Cleon. You must know, that the apparent Path of the Comet through the Heavens is pretty nearly a great Circle of the Sphere; and therefore, as you have two Places of the Comet represented on the Globe, by the two Patches, if you bring the Centers of both thofe Patches nicely into the Horizon, you may, with a Pencil, draw a Line from one Patch to the other by the Horizon, and that will tolerably well reprefent the apparent Place of the Comet, from one Time to the other; that is, from the 31ft of March to the 6th of May.

Euphrof. This I will endeavour to do:-By raifing and depreffing the Pole, and adjusting the Patches towards the Horizon, I find the Problem not very difficult.

I have, at length, brought them nicely to coincide; one in the eastern, and the other in the western Part of the Horizon.- -From the eastern Patch, I draw a Line by the Frame of the Horizon to the western Patch, and it fhews a vaft Tract of the Heavens, through which the Comet paffed in fo fhort a Time, viz. more than 150°, which shows the Motion of the Comet to have been very quick; and I observe, it paffed through the following Conftellations in its Way, viz. by the Tail of Capricorn, the Tail of Pifcis Auftralis, by the Head of Indus, the Neck and Body of Pavo, through the Neck of Apus, below Triangulum Auftralem, above Musca, by the Lowermoft of the Crofiers, a-crofs the Hind Legs, and through the Tail of Centaurus; from thence between the two Stars in the Back of the Hydra before-mentioned; after this, it paffed on to Sextans Urania, and then to the Ecliptic, near Cor-Leonis, after which, you can better tell what became of it than myself.

Cleon. Your Performance is excellently good, my Euphrofyne. Through thofe very Conftellations, Mr. Brown obferved it to pafs from Day to Day, during the Month of April, as appears by his Letter, containing the Obfervations which he made, and are now published for the Satisfaction of the curious t.You will eafily

See the Print of the Comet's Path, taken from the Globe, in the Magazine for the Month of May, 1758.

↑ See the Beginning of the Mifcellany for the laft Month.

obferve from the Whole, that the South Latitude of the Comet being fo very great, appears now to be the Reason why we in England could not fee it in that Month; and that it was just about the Beginning of May, when it emerged again above our Horizon; after which it regaled our Eyes with a faint Appearance, 'till towards the latter End of that Month, and gradually difappeared by its diftant Recefs.- Thus much will be fufficient for giving you an Idea of the Manner, in which the various Phænomena of Comets may at any Time be reprefented on the Globe: Befides which, and the Cometarium heretofore defcribed, you may ftill receive a much clearer Infight into the Nature and Motions of a Comet, by confulting the feveral Prints which have been publifhed, with regard to the prefent Comet, and particularly that, in which the Orbit of the faid Comet is elevated, and its daily Motion marked out, together with the Ecliptic, divided into all the Months and Days of the Year, which now you are very well qualified thoroughly to understand ‡. There is yet a farther Ufe of the celeftial Globe, that will afford you fome Amusement; at leaft it will be neceffary, that a young Lady of your Tafte fhould not be unacquainted with it; I mean, the Solution of thofe Problems, which relate to the Stars, which I intend for the Improvement of the next Opportunity.

The USE of the CELESTIAL GLOBE, in the SoLUTION of PROBLEMS relative to the STARS.

I

Euphrofyne.

Cannot help thinking, whenever I caft my Eye on the Celestial Globe, but that it is an amazing Effect of Art. He muft have had a very happy Thought, who

could

The Prints, bere referred to, are a VIEW of the SOLAR SYSTEM and ORBIT of the COMET; with its proper Elevation, truly reprefenting all its Appearances for any Part of the Year:

The

could first contrive to reprefent, in fo natural a Manner, the vast expanded Canopy of the Heavens, with all its refplendent Furniture, in fo small a Compafs as the Superficies of an artificial Globe. I have but one Objection, or rather, but one Thing to remark, and that is concerning the Form of the Globe. The Surface of the Globe is convex; and that of the Heavens concave; how then can one be an adequate Reprefentation of the other?

Clean. This is very ingenioufly obferved, my Euphrofyne; but you will fee the Answer is very eafy. There is no Difference, in Reality, between the convex and the concave Surface, any more than what the Metaphyficians call Medal, and only exifts in the Form; the optical Effect of viewing any Thing, upon a convex or concave Surface, is the fame to an Eye, placed in the Center thereof: Suppofe, for Inftance, you had a Sphere of Glafs, and your Eye was placed in the Center, it would be the fame Thing, if the Stars were marked with a Diamond on the external or internal Part of the Surface, i. e. on the convex or on the concave Side; and it is the fame Thing, in regard to the artificial Globe, to an Eye on the Outside of it. For, if that Globe was to have Holes pierced through the feveral Stars, and the Globe properly rectified for a given Time, an Eye, placed in the Center, would view the Stars in the Heavens through thofe Holes respectively; each Star in the Heaven anfwering to its Reprefentative on the Globe; and therefore the Longitude, Latitude, and other Affections of the Stars, may all be determined by Means of the Apparatus to the artificial Globe, and made to correfpond exactly with what we obferved in Nature, or in the Heavens themselves.

