which Atmosphere has alfo been in fome degree taken notice of in the last total Eclipfe, May 11. 1724 and of which I have taken notice in my Account of that Eclipfe. Only we must observe, that it appears by the Phænomena, that the Moon's Atmofphere is, in proportion at least, much higher than ours, and at the fame time much rarer alfo. That the Moon has Clouds and Vapours, is evident from the foregoing Affertions, as to its Seas and Atmosphere; and is diftinctly proved by the Phænomena of the Eclipfe, 1715. in the Scheme or Account before-mentioned. Only it must thence be noted, that the rareness of its Atmosphere is fo great, that it will not fupport fuch grofs opake Maffes as our Clouds are here; but that the Vapours there rife and fall in a more easy and infenfible manner, than is the Cafe in our Earth, at leaft fince the Deluge of Noah: For I am ftill of the fame mind as to the Antedilvuian State, which I propofed in my New Theory, that the Earth's Atmosphere was at that time comparatively regular and clear, and did then resemble what we find to be the agreeable condition of the Lunar Atmosphere at this Day; I mean by the Rifing of the Vapours in the Day, and their Falling down in the Night, in the Form of a gentle Mift; without any of thofe Opake Maffes which we call Clouds; and without any of those violent Storms of Wind, Rain, Thunder, and Lightning, &c. which we, to our Sorrow, experience in our Atmosphere fince that time. That our Earth is a Moon to the Moon it felf, and that a glorious and most useful One alfo, is not only evident from the Confiderati p.246,247 See Fig. on of the Aftronomical Syftem of the Earth and Moon, but is directly visible to our felves alfo ; it being clear that that Secondary Light which we commonly fee in the dark part of its Body, for feveral Days before and after the New Moon, is no other than Light reflected to the Moon from our Earth, and thence reflected back to us again. Nor is this very furprizing neither; fince the Square of the Earth's Diameter is more than Thirteen times as great as that of the Moon; and by Confequence the Light of the Earth is at the Moon in the fame proportion greater, than that of the Moon at the Earth. Only it must be here noted, that how confiderable foever the Light of a full Moon be to us, and the Light of a full Earth to the Moon, yet that both of them are very inconfiderable, if compar'd with that of the Sun to either of them; as being cæteris paribus in the Proportion only of the Square of the Earth's Semi-diameter, to the Square of the distance between the Earth and Moon, or, which is the fame thing, as the enlightned Hemifpherical Surface of the Moon or Earth, whence the Sun's Light is reflected, to that Hemifpherical Surface whofe Radius is the distance of the Moon from the Earth, over which that reflected Light is fpread: i. e. that the Sun's whole Light is about 48000 times as great as that of a Full Moon to us; and about 3600 times as great as that of a Full Earth to the Moon. N. B. Poffibly therefore the Reason why we have never been able to procure any fenfible Heat by burning Glaffes, when expos'd to the Moon, is not from any real want of Heat in them, them, but only because thofe Glaffes have never been large enough to gather Lunar Rays fufficient for that Purpose. N. B. The other Secondary Planets, I mean thofe about Jupiter and Saturn, are too small and too remote from us, to afford us fuch Indications of their State, as we have of the State of our Secondary Planet the Moon. Nor indeed do the primary ones themselves afford us enow of them to determine in particular their own State, as to many fuch Matters. Only Jupiter affords us the Appearance of Belts, or movable Girdles, and befides them, his Satellites afford us that famous Phænomenon of the Velocity of the Rays of Light: And Saturn, befides his Five Planets, affords us fuch a Ring encompaffing his Body, as feems to be the most fingular and curious Spectacle in the whole System. Of these Three Phænomena therefore I fhall give fome farther Account, before I proceed to the Comets and fixed Stars. (12.) As to the Belts, or movable Girdles of See Fig. Jupiter, they seem to be formed by its Clouds, VIII. which appear to lie and to move regularly, parallel to its Equator, much after that manner that our Clouds do between the Tropicks; where the conftant Trade-Winds blowing ftill from East to West, must in a lefs Degree, cause our Earth's Surface to appear at a great Distance with fuch Belts alfo. Nor is it very strange, that Jupiter's Clouds lie more copiously and regularly in fuch a parallel Situation, than ours do, if we remember the vastly greater Magnitude of Jupiter, than of our Earth; and its much quicker diurnal Revolu FA tion tion at the fame Time. But as to Jupiter's, and other bright fixed Spots, compar'd with the reft of the duller Parts, I take them, as in the Moon to be Indications of the Diversity of Land and Sea in thofe Planets; although their much greater Distance from us, makes it hitherto a great deal harder to discover the fame more diftinctly. (13.) That the Rays of Light are not a meer and abfolute Inftantaneous Preffure through a Fluid, but a real Succeffion of the small Particles of Light gradually, and in a Time flowing from the Sun's Body, is proved by the Eclipfes See Fig.IX. of Jupiter's Planets. These Eclipfes ever anticipate the even Calculation, when our Eye, by the annual Motion, meets the Rays of Light reflected from them, whether at their last Egrefs from the Sun's Light into Jupiter's Shadow, or at their first Ingrefs into the fame Light afterward; and the Eclipfes ever come too flow for the fame even Calculation, when we are going from thofe Rays; and this still in that Proportion, which implies that the Rays go no lefs than 81,000.000 Miles, or from the Sun to the Earth, in half a Quarter of an Hour. (14.) That Saturn has a broad Ring about it felf, like a broad Tin Horizon about a Globe, is now well known, fince the Days of the famous Monfieur Huygens, who first discovered what it was And every body that views SaSee Fig. X. turn through a good Telescope of Ten or more Feet, may fee it very plainly at this Day. This Ring is vaftly large; and when meafur'd by the Micrometer, and compar'd with Saturn's own |