ADG and GV A are much more unequal.-Accordingly Mr. Brown She forward moves, now paufing, fix'd appears, But we are now arrived at the pleasant Eminence which commands in fo fine a Manner, the Western Horizon. See the illuftrious Star! how bright fhe fhines in Defiance of the Twilight, which veils, as yet, the more diftant Stars from Sight. Exphrof. I fee her, exceeding bright indeed! and, if I mistake not, fhe cafts a fenfible Shadow. Cleon. She does, indeed; the Poet might well term her the leffer Moon. Next Venus, matchlefs for her brilliant Light, Yea, fo large and bright was this Planet fome Years ago, that almoft half the Nation took her for a Comet. Euphrof. They could not chufe but be notable Aftronomers that made fuch a Miftake.But, tell me, Cleonicus, is not this the Star that hath fometimes appeared in the Day-time while the Sun has fhone? Cleon. The very fame; I do affure you, my Euphrofyne, I have feen her look forth with a ferene Brightness thro' the Refulgence of Solar Light. No Stars befides their Radiance can display With Phoebus dares in Partnership to fhine. Euphrof. Well! fhe's a matchlefs Planet, certainly, and I long to have a more intimate Acquaintance with her; therefore let me view her Complection, and fee what Afpect she puts on to the Aftronomer. Cleon. That you fhall do inftantly ;--this Gate is of a convenient Height;-there, the Tube is fixed, Euphrofyne, look thro' it in that Pofition. Euphros Euphrof. What is it I fee!-not that bright, that glaring Star,-if fo, the Glafs divefts her of a'l her radiant Glory,-fhe feems a Moon in Truth;-a Moon in the first Quarter; large as the Moon to the naked Eye;-but fome-what more vivid, yet ferene; — her Horns point upwards :-But why does fhe not appear with a full Face?Is the Fault in the Glafs, or what is the Reafon? Cleon. The Glafs fhews all of her that can be seen ; the Reason why you fee only Part of her Orb enlightened is evident from the Scheme; for let us fuppofe fhe were viewed from her fuperior Conjunction at D; then, because all that Part of the Body which is turned towards the Sun is feen alfo from the Earth; fhe muft then appear wholly enlightened, and like the Moon at full. Secondly, If he were viewed in the Point A or G, then but half her enlightened Face could be seen at the Earth, and therefore she would appear as the Moon of a Quarter old. Thirdly, If we suppose her at V, in her inferior Conjunction; then all her light Part being turned to the Sun, nothing but her dark Part can be towards the Earth; and, like the New Moon, the disappears, and can't be seen, even with a Telescope, unless it be in the Face of the Sun. Fourthly, In the Points B, more than half her enlightened Disk will appear at the Earth, and in the Point C ftill more than before; therefore in thofe Places fhe will appear gibbous. Fifthly, In the Point X, between V and A or G, fhe will appear horned, like the Moon about 3 or 4 Days old; which is the prefent Cafe of this Planet. Eupbrof. But there is fomething which yet feems ftrange, and that is, Venus is now brighteft, and yet but a fmall Part of her enlightened Surface is towards us; pray, Cleonicus, as we walk home, give me to understand the Reafon thereof. Cleon. That you will eafily perceive from the Scheme; for, first, if the Planet be at D, fhe will indeed be a Full Moon; but then she will be near three times farther from the Earth T than the is now at X, and confequently, fhe will appear 7 or 8 Times lefs there (provided the E 3 could could be feen) than at X; tho' there we fee but a Quarter of her enlightened Side, yet that will appear larger and more brilliant than her whole Hemifphere at D. Again, at and about her upper Conjunction at I, fhe cannot be feen by Reafon of her Nearnefs to the Sun; but getting farther out of the Sun-Beams, fhe augments her apparent Size, and Luftre, till fhe comes near the