418 GEOLOGY 



into a spheroid as simply and promptly as postulated by this 

 theory. 



3. In the highly heated condition assigned the earth -moon 

 ring, its gravity could hardly have held the common gases together, 

 because of their intense molecular activities. The earth, even 

 now, does not appear to be able to hold permanently very light 

 gases, though it does hold the heavier ones which have slower 

 molecular velocities. 



4. It is probable that the attenuated substance of a ring, 

 such as the supposed earth-moon ring, would have cooled to solid 

 particles long before it could collect into a spheroid, and hence no 

 secondary ring to form a moon would be developed. 



5. The inner satellite of Mars (Phobos) revolves about that 

 planet three times while the planet rotates once. According to 

 the Laplacian theory they must have rotated together at the 

 time of separation, and the planet should have kept on in- 

 creasing its rotation by cooling after the separation. Its period of 

 rotation should therefore have been shorter than the period of the 

 satellite's revolution. It has been suggested that the planet's rota- 

 tion was lengthened by its tides, but so much lengthening is very 

 unlikely. If accepted in this case, it is hard to apply it consist- 

 ently to the similar anomaly of the small bodies that make up the 

 inner edge of the inner ring of Saturn, and they revolve in about 

 half the time of that planet's rotation. 



6. If the solar system were converted into a gaseous spheroid. 

 and so expanded as to reach out to Neptune's orbit, and had its 

 matter distributed according to the laws of gases, and if this nebula 

 were endowed with the total value of the momentum (technically 

 the moment of momentum) now possessed by the solar system, it 

 would not have had a rate of rotation rapid enough to detach 

 matter from its equator at that stage, or at any later stage until 

 it had contracted well within the orbit of the innermost planet. 



7. If the expanded spheroid were given the rates of rotation 

 necessary to shed rings at the proper stages (if rings could be 

 formed), the moment of momentum at each stage must h:iv> 

 equalled that of the matter it then contained; for the total moment 

 of momentum of any such system must remain constant so far as its 



