D. Trowbridge on the Nebular Hypothesis. 33 
partly according to the third law of Kepler; and thus the 
planets, whatever might be their distances from the sun, would 
ing some. parts without it; but it would only be slightly con- 
densed around the different bodies of the universe. 
Taste IV. 
&, <= “1308: a, 6048; 
c= 1658; ad, 22. POEs: 
ke == 2°630); a, =a ROS503 
ky == 4018; @, == 26°998; 
@,, &e., being the distances of the satellites. If we compare the 
radii of gyration, /, with the mean distance of the satellites, a, 
we see that in every instance the latter is not far from six times 
the former. If we make a similar comparison for the primary 
planets, using Table II, we see that the radius of gyration is 
only about the one-hundredth of the mean distance of the planet 
from the center of the sun. We hence conclude from this that 
to the solar spheroid. This, it would seem, is a — proof o 
the truth of the nebular hypothesis. The mass of 
imes as great as the sum of the masses of his satellites ; 
So that neglecting the masses of the satellites in comparison with 
the mass of J upiter we neglected only the small fraction so's5th. 
I supposed Jupiter homogeneous in finding his principal radius 
' gyration. : 
The periods of rotation of Uranus and of Neptune being un- 
* This conclusion differs from the basis assumed by Prof. Hinrichs in his article 
nthe Age of the Planets, this Journ., [2], xxxvii, 36-56. 
Am. Jour. Sct.—Szconp Surres, Vou. XXXIX, No. 115.—Jan., 1865, 
5 
