, which, though certainly not the most excellent, is the least invidious of our faculties; and, in superior minds, is often made subservient to the powers of sagacity and combination. But it is wofully liable to degenerate