Page:Encyclopædia Britannica, first edition - Volume I, A-B.pdf/527

 443 A S T R C ' N O M Y. us, becomes invrfible or, account of its thinreafon to believe that the ring turns round its axis, be- ed-towards nefis as fhall be explained afterwards. The ring difapcaufe, when it is almoit edge-wife to us, it appears fbnie- pears twice in every annual revolution of Saturn, namely, what thicker on one fide of the planet than on the other ; when he is in the 19th degree both of Pifces and of Virand the thickeft edge has been feen on different fides And when Saturn is in the middle between thefe at different times. But Saturn having no vifible fpots go. on his body, whereby to determine the time of his turn- points, or in the 19th degree either of Gemini or of Saing round his axis, the-length of his days and nights, gittarius, hiS ring appears mod open to us; and then its longed 'diameter is to its (honed, as 9 to 4. and the pofition of his axis, are unknown to us. To Saturn, the fun appears only ^th part fo big as To fuch eyes as ours, unaffided by indruments, Juto us ; and the light and heat he receives from the fun piter is the only planet that can be feen from Saturn, are in the fame proportion to ours. But to compenfate and Saturn the only planet that can be feen froip Jupiter. for the fmall quantity of fun-light, he has live moons, So that the inhabitants, of thefe two planets mud either all going round him on the outfide of his ring, and near- fee much farther than we do, or have equally good inly on the fame plane with it. The firff, or neared moon druments to carry their fight to remote objefts, if they to Saturn, goes round him in r day 21 hours 19 minutes; know that there is fuch a body as our earth in the uniand is 140 thoufand miles from his centre : The fccond, verfe: For the earth is no bigger, feeu from Jupiter, than in 2 days 17 hours 40 minutes ; at the diffance of 187 his moons are feen from the earth ; and if his large body thoufand miles: The third, in 4 days 12 hours 25 mi- had not fiid attracted our fight, and .'prompted our curicnutes,. at 263 thoufand miles didance : The fourth, in fity to view him with the telefcope, we fhould never 15 days 22 hours 41 minutes, at the didance of 600 have known any thing of his moons; unlefs by chance thoufand miles : And the fifth or outermod, at one we had directed the telefcope toward that fmall part of million 800 thoufafid miles from Saturn’s centre, goes the heavens where they were at the time of obfervation. round him in 79 days 7 hours 48 minutes. Their or- And the like is true of the moons of Saturn. bits, in the fcheme of the folar fyftem, are reprefent- The orbit of Saturn is 2-J degrees inclined to the eed by the fmall five circles, marked 1, 2, 3, 4, 5, on cliptic, or orbit of our earth, and interfe&s it in the 2 id Saturn’s orbit ; but thefe, like the orbits of the other degree of Cancer and of Capricorn; fo that Saturn’s fatellites, are drawn fifty times too large in proportion to nodes are only 14 degrees from Jupiter’s. the orbits of their primary planets. The quantity of light, afforded by the fun to Jupiter, The fan Urines almod fifteen of our years together cn being but ^Tth part, and to Saturn only ^th part, of may, at fird thought, induce us to be one fide of Saturn’s ring without fetting, and as long on what we enjoy, the other in its turn. So that the ring is vifible to the lieve that thefe two planets are entirely unfit for rational inhabitants of that planet for almod fifteen of ojr years, beings to dwell upon. But, that their light is not fo and as long invifible by turns, if its axis has no inclina- weak as we imagine, is evident from their brightnefs in tion to its ring: But if the axis of the planet be inclined the night-time ; and alfo from this remarkable pheno to the ring, fuppofe about 30 degrees, the ring will ap- menon, that when tl>e fun is fo much edipfed to us, as pear and difappear once every natural day to all the inha- to have only the 40th part of his difk left uncovered bv bitants within 30 degrees of the equator, on both fides, the moon, the decreafe of light is not very fenfibje; and frequently eclipfing the fun in a Saturnian day. More- jud at the end of darknefs in total ecflpfes, when his over, if Saturn’s axis be fo inclined to his ring, it is per- wedern limb begins to be vifible, and feems no bigger pendicular to his orbit; and thereby the inconvenience than a bit. of fine filver wire, every one is furprifed'at the of different feafons to that planet is avoided. For con- brightnefs wherewith that .fmall part of him fhines. The fidering the length of Saturn’s year, which is almod e- moon, when full, affords travellers light enough to keep qual to thirty of ours, what a dreadful condition mud them from midaking their way ; and yet, according to the inhabitants of his polar regions be in, if they be Dr Smith, it is equal to no more than a 90 theufandth half that time deprived of the light and heat of the fun ? part of the light of the fan : That is,, the fun’s light is■which is not their cafe alone, if the axis of the planet 90 thoufand times as drong as the light of the moon be perpendicular to the ring, for then the ring mud hide when full. Confequently, the fun gives a thoufimd the fun from vad tracks of land on each fide of the equa- times as much light to Saturn as the full moon does totor for 13 or 14 of our years together, on the fouth fide us; and above three thoufand times as much to Jupiter. and north fide by turns, as the axis inclines to or from So that thefe two planets* even without any moons,, the fun : The reverfe of which inconvenience is another would be much more enlightened than we at iird imagood prefumptive proof of the inclination of Saturn’s axis gine ; and by having fo many, they may be very comto its ring, and alfo of his axis being perpendicular to his. fortable places of refidence. Their heat; fo far as it deorbit. pends on the force of the fun’s rays* is certainly much This ring, feen from Saturn, appears like a yad lumir lefs than ours-; to which no doubt the bodies of their nous arch in the heavens, as if it did not belong to die inhabitants are as well adapted as ours, are to the feafons planet. When we fee the ring mod open, its lhadow up- we enjoy. And if we confider, that Jupiter never has on the planet is broaded ; and from that time the Ihadotr any winter, even at'his poles* which probably is alfo the grows narrower, as the ring appears to do to us; until; cafe with Saturn, the cold cannot be fo intenfe on thefe by Saturn’s annual motion, the'fun comes to the plane of two planets as is generally imagined. Befidej* there the ring, or even with its edge; which being then direil- may be fomething in their nature or foil much warmer