42 REVOLUTION OF THE SUN ON HIS AXIS. 



If the sun were a perfect sphere, and not sur- 

 rounded with planets, the aether would press 

 with equal force upon all parts of his surface, 

 and thus maintain him in a perfectly fixed state. 

 But as he is not a perfect sphere, and as the 

 pressure of the aether upon him from every part 

 of the solar system, is modified by all the sur- 

 rounding planets and satellites, it is obvious that 

 the centripetal force of the aether must vary on 

 different parts of his surface, so as to give him a 

 rotary motion on his axis, a result which may 

 be owing in part to certain actions going on with- 



of Galileo, that the velocity with which bodies fall to the earth is 

 the same, whether they be large or small, dense or light, when 

 the resistance of the atmosphere is removed. But if the distance 

 of planets from the sun were equal, the velocity of their satellites 

 would be in proportion to the magnitude of their primaries, and 

 inversely as the cubes of the distance. At the present distance of 

 the earth from the sun, the moon revolves around us at the rate 

 of 2,168 miles an hour, at the distance of 237,000 miles from the 

 earth. But if the earth were at the place of Jupiter, and if the 

 velocity of satellites diminish in the same ratio as that of their 

 primaries, on receding from the sun, the velocity of the moon 

 would be 2*303 times slower than at present, and only 941 miles 

 an hour. It must, however, be observed, that as the volume of 

 Jupiter is about 1.300 times that of the earth, his first satellite, 

 which is 263,111 miles from his centre, moves at the rate 

 of 37,140 miles an hour. And if his first satellite were only 

 237,000 miles from his centre, (the distance of the moon from the 

 earth,) it would move at the rate of 41,200 miles an hour, and 

 faster than the moon, (if the earth were at the place of Jupiter,) 

 in the ratio of nearly forty-four to one, a difference which must 

 therefore be owing to the difference between the magnitude of 

 Jupiter and that of the earth. 