Point. X, where it is greateft of all, as before faid, and then fhe is about 40 Degrees diftant from the Sun. Euphrof. I prefume, Cleonicus, I apprehend you full well; and thus, as the approaches to V, we gradually lofe Sight of her again. Clean. Yes, unlefs fhe fhould chance to pafs over the Sun's Difk, or Face (as I faid of Mercury) in her inferior Conjunction; and this fhe will do in the Years 1761, 1769, 2004, 2012, 2247, 2255, in Jun; and in the Years 1874, 1882, 2117, 2125, 2360, 2368, in December; at which Times fhe will appear a black, but beautiful Spot in the Sun. * Euphrof. Pray, how far is the Orbit of Venus from the Sun ? Cleon. About Fifty-nine Millions of Miles, that is, about twice as far off as Mercury; and therefore the Light and Heat, at Venus, will be but about a fourth Part of what it is at Mercury; and twice as great as ours. Euphrof. I recollect, you told me Venus fpent 225 Days in revolving annually about the Sun; but pray, Cleonicus, has the any Motion about her own Axis? Cleon. Some fay, fhe has a diurnal Motion in 23 Hours; and others affirm, it is in 24 Days and 8 Hours; a very wide Difference indeed!--Such a Motion is difcoverable only by Spots; and as I have never had it in my Power to procure a Telescope that would fhew them, I can fay but little about this Matter. Euphrof. What you now fay is very extraordinary; I fuppofe thofe Inftruments are vastly expenfive; but if they Of this curious Phænomenon we have given a much larger and more particular Account in a Treatife entituled, The ASTRONOMY and GEOGRAPHY of TRANSITS, illuftrated by thole of the Planet Venus in 1761 and 1769. they are, one would think there were People of Fortune enough to render them more common, and to oblige every curious Perfon with the Use of them upon fuch Occafions. But fay, what is the Magnitude of Venus? Cleon. She is computed to be a Globe of Seven Thoufand Nine Hundred and Six Miles in Diameter; and is therefore about 36 Times bigger than Mercury. Euphrof. Well! I think we have talked her Ladyship out of Sight; for I can fee her no where now. Cleon. She is now gone to greet the jovial Sailors on the Western Seas. For you know fhe is, and ever was, the most of any Star admired and adored both by Land and Sea; and fuch prodigious Veneration had the Ancients for her, that they made her their Favourite Goddefs, and gave her all that Deity itself could claim. Thus one of their Poets fings of her: Delight of human Kind and Gods above, For every Kind, by thy prolific Might, Springs, and beholds the Regions of the Light. For thee the Land in fragrant Flowers is drefs'd; } DRYD. LUCRET. DIALOGUE IX. Of the EARTH; confidered as a PLANET. Τ Euphrofyne. HE next Orbit to Venus in the Solar Syftem, I Tfee, is that of the Earth. Cleon. Yes; and thus Mr. Baker elegantly defcribes the Earth's Motion. E 4 More More diftant fill our Earth comes rolling on, Thus alfo Mr. Brown; UNIVERSE. Lo! in the Midft, fair Earth, our native Seat, Euphrof. At what Distance is the Earth's Orbit from the Sun ? Clean. The Earth is removed to the Distance of upwards of 90 Millions of Miles, which is fuch a convenient Situation in the Syftem, with Respect to Light and Heat, as adinits of no Excess of either. And therefore Sir R. Blackmore's religious Reflection on this Subject was very judiciously made. See! how the EARTH has gain'd that very Place, CREATION. Euphrof. In what Time does the Earth make a compleat Revolution in its Orbit? Cleon. In the Space of Three Hundred Sixty-five Days and a Quarter; which makes what we call our Solar Year. This is called the Earth's Annual Motion. Euphrof. I remember you mentioned another Motion of the Earth, which I have not yet feen in the Planetarium. Cleon. Yes, my Euphrofyne; it has another Motion about its own Axis once in 24 Hours nearly, which is the Space of a natural Day; this is called the Diurnal Motion, |