THE ORIGIN OF THE EARTH. 79 



mals of larger and smaller orbits gathered in by them. Assuming 

 these to have been somewhat equable, the planetary distribution should 

 be roughly proportional to the eccentricities of the nuclear orbits. As 

 a basis for inspection, let it be supposed that the collecting zone of each 

 planet reaches half-way to its neighbor on either hand; and let the 

 eccentricity of the orbit of each nucleus be such that the nucleus itself 

 shall sweep its whole collecting zone, which is more than the case 

 absolutely requires. The following are the eccentricities so derived, 

 compared with present eccentricities: 



Assigned Present 



Eccentricity. Eccentricity. 



Nucleus of Mercury 25 ± .2 



Venus 21 .006 



Earth 20 .017 



Mars 28 .093 



. . . __ __ land less; mean 



Asteroids (mean) 33 .38 f , ' 



Jupiter 336 .048 



Saturn 366 .056 



Uranus .37 .046 



Neptune 38± .009 



There being no known planet outside of Neptune, the method can 

 only be applied to it by an arbitrary assumption regarding its outside 

 collecting area. It may be reasonably assumed that the nucleus of 

 Neptune represented the head of the protuberance, so to speak, and 

 that its accretion was essentially all on the inner side, which would draw 

 its orbit inward, according to the principle above stated. This may 

 account for its anomalous spacing out. There being no known planet 

 inside Mercury, the eccentricity assigned it is also in a measure arbi- 

 trary. 



With these qualifications, it will be seen that the assigned eccentrici- 

 ties are quite harmonious, and on the whole they indicate a progressively 

 greater original eccentricity from within outward. By comparison 

 with the existing eccentricities, it will be seen that the assigned original 

 ones are much the more consistent. The reason for this, under our 

 hypothesis, is close at hand. According to the principle of evolution 

 from eccentricity toward circularity, stated above, the greater the 



