1706 by Wurzelbaur, who caft her thadow upon white paper. The fame appearance was obferved on holding an opaque globe in the fun, fo as to cover his whole body from the eye; for, looking at it through a fmoked glafs, the globe appeared furrounded with a light refembling that round the moon in a total eclipfe of the fun. (168.) Thus they folve the phenomenon of the ring feen round the moon by the inflection, or diffraction as they call it, of the folar rays pafling near an opaque fubftance. As for the mall ftreaks of light, fuppofed to be lightning, they explain thefe by an hypothefis concerning the cavities of the moon themfelves; which they confider as concave mirrors reflecting the light of the fun nearly to the fame point; and as thefe are continually changing their fituation with great velocity by the moon's motion from the fun, the light which any one of them fends to our eye is feen but for a moment. This, however, does not account for the flathes, if any fuch there are, feen near the centre of the difk; though it does, in fome meafure, account for thofe at the edges, but not fatisfactorily. (169.) We have already obferved, that the occultations of the fixed ftars and planets, by the moon, in general happen without any kind of refraction of their light by the lunar atinofphere. The contrary, however, has fometimes, it is faid, been obferved, and the ftars have been seen manifeftly to change their hape and colour on going behind the moon's difk; but by many this colour has been attributed rather to the different refrangibility of the rays, in the object glafs of the telefcope, than to any real variation of colour in the planets or stars from appulfe to the moon. (170.) It has been a queftion, whether the moon and other planets are inhabited? The anfwers given to it in the negative depend on the pofition, that human beings could not exist in any of the planets on account of their distance from the fun, and confequent inequality of heat to that which the inhabitants of the earth experience; and the want of an atmosphere in the moon would as effectually preclude that body from being a fit habitation for man. But in reply it is argued, and with reafon, that the fame power which could make the earth a fit habitation for the animals upon it, could alfo adapt the organs of other animals to their various fituations in the planets: and as the earth teems with life of all kinds, we may conclude, that as there is fo great analogy between it and the planets in other refpects, the fame analogy prevails with refpe&t to life and inhabitants. SECT. IV. CONJECTURES and CONCLUSIONS refpecting COMETS. they had their periodical times of appearing; that they were out of fight for a long time, while they were carried aloft at an immenfe diftance from the earth, but became vilible when they defcended into the lower regions of the air, and thus were nearer to us. (173.) ARISTOTLE afferted that the heavens were unchangeable, and not liable to generation or cur ruption. Comets, therefore, which he believed to be generated when they firft made their appear ance, and destroyed when they vanished from our fight, he maintained, could not be heavenly bodie but rather nieteors or exhalations raifed into the upper regions of the atmosphere, where they blaz ed out for a while, and difappeared when the mat. ter of which they were formed was confumed. (174) SENECA plainly intimates, that he thought them above the moon; and argues strongly againt thofe who fuppofed them to be meteors, or h other abfund opinions concerning them; declaring his belief that they were not fire fuddenly kid, but the eternal productions of nature. He ports out alfo the only way to come at a certainty ca this fubject, viz. by collecting a number of off. vations concerning their appearance, in order to difcover whether they return periodiculy or not. "For this purpofe (fays he) one age is not fuffcieat; but the time will come when the nature of comets and their magnitudes will be demonstrated, and the routes they take, fo different from the planets, explained. Pofterity will then wondr that the preceding ages fhould be ignorant of matters fo plain and eafy to be known." (175.) The prediction of Seneca seemed for a lorg time very unlikely to be fulfilled. The great a thority which Ariftotle maintained for many age determined them to be nothing but meteors c fually lighted up in the air; though they were m nifeftly at a great height, not only above the cloudy but fubject to the diurnal revolution of the earth, In the dark and fuperftitious ages, they were he to be the forerunners of every kind of calamity, and were fuppofed to have different degrees of malignity according to the fhape they allume; from whence alfo they were differently deroms nated. Thus, fome were faid to be bearded, fome hairy; fome to represent a beam, feword, or sprar; others a target, &c.; whereas modern aftron meis acknowledge only one fpecies of comets, and account for their different appearances from thir different fituations and diftances from the fun and earth. (176.) KEFLER, in other respects a very gre genius, indulged the most extravagant conjecturs not only concerning comets, but the whole fyftem of nature. The