240 The American Geologist. October, 1904. 
trifugal mechanism the real nature and quaHties of a cosmic 
nebula. 
When these theorists, nevertheless, claim that they can 
demonstrate the nature and centrifugal force of a real nebula 
by means of an artificial nebula, which lacks centripetal force 
and cohesive power, then we are forced to shake our heads ; the 
whole device is overwhelmingly ridiculous. 
§8. It is evident that Laplace thought of Saturn's rings 
in developing his theory about the solar system. He looked 
upon these rings as equatorial formations caused by the cen- 
trifugal force and on the way to make a moon or moons, and 
also that the already existing moons of this system had been 
formed in the same manner from rings thrown off long ago. 
He believes, thus, that the planets themselves had at some dis- 
tant time been formed from rings of a nebula ; and that Saturn 
tells, as it were, the story of the creation of the solar system. 
Since this planet played so important a part in Laplace's in- 
vestigations, as well as in the speculations of the adherents and 
defenders of his theory, it may be well to take up that matter 
in particular right here and investigate it a little closer. 
We notice, then, first of all, that no other ex])lanation of 
the origin of Saturn's rings, except the one offered by the 
nebular theory has been generally accepted. Further, that if 
some other explanation can be made acceptable, that will also 
necessitate some other explanation of the origin of Saturn's 
moons, and likewise of the planets, the result of which will be 
the overthrow of the original theory also at this point. 
If a nebula be imagined to throw off rings by virtue of the 
centrifugal force, then the breadth and thickness of the rings 
must stand in a certain relation tO' the size of the nebula. If 
we, then, think of the original nebula, we understand at once, 
that its rings must have stood in somewhat the same relation 
to it, as for example, the rings of Saturn stand to Saturn. 
What is that relation ? 
Saturn's diameter has been found to be 76,000 miles, and 
the total width of the rings together with the distances be- 
tween them, 37,000 miles. The thickness of the rings is very 
small and is supposed to lie from 50 to 100 miles. It is pos- 
sible that they are much thicker, bi^t let us say that their 
thickness is onlv fiftv miles. Now, if we divide the diameter 
