Nebular Theory. — Misloekles. 241 
of the i)lant ])\ the tliickncss of the riiii^s, we find tliat the latter 
is 1/1520 of tlie former, luirther. since we have founrl the 
equatorial diameter of the nehula to have been 5.528.000,000. 
miles, it follows that the rinq; (nit of which Xcptune was 
formed must have had a thickness correspondin<T^ to at least 
1/1520 of 5.528,000,000, which is 3,636,842 miles or 
about four times the diameter of the Sun. The 
breadth of Saturn's rings is 700 times their thickness, 
but since there are distances between them, let us 
subtract a s^ood round sum. so far as the nebula is concerned, 
and say that the breadth of its rings was only 100 times its 
thickness. If we then multiply 3,636,842 by 100 we get 363,- 
648.200, which indicates in miles the breadth of the ring. If 
we further multiply its breadth by its thickness and the pro- 
duct of this by 17 billion miles, which is the length of the 
Neptunean orbit, we get its contents, which amounts to more 
than 22 septillion cubic miles. Thus we find, that this ring 
would contain matter enough to form 50,000 solar system 
like ours. And still we have used very conservative figures 
and assumed its matter to be no denser than air. 
It is evident, therefore, that the planet Neptune cannot 
have been formed out of such a ring or out of a ring of sucn 
a nebula. This, then, indicates another origin of Neptune, than 
that proposed by the nebular hypothesis, and another origin of 
the other planets also. 
Thus it is plain, at this point too, that planets are not made 
of rings. Furthermore, we understand, that the rings of Sat- 
urn serve some other purpose than to make moons, and that 
these have an origin independent of that of the planets. 
This must be said in favor of Laplace, however, that if the* 
solar system had been explored to the same extent in his time 
as it is now. His theory would very likely never have appeared 
in the form in which it is here presented. But less can be said 
in favor of the modern advocates of the theory, especially after 
tfie discovery of Neptune one thousand million miles farther 
out than Uranus. John Fiske has gone even so far. that be- 
fore the moons of jNIars were discovered, he tried to explain, in 
the light of the nebular theory, why Mars had no moons. After 
the discoverv of the moons of Mars. G. H. Darwin has tried to 
