the Earth has actually fuffered from one or many Shocks or near Paffages of Comets, before the Creation of Man? 25. IV. Whether, fetting afide any myftical and if you will truer Senfe, Mofes his own Account of the fourth Day, taken in the popular Sense, would not imply that the fixed Stars, beginning then to become vifibie to the Earth, had been really created, not only during fome Part of the Night of the Fourth natural Day, but even much longer before? Since the Rays of Light require much more than one Night's Time, to come from the fixed Stars to the Earth; and efpecially in the Newtonian System? For otherwife the Rays of Light, by which the fixed Stars, chiefly the farther moft Ones, became then visible, muft have been coming to the Earth, long before the fixed Stars themselves were created. 29. The Sun's Parallax being known, we may know nearly the real Bignefs of all the Comets whole Orbits have been or will be conftructed : And we may know it exactly, when their periodical Times are known. For we want only that the apparent Diameter of each Comet be but once [or feveral times] carefully obferved; especially in or near the Comets Perigee. Wherein Aftronomers feem to have been too negligent. 30. However, because an Example will give more Light to this Difcourfe, I fhall fhew how I calculate the Bignefs of the Comet of 1680, from what I remember I did myself obferve. Whereby it will appear, That the Diameter of that Comet was but equal to 0.06 Parts of the Diameter of the Earth. 31. Suppofing, as one may do according to my Theroy, that the Suns Parallax might be of 138 Seconds: And that the Semidiameter of the Earth was to the real Semidiameter of the Comet of 1680 as 100 to 6: Then (aying As 100 is to 6, fo are 138 Seconds to 8,325; this last Number will be the Semidiameter of the Comet feen from a Diflance equal to the Distance betwixt the Centers of the Earth and of the Sun. And again, fuppofing that the Comet, when I obferved it near its fecond Perigee, did, by a Telescope, appear no bigger than Jupiter commonly does; which was really the Cafe: At which ime I reckon that the Distance of the Comet from the Center of the Earth, was to the Distance betwixt the Centers of the Sun and of the Earth, as 53 to 100 nearly: Then faying 53 is to 100, as 8"325 to 15.1 Seconds This laft Number, as feen from the Earth, comes forth for the apparent Semidiameter of the Comet, when I faw that Comet as big as Jupiter commonly does appear. Now that very Number of Seconds 15,1 being often the mean apparent Semidiameter of Jupiter very nearly; it follows that the real Semidiameter of the Comet was but 6 Parts of the real Semidiameter of the Earth very nearly; as I had fuppofed it, after I had first feen the Refult of only two fale Suppofitions. 32. And from thence it is manifeft how exactly the real Bigness of Comets may be found out from accurate and proper Data. 33. But according to Sir Ifaac Newton, who makes the Distance of the Sun at least about 13 times greater than I do; I muft conclude that the Diameter of the Comet of 1680 would have been to the Diame to ter of the Earth, nearly as 78 to 100. Tho' according to his Conjecture p. 517, this be probably one of the smallest, or even the very fmalleft Comet of all. And in general the Danger from the Paffage, or from the Shock of Comets, becomes much greater according to him than to me. For the Diameters of Comets, as well as their Swiftness, come forth at least 13 times greater, and the Breaches, which they make in the Planes of the Orbits of the Planets, become at least 13 times longer and 13 times broader, to him, than to me; while the Bodies of the Earth and of the Moon remain the fame ; their Distance from one another changing likewise very little. 34. Sir If. Newton did admirably fhew how to determine the Orbits of But here Comets about the Sun, and their Swiftnefs in thofe Orbits. you have the frit juftifiable Eftimation of the Bignefs of a Comet; and a general Method to know quanti fint, how big they are, according to Seneca's Expreffion. I did hope that Dr Halley (who had collected all the neceffary Memoirs and Helps for determining exactly or nearly the Bignels of all the Comets, whofe apparent Diameters have been ob ferved and their Orbits described) would let the World know how great their Gobes must be, fuppofing the Sun's Parallax of what determinate Quantity he pleased. For that would be fufficient in order to know their Bignefs according to Sir Ifaac Newton's Theory; or else according t mine. In the mean while it appears by what precedes, That the Semi iameters of the Earth and of the Moon being fuppofed of 100 and of 29,57 Par s respectively, the Semidiameter of the Comet of 1680 comes forth but of 6 Parts. Tho' according to the Newtonian Syftem we might infer that the Semidiameter of that Comet was of about 78 Parts. 