firft Day of January, for the prefent Year, (1758) was in 15°: 51' of Cancer, and through every Month of the Year it retrogrades, 'till the laft Day of December, it is found in 27° 30′ of Gemini; and thus, in the Space of about 18 Years, the Nodes go backward through all the Points of the Ecliptic, and confequently, once in that Time the afcending Node will be in the Beginning of Aries, and fhew the Moon nearer to, or farther from our Zenith, by 5 Degrees, than ever the Sun appears; but, when it poffeffes the autumnal Equinox, the Contrary will happen; and there are few People that live to the Age of 30 or 40 Years, but what muft remember to have feen this Variety of Lunar Altitudes, as they happen fo remarkably different, in the Space of little more than nine Years.

Euphrof. 1 fhall not trouble you with it now, Cleonicus, but, for my own Amusement at leifure Hours, I fhall put this Lunar Orbit into all its different Pofitions, with regard to the Ecliptic, to fee from thence all the Variety of Appearance that can arife, with regard to her Altitudes, Rifing, Setting, &c.

Cleon. Now you talk of her Rifing and Setting, I must obferve to you, that there will be fomething peculiarly ftrange and entertaining refult from your Experiments of that Kind; especially, if you enquire how thefe Phænomena will be circumftanced, in regard to the different Parts of the Earth, by rectifying the Globe to many different and extreme Degrees of Latitude.- -One Phanomenon of this Kind you have heard much talk of, ufually called the Harveft-Moon, and fometimes the Shepherds, and the Hunters-Moon; which, if you remember, I told you I fhould referve for an Explication, 'till I came to the Ufe of the celestial Globe; this being the only Inftrument by which it can be naturally reprefented and clearly understood.

Euphrof. Nothing will be more grateful to me, than the Explanation of a Phænomenon I have so long defired to understand, and which is looked upon almost as a Prodigy among Country People,

Cleon. As much as this has amufed and furprised many People, and as prolix and tedious as fome Difcourfes have been to explain it, you will find that there is nothing

Strange

ftrange or wonderful in the Nature of the Thing itself, and that it requires but very few Words to explain it, at leaft to the Apprehenfion of the Fair Sex.- -For

this Purpose, take your Globe, and rectify it for the Latitude of England, and turn it about, 'till the two equinoctial Points are in the Horizon, the Vernal Equinox in the Western Part, and the Autumnal Equinox in the Eaft.

Euphrof. This I have done;and what follows

then?

Cleon. You will then obferve, that the Ecliptic has a great Elevation above, or makes a very large Angle with the fouthern Part of the Horizon, viz. about 62 Degrees. Now turn the Globe about, so that the Equinoctial Points may interchangeably poffefs the fame Parts of the Horizon as before, i. e. the Autumnal Equinox in the Western Point, and the Vernal Equinox in the Eastern Point.

Euphrof. This is eafily done; and I guess what you have next to tell me.Is it not to obferve how small the Angle is which the Ecliptic now makes with the Horizon?

Cleon. That is the very Thing, my Euphrofyne; for on thefe two different Pofitions of the Ecliptic, with refpect to the Horizon, the whole Affair depends, which we fhall render more cafily to be understood, by exemplifying this Matter in the following Manner.-In the firft Cafe, fuppose there was a full Moon on the Day of the Vernal Equinox, then I bring the firft Degree of Aries to the Meridian, and fet the Hour Index at XII.— I turn the Globe, 'till that Point touches the Horizon, and fhews the Sun Setting therein;-then you will cafily understand, that the Full Moon is in the firft Point of Libra, and rifing in the Eaftern Point of the Horizon, and juft at Six o'Clock.

Euphrof. All this I perceive very plainly. What am I to obferve next?

Cleon. You will now recollect, that fince the Moon moves in one Day about 13°, therefore the next Day at Night, at Six in the Evening, the Moon will be advanced to 13° of Libra; and therefore, to fhew her Rifing in the Horizon, the Globe must be turned about, 'till that Degree of Libra appears in the Horizon;

then

then look at the Hour-Index, and you will fee it point to 16 Minutes paft VII.-Whence you obferve, the Time of her Rifing is one Hour and a Quarter later than on the Equinoctial Day, or Evening before.

Euphrof. All this is very eafy; and I prefume you are next to thew the fame Thing, or the Difference in the Time of her Rifing for the other Equinoctial Day.

Cleon. You rightly judge of my Intention.-I bring the Point of Libra, which the Sun is now fuppofed to poffefs, and place the Index to the Hour of XII.-Then turning the Globe, I bring that Point to the Western Point of the Horizon, to fhew the Sun there fetting, with the Index pointing to VI.-Then in the Eaftern Point of the Horizon, the Moon is rifing, at the fame Time, in the first Point of Aries.-Then, fince the Moon will, by Six o'Clock the next Evening, have advanced 13° forward, I must turn the Globe, till the 13° of Aries rifes ;-and I turn it, you fee, but a very little before the Moon appears; for look at the Index, and you will fee it point out the Time of her Rifing, which is but about 22 Minutes after VI.

