M AIIS PLANETOIDS JUPITER SATURN URANUS NE PTUNE. 



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 A> Venus T 7 ff , Mars 1|, Jupiter 5]-, Saturn 9, Uranus 19, Neptune 30. 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 

 80' 



Venus 

 46' 



Mars 

 21' 



Jupiter 

 6' 



Saturn 



Uranus 



Neptune 

 60" 



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

 expressed : 



Mercury. 



Earth. 



Mars. 



Jupiter. Saturn. Uranus. Neptune. 



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 

 and Night. 

 24h 6m 



23 

 23 

 24 

 9 

 10 



21 

 56 

 30 

 56 

 30 



Mercury 



Venus 



Earth 



Mars 



Jupiter 



Saturn 



Uranus 



Neptune 



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 ^5-, Venus f, Mars , 

 Jupiter 1330, Saturn 857, Uranus 88, Neptune 107. Their apparent diameters, as seen 

 from the sun, will be, 



Mercury Venus Earth Moon Mars Jupiter Saturn Unmus Neptano 



16" 30" 17" "2 



unknown 

 unknown 



O 



- 

 1 



1 



- 11 



- 29 



- 84 



- 164 



Length of Year. 

 Years. Months. Days. 



2 



7 





 10 

 10 



O 











28 

 15 



O 

 21 

 17 















4" -6 



10" 



37" 



16" 



Their relative bulk may be brought 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. Nichol. If we conceive the sun to 

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