35. It is probable that the Danger, which the Comets expofe the Earth unto, is multiplied in Proportion to the Number of the Comets contained in the Solar Syftem. And we may tolerably conjecture their Number as follows: Tho' this, for ought I know, was never attempted before. What is certain is that the Comets, that come within reach of our Obfervations, do feem not to be much fewer than 70 or 100. 36 Their Number may be guess'd at, by the Frequency of their coming to their Perihelium; and together by a reasonable Estimation of the mean Length of their Periodical Revolutions. The 37. As to their Frequency; it appears, by Experience, that about Twelve Orbits of Comets may be observed Aftronomically in One hun dred Years; fo that thofe Orbits may be defcribed, in confequence of the Obfervations. But many Comets do pafs, either wholly unperceived; or at least not fufficiently observed by our Aftronomers. Comets, that appeared in 1607 and 1661, perform their Revolutions in 75- and in 129 Years: And they descend much lower than the Orb of Venus. Upon both which accounts, they ought to be the more eafily perceived; viz. as moving more flowly; and as receiving a greater Light from the Sun. But yet (in the Syftems of the Comets) their Revolutions in 1380 and 1456; and in 1403; are not mentioned. Other Comets, perhaps fmaller or darker, or more unconveniently placed placed, and at leaft fwifter, and more remote from the Sun, may ftil more easily pafs unobferved. Upon the whole it may be supposed thay 26 or 30 Comets may alway come in 100 Years to their Perihelion. 38. As to the mean Periodical Time of the Revolution of Comets in general; the shortest of all seems hitherto to be of 75 Years; and the longeit, of 5751. The mean Number is 325 Years. And the mean proportional is 208. But it is not impoffible that fome Comets may fpend above 600 Years in one Revolution. 39. In the following Table, to be continued as far as you please, you may chufe, at Difcretion, in the Column A, the Number by which you think you may best exprefs how many Comets come to their Perihelion in 100 Years. And in the uppermoft or lowermoft Line, you may chufe another Number expreffing the mean Number of Years that you will allow to Comets for their Revolution. And, in the Area of the Table, you will find over against those two Numbers, how many Comes there must be, in the Solar System, in confequence of your Suppofitions. For instance, If 20 (or 30) Comets do come in 100 Years to their Perihelium; And if their mean Revolution be performed in 350 Years; Then the Table gives 70 (or 10) for the whole Number of Comets. 10 10 A 100 150 200 250 300 350 100 450 500 550 600 I I II 12 12 18 141 14 21 28 35 42 49 56, 631 701 77: 84 100 150 200 250 300 350 400 450 500 550 600 40. Mercury's periodical Revolution is about 122 times fhorter than that of Saturn. But hitherto the fhorteft Period for Comets feems to be And if there be but about 8 times fhorter, than their longest Period 70 Comets in all; the mean Difference between their Revolutions seems to be but of 74 Years or thereabouts. But if there be 105 Comets; that mean Difference feems to be but of about 5 Years. 41. The Spheroids, who e longeft Axis is terminated by the Apfides, and in which the Planets and their Satellites move about their Primary Planets, do not interfect one another. So thefe Globes are in no Danger of hitting one against another, tho' they revolve nearly in the fame Plane. But it is not fo with the Comets. For inftance the Comet of 1680 is fuppofed by Sir Ifaac Newton to afcend higher than the ge nerality nerallity of Comete. And if they did revolve in the Plane of the Ecliptic, they would, most of them, in each Revolution, pafs twice thro' the Circumference of the Great Orb, and indanger greatly our lower Syftem of the Earth and of the Moon. The like may be faid of Mars, and of the other Planets and the Planes in which they revolve. Moft wifely therefore did kind Providence place the Centers of the Orbits of the Comets in great and different Latitudes; and in different Longitudes; in reference to an Eye placed in the Center of the Sun. As, on the other hand, by making fome of them Direct, and fome of them Retrogade, She does moderate and counterballance their Actions upon the Planetary Syftem, and upon one another. 