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or run over (evolvatur) as if it were a fable, without fatiguing the attention, or dwelling upon the difficulties.”

This truly great man though he wanted ftrength to withstand the temptation of becoming the founder of à fyftem, has furnished the world with arguments by which the ancient theories were overthrown, and which, in their operation, deftroyed even that upon which he himself had bestowed fo much labour. He taught men to think for themfelves, and thofe arguments which from the pen of the great Verulam not a century before had been offered without effect, were heard in a more inquiring age from the elegant and active Descartes. Gaffendi an enlightened and penetrating genius attempted to revive the doctrines of Epicurus with confiderable alterations, but he was not attended to. The multitude had followed Defcartes, and the few who think for themselves faw too far into the extenfive field of uncultivated science to think of embracing any fyftem. Britain, the firft in reftoring the empire of reafon and fimplicity to philofophy, was already in poffeffion of many of thofe enlarged minds who can withhold their affent till proof can be obtained, and attached only to truth are capable of viewing without prejudice, and relating with fidelity. Above the mean ambition of attempting to reap fame from cafual difcoveries, they met, and communicated refpectively their intentions and purfuits. The rich harvest of nature

was before them, and their labours were fo amply rewarded, that their fueceffors who inherit the advantage of their toil can fcarcely forbear to envy their fame. This can only be faid of fuch difcoveries as may in fome meafure be called accidental, but the revolution which the state of natural philofophy experienced from the exertions of Newton reflects a degree of fame on that author which all nations and men have been proud to confirm.

This philofopher poffeffed a strength of mind, which, added to his other perfections, render him without hyperbole the boat and glory of mankind. Very early in life he had mastered the circle of human learning, and added entire fciences to thofe already difcovered and perfected. The difcovery of univerfal gravity was obfcurely made for ages before his time, as we have already observed, but the greater difcovery of the laws to which the fupreme geometer has fubjected the universe was referved for him. His fkill in making experiments was not lefs to be admired than the facility with which he arranged them, fo as to mutually illuftrate each other, and point out the real theory of nature. The fcience of Dioptrics, firft fyftematized by Defcartes, took a new form from the discoveries of Newton; and the nature of light and colours, which had been the subject of endlefs difquifitions among philofophers, became one of the moft perfpicuous parts of natural knowledge. (To be continued.)

ON LIFE.

LIFE, the facred writings inform us, is but a vapour which appeareth for a little while and then vanitheth away; and fo it is proved to be daily, by the deaths of infants and young people in general: indeed, by far the greatest part of mankind die under three years of age: nafcentes morimur is a motto as often verified as the morn returns, or fable evening yields the world to night. Alas! what is the longeft life compared with eternity?

But a moment! What are threefcore years and ten, when put in competition with everlasting ages; but a fpan! yea, lefs than a fpan and nothing: yet in fo fhort a fpace how much is to be done?-What am I? Where am I going? and what will be my portion in another and eternal world? are queftions fuited to dying immortals, and fhould be matter of daily and ferious confideration.

ΤΟ

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TO THE READERS OF THE LONDON MAGAZINE.

HE following account of the discovery of the GEORGIUM SIDUS, drawn up by the gentleman who has undertaken the aftronomical department in the London Magazine, will, we doubt not, prove entertaining and inftructive to the lovers of aftronomy.

ACCOUNT OF THE NEW PLANET, DISCOVERED BY MR. HERSCHEL, OF BATH, AND BY HIM, IN COMPLIMENT TO HIS MAJESTY, CALLED THE GEORGIUM SIDUS.

MR.

R. HERSCHEL has for many years applied himself to the confracting of reflecting telescopes for his amufement, and has fucceeded fo far, that he makes them to bear magnify ing powers of an almoft incredible bignefs-not lefs than between fix and feven thousand times! The effect which thefe very large magnifying powers had on the appearance of the fixed ftars, in fhewing many to be double, triple, and even quadruple, which were before thought to be fingle stars, fuggefted to Mr. Herschel the idea of attempting to difcover the parallax of the fixed ftars by their means.

