MARS ASTEROIDS JUPITER SATURN URANUS. 97 



tude, owing to the unsteadiness of the observer's station on board a vessel ; and more 

 convenient and accurate modes have superseded it in navigation. To the inhabitants of 

 Jupiter, the opportunity will occur of witnessing upwards of four thousand lunar eclipses, 

 and as many solar, in the course of their year. To us, the planet with his moons, consti- 

 tuting what is technically called the Jovian system, exhibits a miniature picture of the 

 great solar scheme. The laws which govern the planets in their revolution round the 



sun, govern the satellites in their revolution round their centre. They move in elliptical 

 o'rbits, and, like the larger bodies, travel in a direction from west to east. Though insig- 

 nificant in point of magnitude when compared with their primary, their united bulk is 

 equal to thirteen of our moons. The first satellite will be a conspicuous object in the 

 Jovian firmament, while, to it, the great planet will be exhibited on a scale of incon- 

 ceivable magnificence, presenting every forty-two hours the varying forms of a crescent, 

 a half and full moon, and a gibbous shape, appearing a thousand times larger than our 

 moon appears to us in her corresponding phases. 



SATURN. From the noblest of the planets in point of magnitude, we pass to the most 

 extraordinary in architecture an orb which would exhibit the most fascinating appear- 

 ance to the eye but for its remoteness. An interval of space, nearly twice as great as the 

 vast chasm between Jupiter and the sun, must be crossed to arrive at Saturn, whose mean 

 distance from the solar body is about nine hundred millions of miles, and who never hails 

 the terrestrials from any station nearer than eight hundred millions. He occupies a 

 period of 10,759 solar days in accomplishing his circuit round the sun, having a mean 

 daily motion among the stars of only about 2', the thirtieth part of a degree. If observed 

 therefore entering a particular constellation of the zodiac, we may conclude that a 

 period of two years and a half will elapse before he will bid it farewell. The year of 

 the planet, extending to nearly thirty of ours, gives an age to his octogenarians, should 

 there be any, parallel to that of a terrestrial born when the Jews were in Babylon, and 

 surviving to be one of our contemporaries. His day is rather longer than that of 

 Jupiter, but shorter by more than one half than our own, as he rotates upon his axis in 

 10 h 29 m . While appearing to the naked eye as a pale feeble point in the heavens, the 

 Saturnian orb has an actual equatorial diameter of 79,160 miles, and a volume which is 

 nine hundred times greater than that of the earth. Owing to his far removal from the 

 central source of light and heat, his surface receives only the ninetieth part of these 



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