planets be imagined to be huge animals, who fwam round the fun by mears if certain fins acting upon the ethereal fluid as the of fishes do on the water: and agreeable to th notion, he imagined the coinets to be monstros and uncommon animals generated in the celeftias fpaces; and he explained how the air engendered them by an animal faculty! (177) JOHN BODIN, a learned Frenchman of the 16th century, entertained an opinion, if poffible, ftill more ridiculous. He maintained that comets "are its which having lived on the carth innumerable ages, and being at laft arrived on the confines of death, celebrated their last triumph, or are recalled to the firmament like flining ftars! This is followed by famine, plague, &c. becaufe the people deftroy the governors and chiefs who appeafe the wrath of God!" (178.) Others have denied even the exiftence of comets, and maintained that they were only falfe appearances occationed by the refraction or reflection of light. The first rational conjecture among the moderns we meet with is that of James Bernouilli, who imagined them to be the fatellites of fome very diftant planet, which was invifible to us on account of its diftance, as were alfo the fatellites, unless when in a certain part of the course. (179.) The first aftronomer who restored the comets to their true rank in the creation, was TYCHO BRAHE. Before his time feveral had been obferved with tolerable exactness by Regiomontanus, Appian, Fabricius, and others; yet they thought them below the moon. But Tycho, being provided with much better inftruments, fet himfelf with great diligence to obferve the famous comet of 1577; and from many careful obfervations deduced that it had no fenfible diurnal parallax; and therefore was not only far above the regions of our atmosphere, but much higher than the moon. But though few have come fo near the earth as to have any diurnal parallax, all of them have what may be called an annual parallax; that is, the revolution of the earth in her orbit causes their apparent motion to be very different from what it would be if viewed from the fun: and this shows them to be much nearer than the fixed ftars, which have no fuch parallax. Kepler, the difciple of Tycho, was alfo very attentive to the motion of the comets, and found that they did not move in straight lines, as had been fuppofed. He showed that their paths were concave Towards the fun, and supposed them to move in parabolic trajectories. (180.) Sir ISAAC NEWTON at last difcovered their true motion, from the obfervations he made On the great comet of 1680. This defcended almoft perpendicularly towards the fun with a prodigious velocity; afcending again with a motion retarded, as much as it had been before accelerated. It was feen in the morning by a great number of aftronomers in different parts of Europe, from the 4th to the 25th of November, in its way toward the fun; and in the evening from the 12th of December to the 9th of March following. The 11any exact obfervations made on this comet enabled Sir Ifaac Newton to determine, that they are a kind of planets, which move in very excentric ellipfes; and this opinion is now confidered as an established truth. (181.) It has been remarkable that a greater number of comets is feen in the hemifphere towards the fun than in the oppofite; the reafon of which wiil easily appear from fig. 5. Plate XV. wherein Sreprefents the fun, E the earth, A B C D the phere of the fixed ftars; and becaufe comets neither reflect light enough to be vifible, nor emit tails confpicuous enough to attract our notice, till they come within the planetary regions, ommonly a good way within the fphere of Jupi ter, let K L M N be a sphere concentric to the fun, at fuch a distance from him, that no comet can be feen by us till it come within that distance; through E draw the plane BD perpendicular to SE, which will divide the iphore K L M N into two hemifpheres, one of which, B C D, is toward the fun, the other DA B, opposite. Now it is manifeft, that the spherical portion L M N, which is in the hemifphere BCD toward the fun, is larger than the portion N K L in the hemifphere oppofite to him; and confequently a greater number of comets will appear in the hemiphere B C D than in that marked D A B. (182.) Although the orbs of all comets are very excentric ellipfes, there are vaft differences among then. Excepting Mercury, there are no great differences among the planets either as to the excentricity of their orbits, or the inclination of their planes; but the planes of fome comets are almoft perpendicular to others, and some of their ellipfes are much wider than others. The narroweft ellipfis of any comet hitherto observed was that of 1680. There is alfo a much greater inequality in the motion of the comets than of the planets; the velocity of the former being incomparably greater in their perihelion than in their aphelion; but the planets are but very little accelerated. (183.) It is now the general opinion of aftronomers, that comets are opaque bodies enlightened by the fun. Hevelius, in a large work, wherein he gives the opinions of various authors on the fubject, mentions fome who were of the fame fentiments with himself, that comets were fo far