FUNDAMENTAL PROBLKMS OF GEOLOGY. 23 1 



actual distribution of the planets and be an explanation of it. This 

 distribution should correspond to the eccentricities of the nuclei, 

 modified by the proportions of planetesimals 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 o.25± 0.2 



Venus 21 .006 



Earth 2 .017 



Mars 28 .093 



Asteroids (mean) 33 .38 downward.* 



Jupiter 336 .048 



Saturn 366 .056 



Uranus 37 -"46 



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 tlie 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 

 arbitrar>\ 



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

 tricities 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 accretion the greater the progress toward cir- 

 cularity. This is qualified somewhat by the perturbations which 



* Mean about 0.15. 



