lO Wilde, Origin of Cometary Bodies and Saturn's Rings. 



member of the solar system. Halley's comet, however, is 

 considered to move in an elh'ptical orbit and has, there- 

 fore, the longest periodic time of which astronomers have 

 certain knowledge. 



As the principle of conservation holds good alike for 

 celestial and terrestrial bodies, the moving force of comets 

 will not exceed the attraction of gravitation beyond the 

 limits of the solar system, and will be much less through 

 the conversion of molar into molecular motion by friction 

 of the discrete particles of cometary matter among them- 

 selves during the act of ejection, as also from the 

 resistance of the medium through which they move in 

 their orbits, and especially near the sun. 



The principle of conservation, as will be obvious, will 

 hold equally for the comets ejected from the planets of 

 other stellar systems. Hence the absurdity of bringing 

 cometary bodies into the solar system which contains 

 within itself the power of evolving its own comets. 

 Moreover, it will be further evident that this immigration 

 notion might be extended to include the Earth and other 

 planets as bodies from other stellar systems, captured by 

 the Sun in their wanderings from outer space. 



Jupiter, with his system of satellites, is generally 

 regarded as a miniature solar system formed by the 

 successive condensations of a nebular substance surround- 

 ing the planet. The laws of attraction, moving force, and 

 Kepler's laws have the same relations among his satellites 

 as in the planetary system. The binary progression of the 

 periodic times of the three adjoining major satellites, lo, 

 Europa, and Ganymede (which are very nearly in the ratio 

 of I, 2, 4) indicates an orderly process of evolution 

 similar to that of the binary progression of the planetary 

 distances. 



