highness to make a journey into Spain, and judge for himfelf; that if he did not like the match, means might be found to break it off; and if he did, he might bring back his miftrefs with him, as his prefence would put an end to all the formalities that would otherwise retard it: That it would alfo be fuch an obligation on the lady, as fhe could never fufficiently vaJue or requite: and that as to the great affair of ftate, the restoration of the Palatinate, it was highly probable, that the king of Spain would, in return for the honour done him by the prince's perfonal interpofition, concede to what he fhould require, or at leaft, that the Infanta might be engaged to interpofe with her influence, which in fuch a fituation could scarce fail of fuccefs.

The prince, who was naturally fond of adventures, heard this difcourse with inexpreffible delight, and was tranfported with the thoughts of puting the project in execution. One difficulty, however, immediately prefented itself, which they almoft defpaired to obviate, that of obtainng the king's confent, who was very quick in difcerning obftacles and raifing objections, and very flow in removing them.

This however was attempted under the direction of the marquis, who managed the affair with the most steady refolution and refined fubtility. The prince, as had been agreed, having waited for one of those seasons in which the king was to be approached more fuccefsfully than in others, began by telling him, that he had a propofal to make, in which his happiness was moft nearly concerned, and as the doing or not doing what he defired depended folely upon his majefty's will, he intreated his promife, that he would not communicate the thing to be propofed till he had taken his own refolution upon it. This promise was granted, probably as most fuch promises are, merely from an impaent curiofity to know what would

be revealed upon no other condition, and the prince then falling upon his knees urged his fuit with the moft vehement importunity. The king, after recovering from the firft furprize, expoftulated the affair with the prince with much lefs paffion than was expected, and then looked upon the marquis as inclined to hear what he would fay. The marquis, who had ftood by all the while without speaking a word, now faid nothing to the point, whether in prudence the journey was advisable or not, but flourished on the infinite obligation his majefty would confer upon the prince by yielding to his requeft, the refufal of which would certainly make a deep impreffion upon his fpirits and peace of mind as the greatest affliction that could befal him in the world. The prince perceiving the king was moved by what the marquis had faid, immediately enlarged on the two points which he knew were of the utmost importance in the king's judgment; he said, he knew that his marriage muft immediately follow his arrival in Spain, and that his prefence would in a moment determin the restitution of the Palatinate to his brother and fifter.

By thefe difcourfes, urged with all poffible artifice and addrefs, the king was prevailed upon to promise with lefs hesitation than was natural to him, that the prince should make the journey he fo much defired. As foon as the king had confented to the journey in general terms, they told him, that the fuccefs of the enterprize depended wholly upon expedition: that if it were to be deferred till fuch a fleet and equipage fhould be got ready as would be fit for the prince of Wales, fo much time would be spent as would difappoint the principal defign of their journey; befides, that if they should fend for a pass to France the ceremonies of afking and granting it, and thofe that would necef

farily

farily attend a public paffage through that kingdom, would be other caufes of delay, neither could fuch a pafs be reasonably depended upon in point of fecurity, as it was impoffible to guefs what advantage might be taken of their journey in favour of fome mystery or intrigue of ftate; and therefore, that they had contrived an expedient by which all inconvenience and hazard would be avoided, and the undertaking executed before it could be fufpected. Their expedient was to undertake the journey with only two fervants, who fhould know nothing of it till the moment they were to depart; and thus they faid they might pafs through France, before they were miffed at Whitehall. To this propofal, wild as it was, the king alfo gave a general confent; and the nomination of perfons to attend them and the time of their departure was deferred to the next day.

well from the nature of the journey
as from particular malice, jealoufy,
or machinations of ftate; that he
fhould lofe his credit with foreign
ftates, and the affections of his peo-
ple at home
that the marquis

would alfo be inevitably ruined by
the effect of his council, as he was
already extreamly unpopular, and
had many enemies at court, who
might make fuch ufe of this mif
conduct, that it might not be in
his power to protect him. This ex-
poftulation was interrupted by ano-
ther agony of grief, and he could
only conjure in them imperfect words
and with much diforder and many
tears, to relinquish their purpose.
[To be continued.]

HALLEY and NEWTON on the return
and effects of Comets.

SIR,

Comets having of late been a prevailing

But the king who had been fur- topic of most private as well as public prized by artifice, and overborn by converfations and fo many idle conjectures importunity, having firft made a baving been thrown out, either by foolish promife from which he might well fear or pious fraud, concerning the impend conclude the impractability of fulfilling confequences of that foretold by Dr, ing it, would abfolve him, and af- Halley to return about the year 1758, Į terwards confented to an expedient, bave thought it expedient for the quieting against which, on the fudden, he of uneafy minds, to colled from the writcould not object, without impeach- ings of thofe most excellent aftronomers, ing the prudence of his first concef- Dr. Halley and Sir Ifaac Newton, ruhatfion, was no fooner retired to his aver relates to the periodic return of comets clofet, and began to reflect on what and their near appulfe to the earth; that had paffed, than innumerable diffi- being all exhibited at one view, it may be culties and dangers crowded his more generally known. imagination; and his trouble, anxieYours &c. ty, and diftrefs, increased almost to

CANDIDUS.