It was in purfuit of this object that Mr. Herschel was examining the fmall ftars near the feet of Gemini, on the 13th of March, 1781, between the hours of ten and eleven at night; when he took notice of one, vitibly larger than the reft: being ftruck with its uncommon magnitude, he compared it with H. Geminorum, and the fmall ftar in the quadrangle, between Auriga and Gemini, and unding it fo much larger than they, though not quite fo brilliant, began to fufpect that it was a comet. To determine this point, he examined it with different magnifying powers, from 227, the power with which he difcovered it, to 2010; and found, continually, that the diameter of the comet (as he fuppofed it to be) increafed in proportion to the power; contrary to what is univerfally known to be the cafe when different magnifying powers are applied to the fixed fars. But in order to obtain abfolute certainty in this point, he meafured its diitance from fome of the neighbouring fixed ftars, with which he compared it again a night or two afterLOND. MAG. July 1783.

wards, and then found it was changing its fituation at the rate of about 21" in an hour.

Affured of this, Mr. Herfchel wrote immediately to the Royal Society, informing them of his difcovery, that other aftronomers might join in the obfervation of it: but not mentioning, in his firft letter, that it was neceffary to ufe a very large magnifying power to diftinguish it from a fixed far, they did not immediately discover it. This point being, however, explained, the Aftronomer Royal, as well as Profeffor Hornfby of Oxford, detected it immediately; and the former, almost as foon as he faw it, declared his fufpicions (extraordinary as the cafe feemed) that it was not one of that fpecies of bodies which we ordinarily call comets, but a planet belonging to our fyftem, of the fame nature with the ret, although, on account of its finall fize and remote fituation, it had efcaped the obfervations of aftronomers to this time.

On the 1ft of April; Dr. Maskelyne wrote an account of this difcovery to the aftronomers at Paris, and other places abroad, fo that in a very little time, obfervations were made on this very extraordinary phenomenon in most parts of Europe. In France it has been. obferved very affiduously by Meff. Le Monier, De la Lande, Meifier, Méchain, D'Argelet, Lévefque, and Darquier; in Sweden by Meff. Wargentin and Profperin; by M. Bodé, at Berlin; and by Met. Reggio, the Cæfaris, and Slope, in Italy; and, doubtlefs, by many others whofe obfervations have not come to my knowledge.

Towards the latter end of May it approached fo near to the fan as to preclude all further obfervations at that

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time;

time; and, therefore, M. Lexell, who happened then to be in England, applied himfelf to compute, as well as the few obfervations of which we were then in poffeffion would admit, the elementsofits orbit, in the fame manner that the elements of the orbits of comets have been ufually computed: that is to fay, by affuming the perihelion diftance of it from the fun, and then defcribing a parabola with this focal distance, through three affigned points, or obferved places in the heavens. In the procefs of this bufinefs M. Lexell affumed, one after another, the feveral perihelion distances 6, 8, 10, 12, 14, 16, and 18 times the diftance of the fun from the earth; but he found, on comparing thefe feveral affumptions with the obfervations, that when he affumed the perihelion distance fomewhere between 14 and 18 times the diftance of the fun from the earth, the calculations agreed beft with the obfervations: it appeared, however, to him then that it was almoft indifferent what perihelion diftance he took between these two limits, as the agreement of the calculations with the obfervations was nearly the fame in every one of them; but, in fome degree, faulty in all and as it was impoffible to determine whether this difagreement arofe from the fmall errors which the obfervations were liable to, or from the affumption of a falfe hypothefis, he laid the business afide until obfervations better fuited to the purpofe could be obtained. Some, however, found that all the obfervations would agree better with calculations founded on an hypothefis nearly circular, than any other, and that the radius of this circle ought to be about 18 times that of the earth's orbit. This circumflance feemed ftrongly to favour Dr. Maikelyne's furmife, that the newly difcovered ftar was a planet, appertaining to our fyftem; and his opinion would have gained ground fafter than it did, if Mr. Her fchel's obfervations of its diameter, the very extraordinary accuracy of which he ftrongly infifted on, had not tended to prove that its motion was then almoft in a direct line towards the earth. Trials were made abroad by different perfons to determine the elements of

this planet's orbit; but every one fuppofing it a comet, and not a planet, revolving round the fun in an orbit nearly circular, the diameter of which was about 18 times that of the earth, though they reprefented fome of the obfervations well enough, yet others, made within a few days of thefe, were very far from the truth. The Prefident de Saron, indeed, fo early as the 8th of May, declared that its distance from the fun could not be lefs than 12 times that of the earth, from the obfervations which had hitherto been made to agree with any tolerable exactnefs to the computations. In the beginning of June the Abbe Bofcovich printed a very learned memoir on this fubject, in which, by a very fimple and ingenious procefs, he fhewed that there were four different parabolas which the planet might be fuppofed to move in, and yet to correfpond equally well with the obfervations that had then been made. Soon after M. de la Place gave us elements of this orbit in the Connoiffance des Temps for 1784, deduced entirely from the obfervations of M. Meffier. He made the perihelion diftance 9.4404; the time of the perihelion January 27th, 1790, at 6 h. 19' app. time, by the meridian of Paris, and its place in 28 12'30".

