50 ILLINOIS ACADEMY OF SCIENCE 
A less technical argument may be appreciated by laymen, 
who may readily picture to themselves the solar nebula just 
before the matter of Jupiter and his satellites was separated 
from it according to this hypothesis. The mass of the Jovian 
matter was less than one-thousandth part of the mass of the 
nebula at that stage. A rough estimate may easily be made 
of the momentum that could be carried by this little outer rim 
of one-thousandth part compared with that carried by the 
remaining 999 parts. It is obvious from even a mere inspection 
that the moment of momentum of the thousandth part could 
only be some minor portion of the whole. But yet the Jovian 
system actually has more than nineteen times as much moment 
of momentum as all the inner bodies, including the sun, which 
were supposed to have been formed from the rest of the ne- 
bula. It seems incredible that the material for the Jovian 
system could have been separated in this way. A like in- 
spection of other supposed centrifugal separations leads to 
analogous discrepancies, some of them proportionately more 
remarkable. 
The cumulative force of the objections to the centrifugal 
hypothesis seems too grave to be escaped by any special plead- 
ing. This does not mean that centrifugal separation cannot 
give rise to planetary matter in any case, but merely that 
origin by such separation does not fit the requirements of our 
present planetary system. 
The satellites also offer a silent protest against the pedigree 
assigned them by the centrifugal hypothesis. The orbital 
speeds of Phobos and the small bodies that form the inner ring 
of Saturn demur. They cannot consistently concur in the im- 
plications of the centrifugal pedigree. Particularly sharp 
is the dissent of three satellites recently found to revolve 
in directions not only contrary to the postulates of the hypo- 
thesis but opposite to their fellow satellites attending the same 
planets. 
In the face of these serious difficulties—not to cite others 
—there seems to me no alternative but to abandon the hypoth- 
esis that our present planets and the stun were formed in close 
succession from a common nebula by centrifugal separation. 
Some other mode of origin must be found that better tallies 
with the significant facts of the system. Obviously it must 
