THE ORIGIN AND DEVELOPMENT OF THE EARTH 105 
the ring, the greater the moment of momentum. Now the 
mass of material composing the ring from which Jupiter and 
his suns supposedly descended was about one one-thousandth 
part of that of the parent nebula at that particular stage of 
its development, but these same planet and satellites contain 
95 percent of the solar nebula at that stage. Equally striking 
discrepancies appear when the momentum of the other 
planets is considered. In other words, the Laplacian hypo- 
thesis seems to demand that the solar system be so organized 
that the planets and satellites, amounting to about one seven- 
hundredth of the total mass of the system, were able to carry 
off more than 97 percent of its total momentum. There is no 
law of physies or astronomy that will allow for such «@ 
condition. . 
So far, the arguments against the nebular hypothesis which 
we have considered have been principally astronomical, and 
eredit for their discovery and elaboration must be given to 
‘Dr. F. R. Moulton, the first astronomer to seriously consider 
the difficulties in the way of Laplaceism. There are other 
arguments, perhaps equally strong, coming from the geolo- 
gists and paleontologists, but these will be left for considera- 
tion farther on in the paper. On the whole, the Laplacian 
hypothesis must be given up. The idea of a molten globe 
which is gradually cooling and losing its atmosphere; of the 
moon as a dead body, and the earth and Mars as dying ones 
is very poetic but it fails to stand the test of modern science. 
Writers of feature articles for Sunday papers, and of “popu- 
‘lar’ books on alleged science still favor the old idea, for it 
works up excellently into sensational treatment. We must, 
however, as did geologists and astronomers of thirty years 
ago, look for another solution. 
2.—The Meteoritic Hypotheses. 
No matter how great the popularity of any hypothesis there 
are bound to be people who will disagree with it and advance 
other ideas, and the Laplacian hypothesis was no exception to 
this rule. Hundreds, even thousands of years before La- 
place’s time it had been noted that “shooting stars” enter the 
atmosphere in great numbers, and that occasionally fragments 
of stony or metallic material fall to the earth. From the ob- 
