folded up, when the stars in heaven shall fail, and the fun shall ceafe to give his light. The fuftaining hand of God is ftill neceffary, and the prefent order and harmony which he has enabled us to understand and to admire, is wholly dependent on his will, and its duration is one of the unfearchable measures of his providence. What has become of the dazzling ftar, furpaffing Venus in brightnefs, which fhone out all at once in November, 1572, and determined Tycho Brahé to become an aftronomer? He did not fee it at half an hour past five, as he was croffing fome fields in going to his laboratory; but returning about ten, he came to a crowd of country people, who were staring at fome. thing behind him. Looking round, he faw this wonderful object. It was fo bright that his staff had a fhadow. It was of a dazzling white, with a little of a bluish tinge. In this ftate it continued about three weeks, and then became yellowish and lefs brilliant. Its brilliancy diminished faft after this, and it became more ruddy, like glaring embers. Gradually fading, it was wholly invifible after fifteen months." P. 551.

A fimilar phænomenon impelled Hipparchus, not only to the study of aftronomy, but alfo to the formation of a catalogue of the ftars, that pofterity might know whether any changes happened in the heavens. Changes accordingly have been observed; for feveral ftars, not only in his catalogue, but alfo in the catalogues of Ulugh Beigh, Tycho Brahé, and even Flamstead, are not now to be seen. " They are gone," as the profeffor obferves," and have left no trace." In these facts, as well as in the most incontrovertible marks of great and general changes, exhibited by the earth and the moon,

"We fee enough," he adds, " to convince us, that the corporeal universe bears no marks of eternal duration, or of exifting as it is, by its own energy. No!-all is perishable-all requires the fuftaining hand of God, and is fubject to the unfearchable defigns of its Author and Preserver." P. 564.

As the phenomena of the tides in our ocean evidently depend on the fun and moon, the profeffor has with great propriety explained them in this divifion of his work. They cannot indeed be called aftronomical phænomena, but they are evidently effects of that great mechanical cause which keeps the earth and the moon in their respective orbits. It is impoflible, without diagrams, to give any abftract of his doctrine on this fubject, that would be intelligible; but we have never feen the Newtonian theory more perfpicuoufly detailed, nor the apparent irregularities of the tides more fatisfactorily accounted for and reconciled to the theory.

The

The following explanation of one ftriking anomaly is intelligible by itself, and will give the reader fome notion of the manner in which our author has treated this part of his fubject.

"Suppofe the earth fluid to the centre, and at reft, without any external disturbing force. The ocean will form a perfect fphere. Let the moon now act on it. The waters will gradually rife immediately under the moon, and in the oppofite part of the earth, finking all round the equator of the fpheroid. Each particle proceeds to its ultimate fituation with an accelerated motion, becaufe, till then, the disturbing force exceeds the tendency of the water to fubfide. Therefore, when the form is attained which balances thofe forces, the motion does not ftop, juft as a pendu lum does not stop when it reaches the lowest point of its arch of vibration. Suppofe that the moon ceafes to act at this inftant. The motion will still go on, and the ocean will overpass the balanced figure, but with a retarded motion, as the pendulum rifes on the other fide of the perpendicular. It will stop at a certain form, when all the former acceleration is done away by the tendency of the water to fubfide. It now begins to fubfide at the poles of the fpheroid, and to rife at the equator, and after a certain time it becomes a perfect fphere, that is, the ocean has its natural figure. But it paffes this figure as far on the other fide, and makes a flood where there was formerly an ebb; and it would now ofcillate for ever, alternately fwelling and contracting at the points of fyzigy and quadrature. If the moon do not ceafe to act, as was juft now fuppofed, there will still be ofcillations, but fomewhat different from thofe now mentioned. The middle form, on both fides of which it ofcillates in this cafe, is not the perfect fphere, but the balanced spheroid." P. 637

The author makes fome obfervations on the tides in our atmosphere, and in the planet Jupiter, and then concludes the volume with reflections on the law of gravitation, which are at once elegant, pious, and philofophical. It is well known, that the rafh hypothefis, or rather query, thrown out by Newton concerning a material caufe of gravitation, was by others adopted as a fact, and employed by one party to convert philofophy into fanatical jargon, and by another to serve as the foundation of a fyftem of atheifm. That hypothefis, however, has been long abandoned by every man who has seriously asked himself what notion be has of an ethereal or elaftic fluid; but the atheifts have not abandoned their hopeless caufe.

"Of all the marks of purpofe and wife contrivance in the folar fyftem the most confpicuous," fays Dr. R. " is the selection of a gravitation in the inverfe duplicate ratio of the distances.

Till within these few eventful years it has been the profeffed ad. miration of philofophers of all fects. Even the materialists have not always been upon their guard, nor taken care to fupprefs their wonder at the almoft eternal duration and order which it fecures to the folar fyftem. But M. de la Place annihilates at once all the wifdom of this felection by faying, that this law of gravi tation is effential to all qualities that are diffused from a centre. It is the law of action inherent in an atom of matter, in virtue of its mere existence. Therefore it is no indication of purpose, or mark of choice, or example of wisdom. It cannot be otherwife. Matter is what it is.

"M. de la Place was aware, that this affertion, fo contrary to a notion long and fondly entertained, would not be admitted without fome unwillingnefs. He therefore gives a demon,tration of his propofition. He compares the action of gravity at different diftances with the illumination of a furface placed at different dif tances from the radiant point. Thus, if light diffused from a point shine through a hole an inch fquare, and be received on a furface parallel to the hole, and twice as far from the radiant point, we know that it will illuminate a furface of four fquare inches. Therefore, fince all the light which covers these four inches came through a hole of one inch, the light in any part of the illuminated furface is four times weaker. than in the hole, where it is four times denfer. In like manner, the intenfity and efficiency of any quality diffufed from a point, and operating at twice the diftance, muft be four times lefs or weaker; and at thrice the diftance it must be nine times weaker, &c. &c.