On the 16th of July the planet was again obferved by Profeffor Hornsby at Oxford, after its conjunction with the fun; and a day or two afterwards by the Aftronomer Royal at Greenwich. M. Meffier obferved it on the 17th, at Paris; and thefe three gentlemen continued conftantly to obferve it, when the fate of the heavens would permit them, to the time of its oppofition with the fun; which happened, according to M. de la Lande's calculations, from the obfervations of M. Méchain on the 21ft of December, at 18 h. 3', mean time at Paris: the place of the planet being then go o° 20' 15", and its geocentric latitude o° 15'6" N.

Towards the latter end of the year, Mr. Lexell having informed M. de la Lande that in England its motion was very well reprefented by a circle, fet about computing the elements of its orbit on that hypothefis. He made choice of

three

three obfervations, which appeared to him very good ones; being all confirmed by thofe which immediately preceded and followed them: the first and laft were by M. Méchain, and the fecond by M. Meffier. The firft of thefe obfervations was made the 25th of April, the fecond on the 31ft of July, and the third on the 12th of December, 1781: all before the first oppofition of the planet with the fun. From thefe obfervations M. de la Lande deduced the geocentric longitudes and latitudes of the planet; and by affuming its diftance from the fun, he calculated the parallax of the annual orbe, and from thence the heliocentric longitudes and latitudes, at the time of the first and lait obfervations: thus he obtained the motion of the planet, as feen from the fun, in 231 days, the time between the obfervations. Ufing ftill the fame distance which he had affumed for calculating the parallax of the annual orbe, by the help of Kepler's rule, he computed the time of one revolution of the planet by the fixed ftars; and thence its motion in 231 days from the mean equinox; which motion fhould be the fame as that feen from the fun, and deduced from the obfervations, fuppofing the affumed distance of the planet from the fun to be true. But as it turned out otherwife, he varied the diftance of the planet from the fun, and repeated his calculations, until the heliocentric motion, computed by this means, from the obfervations, agreed with that drawn from the interval of time and duration of a revolution, found with the fame distance. In this manner M. de la Lande found that it was neceffary to fuppofe the distance of the planet from the fun 18.931 femi-diameters of the annual orbe, and the duration of a revolution 82,37 years. He afterwards took the obfervation of the 31ft of July, between which and the first of the three there was an interval of 97,24 days; and calculated, by means of the elements deduced above, the geocentric longitude, which he found to be only 5" more than that deduced from the obfervation; a greater agreement than the obfervations require, as they can, by no means, be depended on to twice that quantity.

Finding his hypothefis to agree fo well, thus far, M. de la Lande proceeded to calculate about 30 other obfervations, made by Dr. Mafkelyne, M. Le Monier, M. Meffier, M. Méchain, M. D'Argelet, M. Levefque; and himfelf; fome before, fome in, and others after the interval of 231 days, above fpoken of; and he had the fatisfaction to find they all agreed, reafonably well, with the computations, except two which were made about the beginning of April 1781, and a few made in the courfe of last faminer. In thefe calculations, M. de la Lande fuppofed that the heliocentric longitude of the planet on the 1ft of January 1782, at noon, by the meridian of Paris, was 3s. 0° 59' 22", and its motion with refpect to the equinoxes 4° 22' 22'1 annually. He ufed the folar places of M. de la Caille.