tranfparent as to let the light of the fun pafs through them, which formed their tails. Sir Ifaac Newton was of opinion, that they are quite opaque; and in confirmation of this, he obferves, that if a comet be seen in two parts of its orbit, at equal distances from the earth, but at unequal distances from the fun, it always fhines brighteft in that nearest the fun. (184) Comets are of very different MAGNITUDES, which may be conjectured from their apparent diameter and brightnefs. Thus the head of a comet, when of the fame brightnefs and apparent diameter with Saturn, may be supposed to be nearly about the fame magnitude with that planet; though this must be attended with fome uncertainty, as we know not whether the heads of comets reflect the fun's light in the fame manner the planets do. (185.) TYCHO BRAHE found the diftance of the comet of 1577 to be about 210 femidiameters of the earth, or about 840,000 miles diftant from us, its apparent diameter being feven minutes; whence he concluded, that the true diameter of the comet was to that of the earth as 3 to 14. Hevelius, from the parallax and apparent diameter of the head of the comet in 1652, computed its diameter to be to that of the earth as 52 to 100. By the fame method he found the diameter of the head of the comet of 1664 to be at one time 12 femidiameters of the earth, and at another not much more than 5: and the diameter of the nucleus of the comets of 1661 and 1665 to be only about a tenth part of that of the earth; and Cyfatus Cyfatus makes the true diameter of the comet of him by its relative lightnefs, and carry with it the 1618 to be about the fame fize (186.) But the diameter of the atmosphere is often 10 or 15 times as great as that of the nucleus, the former in the comet of 1682, was found by Flamstead to be 2' when the diameter of the nucleus was 11 or 12". The diameter of the comet of 1744, when at the diftance of the fun from us, was about 1', hence its diameter was about 3 times that of the earth, at another time the diameter of the nucleus was nearly equal to Jupiter. (187.) Some comets, however, from their apparent magnitude and distance, have been fuppofed to be much larger than the moon, or even equal in magnitude to fome of the primary planets; and fome have imagined that, by an interpofition of these bodies betwixt the earth and fun, we might account for those darkneffes which cannot be derived from any interpofition of the moon. Such are those mentioned by Herodotus, lib. 7. cap. 37. and lib. 9. cap. 70; likewife the eclipfe mentioned by Dion, which happened a little before the death of Auguftus; and it is obfervable that Seneca faw a comet that year. Some have even attempted to account in this manner for the darkness which happened at our Saviour's crucifixion; and indeed it is certain, that were a comet in its perigee to come between the earth and fun, and to be moving the fame way with the earth, it muft caufe a darkness much more intenfe, as well as of more confiderable duration, than what could take place in any lunar eclipfe. (188.) The TAILS of comets have given rife to various conjectures; though it is acknowledged by all, that they depend on the fun fome way or other, as they are always turned from him; but in what manner this is accomplished, we cannot easily determine. Appian, Tycho Brahe, and others, thought the tail was formed by the fun's rays tranfmitted through the nucleus of the comet, which they fancied transparent, and was there refracted as in a lens of glass, so as to form a beam of light behind the comet: but this cannot be the cafe, both because the figure of a comet's tail does not anfwer to fuch a refraction, and because fuch refracted light would not be feen by a spectator placed fidewife to it, unless it fell upon fome fubftance fufficiently denfe to caufe a reflection. Des Cartes and his followers were of opinion, that the tail of a comet was owing to the refraction of its head: but if this were the cafe, the planets and principal fixed stars would have tails alio; for the rays from them pafs through the fame medium as the light from the comets. (189.) Sir ISAAC NEWTON was of opinion, that the tail of a comet is a very thin vapour which the head fends out by reafon of its heat: that it afcends from the fun juft as fmoke does from the earth that as the afcent of fmoke is caused by the rarefaction of the air wherein it is entangled, caufing fuch air to afcend and carry the fmoke up with it; fo the fun's rays acting upon the coma or atmosphere of the comet, do by rarefaction and refraction heat it: that this heated atmosphere heats, and thus rarefies the ether that is involved therein; and that the fpecific gravity, with which fuch ether tends to the fun, is fo diminished by its rarefaction, that it will now afcend from reflecting particles whereof the tail is compofed. Though the immenfely large tails of fome comets fee to require a great quantity of matter to produce them, they afford no objection to this folation: for every day's experience fhows what a great quantity of fmoke is produced from a very little wood or coal; and Newton has demonftri. ted, that a cubic inch of air equally rarefied with that at the diftance of a