"But there is not the leaft fhadow of proof here, nor any fimilarity on which an argument may be founded. We have no conception of any degrees or magnitude in the intenfity of any fuch quality as gravitation, attraction, or repulfion, nor any measure of them, except the very effect which we conceive them to produce. At a double diftance, gravity will generate one fourth of the velocity in the fame time. But this meafure of its strength or weakness has no connection whatever with denfity, or figured magnitude, on which connection the whole (of M. de la Place's) argument is founded. What can be meant by a double denfity of gravity? What is this denfity? It is purely a geometrical notion, and in our endeavour to conceive it with fome diftinctnefs, we find our thoughts employed upon a certain determined number of lines, fpreading every way from the radiant point. It is very true that the number of thefe lines, which will be intercepted by a given furface at twice the diftance, will be only one fourth of the number intercepted by the fame furface at the fimple distance. But I do not fee how this can apply to the inten fity of a mechanical force, unless we can confider this force as an effect, and can fhow the influence of cach line in producing the effect which we call the force, and which we confider as the caufe of the phenomenon called gravitation. But if we take this

view of it, it is no longer an example of his propofition-a force diffufed from a centre. For, in order to have the efficiency in. verfely as the fquare of the diftance, it is meafured by the number of efficient lines intercepted. Here it is plain, that the efficiency of one of these lines is held to be equal at every distance from the centre. Such incongruity is mere nonfenfe.

This is

"This conception of a bundle of lines is the fole foundation for any argument in the prefent cafe. La Place indeed tries to avoid this by a different way of expreffing his example. A certain quantity of light, fays he, goes through the hole. uniformly fpread over four times the furface, and must be four times thinner fpread. But this, befides employing a gratuitous. notion of light, which may be refufed*, involves the fame notion of difcrete numerical quantity. If light be not conceived to confist of atoms, there can be no difference of denfity; and if we confider gravity in this way, we get into the hypothefis of mechanical impulfion, and are no longer confidering gravity as a primordial force or quality.

"But this pretended demonftration is ftill more deficient in metaphyfical accuracy. The propofition to be demonftrated is, that the gravitation towards an atom of matter is (muft be) in the inverfe duplicate ratio of the diftance, in whatever point of Space the gravitating atom is placed. But if we take our proof of the ratio from the conception of thefe lines and their density, we at once admit that there are an infinity of fituations in which there is no gravitation at all, namely, in the intervals of thefe lines. The number of fituations in which the atom gravitates is a mere nothing in comparifon of thofe in which it does not. We muft either fuppofe that both the quality, and the surface influenced by it are continuous, uninterrupted, or both must be conceived as diferete numerical quantities, the quality operating along a certain number of lines, and the furface confifting of a certain number of points. We must take one of these views; for there is no other. But neither of them gives us any conception of a different energy at different distances. If the furface be continuous, and the quality every where operative, there can be no difference of effect, unless we at once admit that the energy itfelf changes with the distance. But this change can have no relation to a change of denfity, a thing altogether inconceivable in a continuous fubftance: where every place is full, there can be no (room for) more. On the other hand, if the quality be exerted only along certain lines, and the furface only contain (con tain only) a certain number of points, we can find no ground for establishing any proportion." Nay, (we add) the atom, or col lection of atoms, may be fo placed as not to gravitate at all.

* We think that it must be refufed, as inconfiftent with the phænomena of refraction and reflection.--Rev.

"The

"The fimple and true ftate of the queftion is this. Suppofe only two indivifible atoms, or two mathematical points of fuch atoms, in the univerfe. If these atoms be fupposed to attract each other, wherever they are placed, do we perceive any thing in our conception of this force, that can enable us to fay that the attraction is equal or unequal, at different differences? For my own part I know nothing. The gravitation, and its law of action, are mere phenomena, like the thing which I call matter. This is equally unknown to me. I merely obferve certain relations, which have hitherto been conftant, and I am led by the constitution of my mind to expect the continuation of thefe relations. My collection of fuch obfervations is my knowledge of its nature. This gravitation is one of them, and this is all that I know about it.

"The obferved relations may be fuch that they involve certain confequences. This, in particular, has confequences that cannot be difputed. If gravitation in the ratio of be the primordial relation of all matter, and the fource of all others, (which is a part of La Place's fyftem) it is impoffible that a particle compofed of fuch atoms can act with a force which decreases more rapidly by an increase of diftance. But there are many phenomena which indicate a much more rapid decrease of force. Simple cohefion of folid bodies is one of these. The expanfion of fome exploding compofitions fhews the fame thing. We may add, that no compofition of fuch atoms can form repelling parti cles, nor (or) give rife to many expanfive fluids, or indeed to any of the ordinary phenomena of elaftic bodies." P. 686, &c.

The importance of this reafoning will be a fufficient apology, we truft, to our readers, for the length of the extract. The tendency towards atheifm betrayed by too many philofophers of the prefent day, renders it our duty to embrace every opportunity of exhibiting true philofophy as the handmaid of religion. In this light the appears every where in the volume before us, and would doubtlefs have appeared in it in every fubfequent volume, had the excellent author lived to complete his fyftem. Of this we are indeed affured by himself. Speaking of this fubject and the dange rous tendency of La Place's doctrine, he fays,

"Nor am I (have I) yet done with it. A demonstration has been recently offered, in a work which profeffes to explain the intimate conftitution of matter, and to account for all the phenomena of the univerfe. This will come in my way when we shall be employed in confidering the force of cohefion. Till then, requiefcat in pace."

We