Finding that the errors of his hypothefis amounted to 2' in July 1782, M. de la Lande fet himself to examine what alterations it would require to make the calculations agree with the obfervations made about that time, as well as with thofe made in the beginning of April 1781, and found that to do this the diftance of the planet from the fun muft be 18,893, the time of a revolution 82,12 years, the mean daily motion, from the equinoxes, 43,22, and the mean heliocentric longitude, on the 1st of January 1782, at noon, 31°1'0". But he found alfo, that if he adopted these numbers, the calculations would differ from the obfervations near a minute and half at the oppofition, in December 1781; he, therefore, concluded that these anomalies indicated an inequality in the real motion of the planet, agreeable to what is obferved in the motions of the others; but that this inequality is fo finall as to render it unneceffary, at prefent, to feek for any other orbit than a circle; and that we must not expect to discover the true quantity of the central equation without the obfervations of many years.

M. de la Lande has alfo made fome effays to difcover the place of the node, and the inclination of the orbit of this planet to the plane of the ecliptic; but D 2

the

the fmall motion in latitude renders it very difficult to determine thefe points with any tolerable certainty at prefent: the geocentric latitudes obferved on the 25th of April and the 12th of December, 1781, were 11' 36", and 14′ 54", north: which being reduced to the fun, give the heliocentric latitudes, at thefe two times, 11' 59', and 14'8"; and thefe, with the motion in longitude between the two obfervations, 2°46'3", give the planet's diance from the node, on the 25th of April, 1781, 15° 4, and of courfe the place of the node Z 12° 55'. The inclination comes out 0° 46'.

Again, the obferved geocentric latitudes on the 16th of April 1781, and on the 26th of March 1782, were 11 48", and 15'5", and the heliocentric latitudes deduced from thefe were 12' 7, and 15'10"; the difference of the obferved longitudes was 4° 7' 44"; and thefe give the place of the node 2 12° 2', and the inclination of the orbit o° 44 M. de la Lande thinks this determination rather more to be depended on than the former. According to thefe numbers the planet paffed its node about four years ago, and it will be at its greatest north latitude about the year 1798.

'M. Bode, of Berlin, who has been very affiduous in obferving this planet, published a memoir upon it in the Ephemerides Allemande, for 1784, printed in the latter end of 1781. He alfo adopts the circular hypothefis; and found, that to make the obfervations agree with the computations from it, the distance must be 18,928. He obferves afterwards, that the ftar, N°.964, in Mayer's catalogue, where the places of the ftars are adjusted to the beginning of the year 1756, was very probably the GEORGIUM SIDUS, becaufe, according to his calculations, the planet mult have been very nearly in that fituation about the year 1755 or 1756:

and, moreover, notwithstanding he had fearched very carefully for that far in the heavens he had not been able to find it. Should this fuppofition be well founded, and Mr. Mayer's original papers, where he minuted down the obfervations which he made for determining the fituations of the ftars in that catalogue be found, as it is probable they may;* thofe obfervations would be of the utmost importance in fertling the mean motion of this planet, as well as fome of the elements of its orbit.

In April, 1782, M. Rod compofed another memoir on this fubject, in which he obferves that Tycho placed a ftar of the fixth magnitude a little above

in the tail of Capricorn, which Hevelius, after the moft laborious search, could never find: he, therefore, concludes that this ftar alfo was the Georgium Sidus; more efpecially, as his calculations place it very near that fituation in the beginning of 1587.

Thefe circumftances have induced M. de la Lande to with that the small ftars which are placed in M. de la Caille's catalogue, about the equinoctial point Aries, were re-examined; as he is in poffeffion of that aftronomer's original obfervations; and, there. fore, if it should appear that any one of those stars had difappeared which he places near the fituation the planet muft have been in about the year 1761 or 1762, the time when M. de la Caille made his obfervations, there would be the greatest reason to suppose it must have been this planet. For the fame reafon, it would, perhaps, be advifeable to enquire into the fituation which this planet was in when Mr. Flamstead and Dr. Bradly made their obfervations; and whether fome one of the stars, which they have placed in that part of the heavens, may not have left it; as by this means we may, perhaps, meet with obfervations fufficient to fettle the

theory

Since this was written, I have feen a letter from M. Méchain, of the Royal Academy of Sciences, at Paris, dated June 18 h, in which he affures us thefe papers of Profeffor Mayer are found; and that it appears from thence this celebrated attronomer obferved the flar, 964 in his catalogue, but once, If he had been lucky enough to have obferved it a fecond time, he must have made the difcovery which has been referved for Mr. Herfchel. How equally, and frugally, Providence difpenfes is bounties of every kind! M. Mayer's labours and difcoveries were already fufficient to perpetuate his name; and needed not this addition to them.

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