230 The American Geologist. October, 1904. 
adherents of that theory have not, however, been able to find 
any sufficient cause for the rotation of the nebula. This is 
important ; for the nebula must of necessity rotate in order to 
form and throw ofif rings. They supposed that this cause 
could not possibly be any other than the contraction of the 
nebular mass, which was taken for granted and assumed to be 
a fact. 
Herbert Spencer and John Fiske have dwelt with great de- 
light on this point and claimed that nothing can be imagined 
more clearly proven and demonstrated. They have pointed 
out, that according to the theory in question the planets Jupiter 
and Saturn must rotate very rapidly on account of their vast 
mass and powerful gravity ; and which they think the obser- 
vations prove to be true. They have pointed out further, that 
said planets must for the same reason have thrown off many 
rings, and, consequently, have many moons, which the obser- 
vations also prove to be correct. This view is, therefore, in 
the words of Herbert Spencer, incontrovertible. 
We shall now take up these premises and conclusions one 
by one and see whether we can not derive these same phe- 
nomena from other sources. Perhaps we may find some other 
methods than those mentioned above, by means of which we 
may be able to explain why the planets move in orbits analo- 
gous to the plane of the solar equator ; and likewise we may 
detect another cause for the corresponding state of things in 
regard to the moons and planets; and hence we may possibly 
discover another manner than that set forth in the nebular 
theory, in which the moons have come to the planets. 
The last mentioned of these investigations we cannot un- 
dertake immediately, however, as that would carry us too far 
from our main subject at present. Let us rather begin with 
the fundamental point in the theory, the starting point, and 
return to the numerous details later on. 
§3. The nebula, then must have rotated ; and there is no 
reason to doubt that it did. Ihtt let us remember that the 
vital point rieht here is to determine idiat caused the rotation. 
The importance of this point is further emphasized bv the fact 
that the same force must later on serve as the motive power for 
the rotation of all the bodies formed from the orioinal nebula. 
