MARS ASTEROIDS JUPITER SATURN URANUS. 105 



tral orb, in rotation and orbital motion, differ in their distances, magnitudes, densities, 

 velocities, and construction. Some are more gorgeously fitted up than their companion 

 globes. The day of Mercury nestling near the sun, and that of Uranus so distant from him 

 the moonless night of Mars, and that of Saturn with his rings and satellites must 

 be widely discordant, while each planet experiences a real day and night. The arrange- 

 ments of the system do not more strongly declare the one-ness of its authorship, than 

 the boundless resources of that author. 



The relative distances of the planets from the central source of light and heat exhibit 

 great discrepancies. Taking that of the earth as 1, the proportionate distance of Mercury 

 is 1%, Venus -fa. Mars 1^, Ceres 2f, Jupiter 5^, Saturn 9^, Uranus 19. This diversity of 

 position must produce diverse physical effects ; but even to the farthest planet the Sun is 

 still a SUN, and will afford an illumination several hundred times surpassing our largest 

 supply of lunar light. The apparent diameter of the sun, as seen from the earth, is 32'. 

 As seen from the other planets, it will be, 



Mercury Venus Mars Ceres Jupiter Saturn Uranus 



80' 46' 21' 11' 6' 3' l f '3 



The comparative size of the solar orb from these several stations may be thus pictorially 

 expressed : 



Menury. 



**' Jupiter. Saturn. Vranui. 



While a motion of translation in an orbit and one of axical rotation belong to all the 

 planets, as far as observation has gone, constituting to each respectively its year, and its 

 day and night, the length of these periods widely differs, as the annexed table shows : 



Length of Day Length of Year. 



and Night. Years. Months. Days. 



Mercury - 24h 6m 2 28 



Venus - 23 21 - 7 15 



Earth 'V - 23 56 - 1 



Mars .-,-, 24 30 1 10 21 



Ceres - ,- .unknown 4 7 11 



Jupiter - 9 56 - 11 10 17 



Saturn - 10 30 - 29 O 



Uranus - urfknown -. - 84 



The planets are spheroids more or less oblate, but their magnitudes vary prodigiously. 

 Taking the earth as 1, the comparative volume of Mercury will be ^, Venus f, Mars ^, 

 Ceres T L_, Jupiter 1,300, Saturn 900, Uranus 80. Their apparent diameters, as seen from 

 the sun, will be, 



Mercury Venus Earth Moon Mars Jupiter Saturn Uranus 

 16" 30" 17'' -2 4" -6 10" 37" 16" 4" 



Their relative bulk may be brpught before the eye as they are represented on the next 

 page. 



To express the proportionate volume of the sun, a circle with nearly a diameter of one 

 foot would be required. The following illustration of the relations of the sun and his 

 attendants is taken from Sir John Herschel and Dr. Nichols. If we conceive the sun to 

 be a globe two feet in diameter, then a grain of mustard seed, at eighty -two feet distance, 



