12 GEOLOGY. 



(8) So again, if the ratios of the masses separated at the successive 

 stages be compared with the momenta they carried off, very remark- 

 able discrepancies arise. In this case the moment of momentum of 

 the parent nebula at any stage may be computed from the moments 

 of momentum of its derivatives, and so all doubts that may arise from 

 the distribution of density in the nebula be avoided. For example, 

 the mass of the supposed ring that formed Jupiter and his moons was 

 less than one-thousandth part of the solar nebula at the stage at which 

 the ring was separated; but Jupiter and his moons now have about 

 95% of the total amount of moment of momentum of the whole nebula 

 at that stage. In other words, the Laplacian hypothesis involves 

 the proposition that in a rotating gaseous spheroid, an equatorial 

 ring equal to less than one-thousandth of the whole mass, in separating 

 by centrifugal acceleration, carried off 95% of the whole moment of 

 momentum, which seems incredible. A similar examination of the 

 separation of other rings gives like extraordinary results, and these 

 results, as in the previous case, vary greatly and irregularly among 

 themselves, showing a lack of system or consistency in the supposed 

 process of ring detachment. 



The inquiry along these lines, being of a somewhat rigorous mechani- 

 cal nature, throws grave doubt on the validity of the Laplacian hypothe- 

 sis. It seems to show that the solar system must have been organ- 

 ized so that a very small fraction of the matter (i.e., the planets and 

 satellites, which amount to about 1/700 of the whole system) carry 

 nearly all (97 + %) of the moment of momentum, leaving less than 

 3% in the central body that carries all of the matter but the minute 

 fraction named. It is difficult to see how this could arise from a rota- 

 ting spheroid. Tidal reaction, by transferring momentum from the 

 central to the outlying bodies, may help slightly to escape from the 

 difficulty, but computation shows that it is utterly inadequate to 

 meet the case. 



(9) Under the Laplacian hypothesis the satellites should all revolve 

 in the direction in which their planets rotate. The newly discovered 

 ninth satellite of Saturn revolves in a direction opposite to the planet 

 and the inner satellites. 



Unfavorable testimony of existing nebulae. — The hold of the Lapla- 

 cian hypothesis has been still further weakened by the fact that, 

 though the knowledge of existing nebula? has recently been extended 



