XI. THE Aftronomers have drawn the Face of the Lecture Moon, according as it is feen with the best Telefcopes; for which we are obliged to the accurate Labours of these famous Selenographers Florentius, The SelenoLangrenus, John Hevelius of Dantzig, Grimaldus graphers or and Ricciolus, Italians; who have taken particular mers who Care to note all the fhining Parts of the Moon's bave deFace, and for the better diftinguishing them, theycribed the have given to each Part a proper Name. Lan- Surface. grenus and Ricciolus have divided the Lunar Regions among the Philofophers and Aftronomers, and other eminent Men: But Hevelius, fearing left the Philofophers fhould quarrel about the Divifion of the Lands, has fpoiled them of this their Property, and gives the Parts of the Moon thofe Geographical Names, that belong to the different Islands, Countries and Seas of our Earth, without any Regard to Situation or Figure. Aftrono Moon's LECTURE XI. Of the Obfcurations or Eclipfes of the T HERE is nothing in Aftronomy, which of the fudden Disappearings of the Sun and Moon, that is, of their Eclipfes; and the accurate Predictions when they are to come to pass, which the Aftronomers can now foretel almnft to a Minute. Tho' this be the nicest and moft fubtle Speculation of our Science, yet it is certain and undoubtable, than which nothing can Lecture can be more fublime, or worthy of our Contem XI. what. plation. THE Word Eclipfe is derived from the Greek An Eclipfe, ixxeine, which fignifies to faint, or to fwoon away: So fick and dying Perfons, when a fwooning Fit, and a death-like Faintnefs comes over them, were faid by the Greeks to fall into an Eclipfe After the fame Manner the Moon, when fhe Thines with a full Face, if the falls into the Shadow of the Earth, does lofe the enlivening Beams of the Sun's Light, and grows pale, as if she were about to die. And the Sun again, when the Moon interposes her Body, and deprives us of his Heat and Light; tho' in himfelf he retains his Luftre, yet to us he seems to vanish and grow dark. At fuch Times the Sun and Moon are faid to fuffer, and fall into an Eclipfe. Thefe Eclipses must be here explained: And, that we may begin from the first Principles; what. A Shadow, IT is to be obferved, that all opake and dark Bodies, when they are expofed to the direct Light of the Sun, caft a Shadow behind them, that is oppofite to the Line the Sun is in. This Shadow is nothing but the Lofs or Privation of Light, in the Space oppofite to the Sun, by reafon the Sun's Rays are intercepted by the opake Body. Now fince the Earth is an opake Body, it must likewise caft a Shadow towards the Space oppofite to the Sun; in which Space if the Moon fhould come, it muft neceffarily be darkened, and lofe the Light which it had before from the Sun. And because Fig. 4, 5, 6. the Figure of the Earth is Spherical, the Figure of the Shadow would be Cylindrical, if the Earth and Sun were of equal Bignefs; or if the Earth were bigger than the Sun, the Shadow would have the Figure of a Cone, which had loft a Piece at his Top or Vertex; and the farther it were extended, would grow thicker and thicker. Plate VI. The Figure of the Shadow. AND in both thefe Cafes, the Shadow would run out into infinite Space, without ever having an End And then it would involve fometimes the other Planets, Mars, Jupiter and Saturn, with |