femidiameter from the earth's furface, would fill all the planetary regi ons to the orbit of Saturn and beyond. (190.) MARIAN fuppofed the tails of the comets to be formed out of the luminous matter whereof the fun's atmosphere confifts, to extend as far as the orbit of the earth, and to furnith matter for the aurora borealis. De la Lande joins the two laft opinions together. Part of the matter which forms the tails of comets he fuppofes to arise from their own atmosphere rarefied by heat and puited forward by the force of the light ftreaming from the fun and alfo that a comet paffing through the fun's atmosphere is drenched therein, and carries away fome of it. (191.) ROWNING objects to Newton's theory, that it can hardly be supposed the thin vapour c the tail fhould go before the more folid body the comet, when its motion is fometimes fo extremely fwift, as that of fore of the comets is fad to be after the rate (as Newton calculated the motion of the comet of 1680 to be) of no less than 880,000 miles an hour. He therefore fuppos the atmosphere of the comet to extend every way round it as far as the tail reaches; and that the part of it which makes the tail is diftinguited from the reft, fo as to fall thick upon that part of the atmosphere which goes before the comet in its progrefs along its elliptic orbit. The greateft jection to this is the immenfe magnitude of the atmospheres, as it must now be supposed, to ac count for the vaft lengths of the tails of fome co. mets, which have been said to measure above to millions of miles. (192.) M. EULER thinks there is a great affinity between the tails of the comets, the zodaical light. and the aurora borealis; and that the comm caufe of them all is the action of the fun's light on the atmospheres of the comets, of the fun, and f the earth. He fuppofes, that the impulfe of the rays of light, on the atmosphere of comets, drive fome of its finer particles far beyond the limits of that atmosphere, and that this force of impulfe combined with that of gravity toward's the comet, would produce a tail, which wed always be in oppofition to the fun, if the cust did not move. But the motion of the comet i its orbit, and, about its axis, muft vary the ption and figure of the tail, giving it a curvalat and deviation from the right line joining the CGStre of the fun and comet, which deviation wil be greater as the orbit of the comet has the great curvature, and as its motion is the more rapid. The velocity of the comet in its perihelion tay be fo great that the force of the fular rays may produce a new tail bere the old one can follow. The poffibility of this was confirmed by the co met of 1744, which had feveral tails while it was in its perihelion. (193.) The (193.) The refemblance between the tails of as the diflance of the earth contains roo; which comets and the aurora borealis, which is common- is a little more than 35 times the distance of the ly confidered as an electrical phænomenon, has earth from the fun. By a like method, the aphefuggefted an opinion far from being improbable, lion diftance of the comet of 1680 comes out 138 that the tails of comets are streams of electric times the mean distance of the earth from the fun, matter. IIAMILTON, in a small treatise, intitled, fuppofing its period to be 575 years: so that this Conjectures on the Nature of the Aurora Borealis, comet, in its aphelion, goes more than 14 times and on the Tails of Comets, fuppofes that the co- the diftance from the fun that Saturn does. Euler mets are of ufe to bring back the electric fluid to computes the orbit of this comet from three of the planets, which is continually discharged from Flamftead's obfervations taken near together, comthe higher regions of their atmospheres. pared with a fourth taken at some distance from the other three; and from thence concludes the period to be a little more than 170 years. (194) The near approach of fome comets to the fun fubjects them to intenfe and inconceivable degrees of heat. Newton calculated that the heat of the comet of 1680 must have been near 2000 times as great as that of red-hot iron. The calculation is founded upon this principle, that the heat of the fun falling upon any body at different distances is reciprocally as the fquares of thofe diftances; but it may be observed, that the effect of the heat of the fun upon all bodies near our earth depends very much on the conftitution of thofe bodies, and of the air that furrounds them. (195.) Mr WHITSON, from Flamitead's meafure of its apparent diameter, concluding the nucleus of the comet to be about ten times as big as the moon, or equal to a 4th part of the earth, at tributes the univerfal deluge to the near approach thereof. His opinion was, that the earth paffing through the atmosphere of the comet, attracted therefrom great part of the water of the flood; that the nearness of the comet raised a great tide in the fubterraneous waters, fo that the outer cruft of the earth was changed from a spherical to an oval figure; that this could not be done without making fiffures and cracks in it, through which the waters forced themfelves, by the hollow of the earth being changed into a lefs capacious form; carrying along with them