FORM OF PLANETS. 25 



This same fact is also observed in relation to other planets, 

 the outer ones, owing to the greater rapidity of their rotatory 

 motions, being much more bulged and flattened than the inner 

 ones. To the writer it is not a little surprising that this form 

 of planetary bodies has not, of itself, established among 

 astronomers the universal conviction that these bodies were 

 formed by a contraction of their materials from a previously 

 diffused state. Such, it appears, must necessarily have been 

 the case, if their superior equatorial diameter had, in its origin, 

 any connection with the centrifugal force produced by rotatory 

 motion. For if the materials of the planet, while in an 

 originally globular form, had commenced being thrown outward 

 at the equator, by the centrifugal force generated by revo- 

 lution, no known counter-force could have prevented them 

 from being all, or nearly all, thrown outward, and continually 

 farther and farther from the center, until the planet would 

 have lost its identity. Especially would this have been the 

 result, if the original velocity of revolution had continued un- 

 diminished. For it is evident that the farther a particle, or 

 collection of particles, is thrown from an axis around which 

 they, in a given period, may revolve, the greater is the centri- 

 fugal force generated by the rotation, and hence the greater 

 is its tendency to fly off still farther; while, on the other 

 hand, the farther a particle is thrown from a center of 

 attraction, the less becomes the attractive or centripetal force 

 to retain it from flying off still farther. 



The forces which produced the bulged form of planets at 

 the equator are undoubtedly the same as those which pro- 

 duced the rings of Saturn. Now, the rings of Saturn com- 

 plete a revolution in 10 hours 32 minutes and 15 seconds; 

 while the primary itself revolves in 10 hours 16 minutes and 

 1 second, or in a period of only 16 minutes and 14 seconds 



3 