R. Halley, in the edition of aftronomy of comets, fays, There are many things which make me believe that the comet which Apian • obferved in the year 1531, was the fame with that which Kepler and Longomontanus more accurate→ ly described in the year 1607, and which I myself have feen return and obferved in 1682. All the elements agree, and nothing feem

to

to contradict this my opinion, be- "tail as was feen in that of 1680-81.

fides the inequality of the periodical revolutions, which inequality is not fo great neither, as that it may not be owing to phyfical caufes. For the motion of Saturn is fo difturbed by the reft of the planets, especially Jupiter, that the periodic time of that planet is uncertain for fome whole days together. How much more therefore will a comet be fubject to fuch like errors, which rifes almott four times higher than Saturn, and whofe velocity, tho' increafed but < a very little, would be fufficient to change its orbit from an elliptical to a parabolical one. And I 4 am the more confirmed in my opinion of its being the fame, for that in the year 1456, in the • fummer time, a comet was feen paffing retrograde between the earth and the fun, much after the fame manner, which though nobody made obfervations upon it, yet from its period and the manner of its tranfit, I cannot think different from thofe I have just now mentioned. And fince, looking over the hiftories of comets, • I find, at an equal interval of time, a comet to have been feen • about Easter in the year 1305, which is another double period of 151 years before the former; hence, I think, I may venture to foretell, that it will return again in the year 1758. And if it should then fo return, we have no reafon to doubt but the reft may return • alío."

6

And again, in the confulate of Lompadius and Oreftes, about the year of Chrift 531. Such another comet appeared in the weft, of which Malela, perhaps an eye ‹ witness, relates that it was

<

a great and fearful star; that appeared in the weft, and emitted upwards from it a long white beam, and was feen for twenty days. It were to be wifhed that hilotians had told us what time of the year it was feen; but 'tis however plain that the interval between this and that of 1106, is nearly equal to that between 1106 and 1680-81, to wit, about 575 years. And if we reckon backwards fuch another period, we fhall come to the 44th year be fore Chrift, in which Julius Cæfar was murdered, and in which there appeared a very remarkable comet, mentioned by almoft all the hiftorians of those times, and by Pliny in his Natural Hiftory, lib. II. c. 24. who recites the words of Augustus Cæfar on this occafion, which leads us to the very time of its appearance, and its fituation in the heavens. In ipfis ludorum. meorum diebus, Sydus crintium per feptem dies, in regione, cali quæ fub fepten-, trionibus, eft confpecium. Id oriebatur circa undecimam horam diei, clarumque. et omuibus terris confpicuum fuit. Now thefe Luuli were dedicated Veneri generici (for from Venus the Cafars would be thought to be defcended) and began with the birthday of Auguftus, to wit, Sept. 23, and continued feven days, during which the comet appeared. Nor are we to fuppofe it was feen only thofe feven days; nor fhould we interpret the words fub feptentrionibus as if the comet had appeared in the north, but that it was feen under the Septem triones or brighter ftars of Urfa Major. And as to its rifing bora undecima diei, it can no ways be understood

• unlefs

I find, that November 11d. Th. 6 m. P. M. the comet was not above the femidiameter of the fun to the northward of the way of the earth; at which time, had the earth been there, the comet would have had a parallax equal to that of the moon, as I take it. This is spoken to aftronomers; but what might be the confequences of fo near an appulfe, or of a contact, or laftly, of a fhock of all the celeftial bodies, (which is by no means impoffible to come to pafs) I leave to be difcuffed by the ftu

unless the word diei be left out, as it is in Suetonius; for it must have been very far from the fun, either to rife at 5 in the afternoon, or at 11 at night, in which cafes it must have appeared for a long time, and its tail have been fo little remarkable, that it could by no means be called clarum et omnibus terris confpicuum fydus. But fuppofing this comet to have traced the fame path with that of the year 1680, the afcending part of the orbit will exactly reprefent all that Auguftus hath faid concerning it, and is yet an additi-dious of physical matters.' ⚫onal argument to that drawn from Dr. Halley, in the laft edition of the equality of the period. Thus his Synopfis, printed with his aftronoit is not improbable but this co- mical tables, retains most of what met may have four times vifited I have recited above, and adds what us, at intervals of about follows. 575 years whence the tranfverfe diameter of its elliptic orbit will be found 3575+575 times greater than the annual orbit; or 138 times grea-liptic orbit, however excentric, inter than the mean diftance of the ⚫ fun. One thing more; perhaps it may not be improper or pleasant to advertise the aftronomical reader, that fome of thefe ⚫ comets have their nodes so very 'near the annual orbit of the earth

un

that if it shall happen, that the earth be found in the parts of ⚫ her orbit next the node of fuch a comet, whilft the comet paffes by; as the apparent motion of the comet will be incredibly fwift, fo its parallax will become very fenfible. Now the comet of 1472 had a parallax above twenty times greater than the fun's. And if ⚫ the comet of 1618 had come down about the middle of March to his defcending node; or if that of 1684 had arrived a little fooner at its afcending node, they would have been yet much nearer the earth, and confequently have had more notable parallaxes. But hi therto none has threatened the earth with a nearer appulfe than that of 1680. For by calculation

Having fallen on a method for eafily and accurately computing the motion of a comet in an el

ftead of the parabolic orbit of the comet in 1682, as inferted in my lift of comets, I undertook fo to adapt the pofition of an elliptic one given in magnitude and fpecies with the fun in its focus, to the plane of the ecliptic, and the earth moving therein, as to reprefent the feveral exact obfervations which Mr. Flamsteed made of this comet at Greenwich, thereby fubmitting my theory to the most rigid examination.

Now it is manifeft, that this comet compleats two periods in 151 years very nearly, and thofe alternately longer and fhorter, to Takwit, of 76 and 75 years.

ing therefore 75 years for a mean period (by Prop. 15. of book I. of Sir Ifaac Newton's Principles) the greater femi-axe of its orbit will be to the fun's mean distance from the earth, as 17,8635 to 1; and the perihelial distance having been by obfervation found to be 0.5825 of fuch parts, the excentricity of the orbit comes

out

17,23810,