trees, animals, fishes, &c. the bones, fhells, and other relics, which are often found at great depths in the earth. The fame comet, he thought, would probably, coming near the earth when heated in an immenfe degree in its perihelion, be the inftrumental caufe of that great catastrophe, the general conflagration, foretold in the facred writings, and conjectured from ancient tradition. (196) The analogy difcovered by Kepler, between the periodical times of the planets and their diftances from the fun, takes place alfo in the comets. In confequence of this, the mean diflance of a comet from the fun may be found by comparing its period with the time of the earth's revolution round the fun. Thus the period of the comet that appeared in 1531, 1607, 1682, and 1759, being about 76 years, its mean diftance from the fun may be found by this proportion: As 1, the fquare of one year, the earth's periodical time, is to 4775 the fquare of 76, the comet's periodical time; fo is 1,000,000,.the cube of 100, the earth's mean diftance from the fun, to 5,776,000,000, the cube of the comet's mean diftance. The cube root of this laft number is 1794; the mean distance itself in fuch parts as the mean distance of the earth from the fun contains 100. If the perihelion diftance of the comet, 58, be taken from 3588 double the mean diftance, we fhall have the aphelion diftance, 3530, of fuch parts (197.) The period of the comet of 1744 is much longer than even that of 1680. BETTS, in attempting to compute the tranfverfe axis of its orbit, found it come out fo near infinite, that though the orbit fhowed itself in this manner to be a very long one, he found it impoffible to calculate it without fome observations made after its perihelion. Dr HALLEY, after he had finifhed his tables of comets, found fuch a fimilitude in the elements of thofe of 1531, 1607, and 1682, that he was induced to believe them to be returns of the fame comet in an elliptic orbit: but as there was fuch a difference in their periodica! times and inclinations of their orbits as feemed to make against this opinion; and as the obfervations of the first of them in 1631 by Appian, and the 2d in 1607 by Kepler, were not exact enough to determine fo nice a point when he firft published his fynopfis in 1705; he only mentioned this as a thing probable, and recommended it to pofterity to watch for an appearance of the fame in 1758. (198.) Dr HALLEY, looking over the catalogue of ancient comets, ad finding three others at equal intervals with thofe now mentioned, afterwards grew more pofitive in his opinion; and knowing a method of calculating with eafe a motion in an elliptic orbit, how excentric foever it might be, inftead of the parabolic orbit which he had given for the comet of 1682, he fet about adapting the plan of that orbit to an ellipfis of a given space and magnitude, having the fun in one of its foci, fo as to tally with the obfervations of that comet made by Fiamftead with great accuracy, by the help of a very large fextant. He likewife corrected the places of the comet of 1551 from Appian, and thofe of the comet of 1607 from Kepler and Longomontanus, by rectifying the places of the ftars they had made use of, and found thofe places agree as well with the motion in fuch an ellipfis as could be expected from the manner of obferving of thefe aftronomers, and the imperfections of their inftruments. (199.) The greatest objection to this theory was fome difference in the inclination of the orbits, and that there was above a year's difference be tween the two periods. The comet of 1531 was in its perihelion Auguft 24; that of 1607, October 16; and that of 1682, September 4: fo that the firft of these periods was more than 76, the latter not quite 75 years. To obviate this, he reminds his readers of an obfervation made by him of the periodical revolution of Saturn having at one time been about 13 days longer than at another time; occafioned, as he fuppofed, by the near approach of Saturn and Jupiter, and the mutual attraction and and gravitation of the two planets; and obferves, that in the fummer 1581, the comet in its defcent was for fome time fo near Jupiter, that its gravitation towards that planet was one goth part of its gravitation towards the fun. This he concluded, would caufe a change in the inclination of its orbit, and also in the velocity of its motion: for by continuing longer near the planet Jupiter on the fide moft remote from the fun, its velocity would be more increased by the joint forces of both thoie bodies, than it would be diminished by them acting contrarywife, when on the fide next the fun where its motion was fwifteft. The projectile motion being thus increafed, its orbit would be enlarged, and its period lengthened; fo that he thought it probable it would not return till after a longer period than 76 years, about the end of the year 1758 or beginning of 1759. fied by a telescope on account of their immenfe diftance; whence we must conclude they thine by their own light, and are therefore fo many funs; each of which we may fuppofe to be equal, if not fuperior, in luftre and magnitude to our own.They are not fuppofed to be at equal distances from us, but to be more remote