G. Hinrichs on Planetology. 55 
X. The direction of rotation of the planets has been considered 
at variance with the nebular theory, ever since the discovery of 
the lunar system of Uranus. We believe that our analysis of 
this problem “ shows that the rotation of Uranus and Neptune, 
both as to position of the axis and direction of motion affords a 
very interesting confirmation of the theory. See §1, 5, 6. 
. The density of the planets has also been considered as 
being adverse to the theory; but if, as necessary, the influence 
of the age is taken into account, it is found that the minimum 
density exhibited by Saturn is demanded by the theory.” Com- 
pare § 1, 4, and § 8, 6. 
XII. The number of satellites was already shown, by Kant, to 
increase with the distance from the center of the nebula. Though 
not usually given as such, it nevertheless is a condition of sta- 
bility of the system—at any rate it is conformable to observa- 
tion ($1, 12). 
The vings of Saturn are best considered as a host of satelloids, 
corresponding to the planetoids (and meteorites) of the solar 
world—thereby accounting for the excessive thinness and the 
subdivisions of the rings.” 
In looking back upon the preceding account of the present 
aspect of the nebular theory, it will be seen ie 
A. That the four great fundamental conditions of stability re- 
ferring to the system at large are now satisfactorily deduced from 
the hypothesis of Kant-Laplace (I-IV above). 
B. That the problem of the mass (V) and the number of satel- 
lites (XII), though not completely evolved, still is sufficiently 
comprehended to enable us to say that the analytical solution is 
possible ; and 
C. That the elements referring to the single planets, or rather 
their subordinate systems, are, with the exception of the exact 
law of rotation (VII), fully deducible from the fundamental 
hypothesis of Kant and Laplace. 3 
_ We see, then, that the fundamental constants of the solar sys- 
tem, which number about seven hundred ($1), exhibit very re- 
markable mutual dependencies (§ 2), which are such as ensure 
the permanence or stability of the system (§ 3), which Newton's 
the density, rotation, and relative age of the planets; this Journal, 1864, 
xxxvii, 36, 48, 
4 33 Above, p. 49. ie 
On the density, ete.; this Journal, 1864, xxvii, 54. 
