D. Trowbridge on the Nebular Hypothesis. 31 
satellites. Under certain conditions—such as Prof. Peirce 
According to this view, rings, if they exist, must be found in- 
terior to several satellites. In every case—unless changed by 
disturbing forces—the planet should rotate on its axis in less 
time than is required for any ring or satellite to revolve around 
the primary. ‘he same must hold in the case of the sun and 
he planets. 
45. When the last ring has been abandoned by any one of 
the planets, the remaining part“ must cool down and thus form 
@ primary plan The outer portions being exposed to the low 
temperature of space—at least 50° below zero Fah —they will 
ce uch more rapidly than the inner parts, and after the 
ularly the sun, (whatever might be its condition), and finally a 
balance would be reached beyond which the planet would not 
See no reason, however, to believe that any simple law regulates 
this variation of mean density from one planet to another. 
46. It would at first seem as if the satellites of the primaries 
should follow the same law of rotation that the primaries them- 
lves do; but we must recollect that the numbers representing 
the distances of the former, expressed in radii of the latter, may 
differ very considerably from the numbers representing the dis- 
tances of the latter expressed in radii of the sun. Again, the 
Tings from which the satellites were formed, were abandoned 
when the primaries were much redu in temperature, and con- 
densed, when compared with the condition of the primary rings 
© Th th i id body has abandoned all the ri 0% 
sible, or ee ees Se TE caigariively large dimensions, ae Lng 
Mass far greater t sum of the masses of all the rings separated, How 
Would the author of the meteoric theory as given in the 204th number of the North 
Ic: iew, ¢ for the fact that our Solar System is constructed upon 
this principle ? 