in proportion to their apparent fmal!nefs. This fuppofition is neceffary to prevent any interference of their planets and thus there may be as great a distance between a ftar of the firft magnitude and one of the fecond apparently clofe to it, as between the earth and the fixed ftars first mentioned. (204.) Others object, that the disappearance of fome of the fixed ftars is a demonftration that they cannot be funs, as it would be to the higheft degree abfurd, to think that God would create a fun which might difappear of a fudden, and leave its planets and their inhabitants in endless night. But this argument will have no weight with thefe who believe in the doctrines of revelation; which affures us, that our world will come to an end and that our fun will be deprived of his light; and consequently that all the planets, which crculate around him, will be involved in darkneís. (200.) Dr HALLEY having expreffed his opinion modeftly, though clearly enough, that this comet would appear again about the end of 1758, or the beginning of the following year, DE LA LANDE alledged he must have been at a lofs to know whether the period he foretold would have been of 75 or 76 years; that he did not give a decifive prediction, as if it had been the refult of calcula-(205.) In fhort, there is nothing inconfittent tion; and that by confidering the affair in fo loofe a manner as Halley did, there was a good deal of room for objecting to his reafoning. (201.) M. DE LA LANDE is very full in his commendation of the performance of Clairault; who, he fays, not only calculated ftrictly the effect of the attraction of Jupiter in 1681 and 1683, when the comet was again near Jupiter, but did not neglect the attraction of that planet when the comet was moft diftant; that he confidered the uninterrupted attractions of Jupiter and Saturn upon the fun and upon the comet, but chiefly the attractions of Jupiter upon the fun, whereby that luminary was a little difplaced, and gave different elements to the orbit of the comet. By this method he found the comet would be in its perihelion about the middle of April; but that, on account of fome fmall quantities neceffarily neglected in the method of approximation made ufe of by him, Clairault defied to be indulged i month; and that the comet came just 30 days before the time he had fixed for its appearance. (202.) It feems evident, indeed, from the inftance just mentioned, that comets may have their motion disturbed by the planets, efpecially by the two largeft, Jupiter and Saturn. They may alfo affect one another by their mutual gravitation when out of the planetary regions; but of this we can take no account, nor can we eftimate the refiftance of the ether through which they pafs; and yet both these caufes may have fome influence on the inclination of their orbits and the length of their periods. SECT. V. CONJECTURES and CONCLUSIONS re fpecting the FIXED STARS. (203.) Aftronomers have fuppofed the innumerable multitude of fixed ftars to be fo many funs, each of which is attended by a certain number of planets or habitable worlds like our own, as well as vifited by comets. The strongest argument for this hypothefis is, that the ftars cannot be magni with either fcripture or reafon, in fuppofing, that while infinite space is univerfally filled with iliuminating funs, and circulating planets, each world, or rather each folar fyftem of worlds, has its own periods of creation, duration, and final confummation; as we are affured ours has had, and wil have. And the difcoveries of aftronomers refpecting old ftars difappearing, and new ones being obferved, are perfectly confiftent with the doctrines of creation and diffolution, which all Christians profefs to believe, with regard to our own folar fyftem and the globe we inhabit: (See a hint refpecting the creation of other worlds, under ANGELS, § 6.) They feem to afford, likewife, a pretty ftrong argument againft the theories of Dr TOULMIN and other philosophers, who picai for the eternity of the world, and of the unive ft. (206.) Some, however, have thought that the variable ftars which disappear for a time, were planets, which were only visible during fome part of their courfe. But this, their apparent immobility, notwithstanding their decrease of lustre, will not allow us to think. Some have imagined that one fide of them might be naturally mach darker than the other, and when, by the rece tion of the ftar upon its axis, the dark fide was turned towards us, the ftar became invifible, and for the fame reafon, after fome interval, retumed its former luftre. (207.) M. MAUPERTUIS is of opinion that fome stars, by their prodigious quick rotations, on thr axis, may not only affume the figures of oblate fpheroids, but that, by the great centrifugal force arifing from fuch rotations, they may become d the figures of mill-ftones, or be reduced to fat circular planes, fo thin as to be quite invifibe when their edges are turned towards us; 5 turn's ring is in fuch pofitions. But when verv excentric planets or comets go round any fat før, in orbits much inclined to its equator, the attrac tion of the planets or comets in their periheanas must alter the inclination of the axis of that منان |