- PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. YOl 



Theoretical velocities. Actual velocities. 

 Miles per hour. Miles per hour. 



Velocity of F, a known satellite 10,036 10,056 



Add 600 + 2= 1,200 



Velocity of G, a known satellite 11,236 11,200 



Add 600 + 2= 1,200 



Velocity of H, a known satellite 12,436 12,500 



If we compare the solar and the several statellitic systems with 

 each other, we find that there are not only many points of resem- 

 blance, but also some particulars in which they are very different. 

 It would seem that the system of Jupiter, of Saturn, of Uranus, 

 and even of the Earth and her moon, were formed by the operation 

 of the same general laws of nature which presided over the for- 

 mation of the solar system. But the conditions and circumstances 

 under which those laws acted, were different and peculiar in each 

 system. After reflecting much upon the subject, I find that all the 

 essential differences among the systems can be accounted for by 

 supposing that the primitive nebulae, from which they were formed, 

 differed from each otlier in density, or in magnitude, or both. 

 Suppose two nebulas wgre at first exactly alike in every essential 

 particular, except that one was twice as dense as the other. The 

 rings formed in the more dense system would, according to theory, 

 be just as numerous, as wide, and as near to the primary as in the 

 less dense ; but being twice as dense, they would possess twice as 

 much attractive power. They would, therefore, perturb each 

 other more, and cause a greater number of rings to become aste- 

 roidal ; consequently, the intervals between the normal secondaries 

 would be greater than in a less dense system. 



Let us now compare Jupiter's statellites with those of Saturn. 

 We may fairly presume that the present relative densities of the 

 planets are a proper criterion of the relative densities of the primi- 

 tive nebulas from which they were formed. According to this 

 rule the Saturnian nebulas was the least dense. "We can, therefore, 

 understand why the statellites of Saturn are smaller, more numer- 

 ous, and nearer to the sun and each other than those of Jupiter. 

 The bright rings of Saturn have generally been regarded as anoma- 

 lous and exceptional. I suspect, however, that there are similar 

 rings in every system ; but that in Saturn's system the matter of 

 which the rings are composed has so little density, and therefore 

 presents so large a surface for the reflection of light, that w^e can 