Euphrof. The whole Thing is now unravelled-By this Experiment, I at once fee the Nature of this Phanomenon.The small Angle which the Ecliptic now makes with the Horizon, is the Reafon why fo fmall a Motion of the Globe is neceffary to make the Moon rife after the setting Sun. But 22 Minutes Difference in Time now, and 76 in the former Cafe.-Hence it is very evident, that for feveral Nights about the Autumnal Equinox, we are no fooner bereft of the Sun-Beams, but the Moon illumines the Sky with her filver Light.The contrary of all which muft happen at the Vernal Equinox, where fo large a Space must intervene between the Setting of one Luminary, and the Rifing of the other; and confequently, I am fully fatisfied from hence, why thofe lightfome, pleafant Evenings fhould occafion the forementioned Appellations of the Moon, as being fo particularly ferviceable to Shepherds, Sportsmen, and People in the Harveft-Field.And I farther obferve, that this fmall Difference of Time between the Setting of the Sun and the Rifing of the Moon, in the autumnal Season, will be ftill farther leffened, when the Nodes of the Moon

are in the Equinoctial Points, i. e. when the afcending Node poffeffes the firft Point of Aries; for then the Moon's Orbit will be moft oblique to the Horizon, or make the least Angle with it.

Cleon. Your Readinefs in apprehending the Reason of these Phænomena, fuperfedes the Neceffity of infisting any longer upon this Subject.

Your next Exercise will be the Planetary Praxis, which will afford you fuch Inftruction, as will be attended with equal Pleasure and Ufe, and be a convincing Proof, how neceffary a Part the celestial Globe must be of an Apparatus for the Education of young Gentlemen and Ladies,

The Use of the CELESTIAL GLOBE, in the Solution of PROBLEMS relating to the PLANETS and CoMETS, exemplified in that which lately appeared.

Cleonicus.

HE prefent Hour, my Euphrofyne, is deftined for your farther Inftruction in the Doctrine of practical Aftronomy. You know full well how useful the Celestial Globe is, in the Refolution of fuch Problems as relate to the Sun and Moon; and you will now find it very eafy to apply that excellent Inftrument, in the fame Manner, to folve all fuch Queftions as relate to the Planets and Comets.

Euphrof. I make no Doubt but I fhall; and it is a particular Pleasure to find, that Problems of fo fublime a Nature, admit of a Solution with fuch great Facility by the Globe. The happieft Invention fure that ever Mankind was bleft with! And it is no Wonder, when we fee those noble Inftruments in the Study of every Gentleman and Lady of Tafte.-With regard to the Planets, I prefume, there will be no great Difficulty; but how you are to inculcate the Ufe of the Globe for the Comets, I am quite at a Lofs to guefs, as I have fcarcely ever heard fuch a Thing, or ever find the Mention of it in those

2

Authors

Authors you have recommended me to read upon the Subject.

Cleon. Never fear, my Euphrofyne, though the Subject be new, it is not difficult; and you may have the Pleasure of being the firft of your Sex, to enjoy the Benefits of the Praxis on Cometary Aftronomy. The Comets are, properly speaking, no other than a very large and numerous Clafs of Planets, whose Motions, performed in the Heavens, I have already explained to you; and it is the Glory of the present Age to have the first and fulleft Confirmation of this new Species of Astronomy confirmed, as we may fay, by Experiment. I mean, by the Return of that Comet, which I formerly told you was expected, and which, during the Month of May laft, (1758) made its Appearance above our Horizon, according to the Time calculated, and predicted by the late great Dr. HALLEY.

Euphrof. The Novelty, as well as the Usefulness of fuch a Subject, muft give the highest Pleasure to every young Tyro in Aftronomy.- -The Return of a Comet has a Sound, great as the Event itself; and if I can be fo happy, as to understand by the Globe the several Appearances of fuch a wonderful Phænomenon, in its Paffage through the vifible Part of our System, it will be the Completion of my higheft Expectations. -But, I suppose you will begin with the Planets

firft.

Cleon. Yes; but that will prove a fhort and easy Task, as you have been already inftructed in the Manner of finding the Places of the Planets for any given Day in the Ephemeris; and likewife, at the fame Time, the Manner of finding their Places in the Heavens, by an artificial Planetarium, and their Pofitions and Af pects with respect to each other. The Ufe of the Globe for this Purpose is only for the Sake of Variety, and fhewing the fame Things, if poffible, in a more natural and ealy Manner.The first Thing, therefore, that I fhall enjoin you is, to take your Paper and Patches and your Ephemeris, and lay them before you on the Table by the Globe.Then find each Planet's Place feparately,

• See Dial. XIII. p. 85, 86, 87, of VOL. I. Part I.