42. Of the faid Comets, fome may now and then be observed from the Earth in their Tranfit under the apparent Disk of the Sun. And thefe curious Obfervations, which can be made only when the Sun fhines, might be left, with Promife of a proper Recompence, to the Care of that Multitude of Officers and Seamen unoccupied in the Royal Hofpital at Greenwich; where a fufficient Number of proper Witneffes are always at hand; and from whence Notice might be immediately given to the Royal Obfervatory. Now if there be about 100 Comets; their mean Revolution being fuppofed of 300 Years, I reckon that by a Medium, a Comet may be seen in the Disk of the Sun, once in about 800 Days. 43. How precarious then, upon the whole, confidering the intire Theory of Comets, is the State of Mankind! How dependent upon God's immediate Goodness, Forefight and Providence! And how eafly, how fuddenly and naturally, may this Globe of our Earth, and fome other Celestial Globes, with the Creatures that are in them, be made severe Examples of His Juftice; as well as the Globes of the Comets themselves! For nothing feems to hinder the Comets from beng inhabited: Since in the Perihelies of thofe that come nearest to the fun, fuch a Cloud or Chaos of mixt or even watry and incombuftible Vapours may be raised, as may obftruct wholly the Sight of the Sun; and prevent not only his vitrifying or melting, but even his heating Immoderately the Surface of the Globe. Thus, near our Tropics, the Winter or cloudy Seafan is, when the Action or Power of the Sun is Arongest there. 44. In Procefs of Time, as the Orbits and Periods of Comets may be difcovered and fettled more and more; the whole Number of obfervable Comets contained in the Solar Syftem will or may in like manner be difcovered more and more exactly: Till, after about 1500 or 2000 Years, the whole Multitude of thofe Comets, that may be easily feen from the Earth, becomes compleatly or very nearly known. Which mournful Knowledge Aftronomers have had fufficient Time to make themfelves Mafters of, but feems to be referved for Pofterity. Revifed and amended: Worcester, March 1, 1742. Nic. Facio Duillier POST-SCRIPT. I think it neceffary to add to my Discourse about Comets, a certain Criterion, by which it may commonly be known, which Comets are dark B dies like the Earth or the Moon, having no other Light but what they reflect, after having received it from the Sun: Or else which Comets may be fiery Globes, or at leaft Globes fhining by their own proper innate Light, tho' not altogether of a fiery Nature. For it is only by Ob fervations, that these different Kinds can be distinguish'd. And indeed, upon fecond thoughts, I must conclude that the Comet which appeared in 1680, did fhine by its own proper Light not borrowed from the Sun. For I have been myself a Witness, that it appeared like an entire Globe of Light, when otherwise it ought to have appeared with Phafes like Venus or the Moon. Likewife, on the 21st of March, when the Comet which has appeared this Year was feen very near the North Pole, it seemed Globular, to fome Persons who faw it from our Garden with a four Foot Telescope: And it darted its Tail, fparkling by fits like a fixed Star; as alfo Mr Doubarty Junior did obferve. From whence we may probably conclude That it was a Globe of Fire; or at least a Globe shining by its own proper Light. Worcester, April 10, 1742. Nit. Facio Duiller. On SUICIDE. From the French of M. De Voltaire. NOL. Philip Mordaunt, Coufin-Germain to the famous Earl of Peterborough, (who used to boaft he was the Man who had seen the greatest Number of Courtiers and Kings) was a young Man of Quality of about 27, well made, whofe Birth and Genius gave him room to expect the greateft Advantages. He had placed all his Happiness in a Mistress, by whom he was paffionately beloved. Yet in thefe Circumftances, he took a sudden Diftafte to Life, writ feveral Letters to bid his Friends farewel, and compos'd fome Verfes, † expreffing his Determination to die by his own Hands. Accordingly he fhot himfelf through the Head, for no other Reason, but that his Soul was tir'd of his Body; and he thought, when a Man was weary of his Lodging. it 4 was - I † I bave never been able to fee a Copy of these in English, the Meaning of the Laft "Starza run thus Opium may be ferviceable to the Wife on this Occafion; "but in my Opinion, a Brace of Balls and Refolution wil do much better." one of bis Letters be had this Expreffion. "Life has given me the Headach, and į "want a gond Church-Yard Sleep, ➡to fet me right. |