Euphrof. You take a good deal of Pains to inform my unexperienced Judgment in Things of fo fublime a Nature:-But to come to the Point: Is there any Difficulty, arifing from any different Methods in folving Problems, relating to the Rifing, Setting, Southing, &c. of the

The Print of the Comet in the Magazine for the Month of May, 1758; and the Print, which we gave to illustrate Mr. Brown's Letter in the laft Magazine.

See alfo the large PRINT, intituled, The WONDERS of the COMETARY WORLD difplayed, c.

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Stars,

Stars, more than what you have already fhewn me, in regard to the Sun, Moon, and Planets?

Cleon. Very little, my Euphrofyne; for which Reafon we fhall foon difpatch that Affair. You have already been fufficiently taught the Doctrine of the Sphere, and the Ufe of the feveral Circles, particularly the Circles of Latitude, which belong to the Ecliptic; and therefore will here need no farther Defcriptions and, I dare say, if I require you to affign me the Latitude and Longitude, the Declination, right Afcenfion, the Time of Rifing, Southing, &c. of any particular Star, you will not need my Affiftance for that Purpofe, For Example, you may try your Skill with the Star Arcturus; one of the most remarkable Stars of the first Magnitude, in the Skirts of Böctes.

Euphrof. I am proud of the Tafk you have fet me, and will give you a Proof of my Proficiency in the best Manner I can.--The firft Thing I have to do, I am affured, muft be to rectify the Globe for this Place; and fince a Star is the Subject, and can be seen only at Night, therefore fome Hour of the Night must be fuppofed, which fhall be Ten o'Clock this very Evening.And now the Globe is rectified for that Time. And here, I fee, Bootes, with his Courfers, and confequently, that bright Star Arturus. I remember you told me, if I brought the Pole of the Ecliptic to the Meridian, and fixed the Quadrant of Altitude over it; then, if I laid the Edge of the Quadrant upon the Phenomenon, (whether the Sun or Star) it would give me the Longitude, or Place thereof in, or reduced to the Ecliptic. By doing this, I find the Longitude of Arcturus is about 20o of Libra; or 200° from the 1ft Point of Aries; and that its Latitude from the Ecliptic is about 30°.-Again, if I bring the Star to the Meridian, I obferve its Distance from the Equinoctial Line is about 20° 28', which is its Declination Northward.--At the fame Time, I obferve the Meridian to cut the 211°: 9, which is therefore the right Afcenfion of Arcturus.

:

Cleon. Admirably well, my Euphrofyne.-Now for the Time of its Rifing, Setting, and Southing, for the prefent Day, August the 9th.

Euphrof. That I will proceed to:--But first, I must

look

look for the Day of the Month on the Horizon, against which I fee 16o 30' of Leo, the Place of the Sun this Day at Noon, which Point of the Ecliptic I bring to the Meridian, and fet the Hour Hand to XII.Then I turn the Globe, 'till Ar&turus appears in the eastern Horizon, and then the Index points out the Time of his Rifing, viz. IX o'Clock this Morning.I bring this Star to the Meridian, and the Index pointing to V in the Afternoon, fhews that to be the Time of its Southing. -Laftly, I turn the Globe, 'till Arcturus is in the western Horizon, and the Index pointing to II, gives the Time of its Setting To-morrow Morning. -The Amplitude of its Rifing is near 34° to the North; and fo much is the Amplitude of his Setting of Course.

Cleon. You are fo ready in the Praxis of the Stars, that I have little more to obferve to you on that Head. It may not be amifs, however, to hint to you, that, when a Star is fituate between the Ecliptic and the Equinoctial, its Latitude may be of one Denomination, and its Declination of another; thus, for Inftance, Aldebaran in the Bull's Eye, has South Latitude and North Declination.

Another Thing I may obferve to you, and that is; there is a Sort of Poetical Aftronomy with regard to the Stars; or, there is what we call the poetical Rifing and Setting of the Stars, which was much taken Notice of by the antient Poets, Hiftorians, and Hufbandmen, (which you will readily obferve in the Writings of Hefiod, Homer, Ovid, &c.) as it was the principal Method, by which People, in that Part of the World, and in those Days, diftinguished the Changes and Diverfity of the Seafons. Of thefe Rifings and Settings, there were three Kinds, as follow. First, the Cofmical Rifing of a Star, which is, when it rifes with the Sun; but the Cofmical Setting is, when it fets at the Time the Sun rifes. Secondly, the Acronical Rifing of a Star is, when it rifes at the Time the Sun fets; and the Acronical Setting is, when it fets with the Sun. Thirdly, the Heliacal Setting of a Star is, when it approaches fo near the Sun, as to disappear in its Beams; and when it emerges from its Beams, or again becomes vifible, then it is faid to rife Heliacally.

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But