232 CARNEGIE INSTITUTION OF WA.SHINGTON. 



the planets create in one another's orbits and by the special condi- 

 tions of aggregation, but remains essentially true. For the large 

 planets that have dominated their collecting zones and presumably 

 swept them thoroughly, the reductions of eccentricity are subequal. 

 For the very small bodies that presuraabh' grew but little, the eccen- 

 tricities remain large, for the greater part. For example, the eccen- 

 tricity of Mercury, the smallest of the planets, remains more than 

 twice that of any other planet. Mars, the next smallest in size, 

 comes next in eccentricity among the planets, while the asteroids, 

 which probably grew but little, have high eccentricities, as a rule. 

 Their orbits have doubtless been not a little disturbed by the great 

 influence of their powerful neighbor, Jupiter, and a rigorous appli- 

 cation of so general a law as the one under consideration can not be 

 made to the details of their orbits, but the tenor of the facts is very 

 suggestive. The highest eccentricity, 0.38, is as high as the highest 

 eccentricity assigned to the original nuclei of the planets. Of the 

 seventy asteroids whose diameters are fairl}- well known, the half 

 that are larger and presumablj- have grown most have less eccentric 

 orbits by 13.7 per cent than the half that are smaller and presum- 

 ably have grown less. Of the orbital elements of 278 asteroids ex- 

 amined, the half having the lowest inclination to the common plane 

 of the sj'stem, and so best suited for accretion, have eccentricities 

 21.9 per cent less than those of greater inclination. The orbits of 

 Neptune and Venus are exceptionally circular, the former, perhaps, 

 on account of its outermost position and mode of accretion, as pre- 

 viously suggested ; the latter for reasons not obvious. Rigorously 

 consistent results can not be expected from such antecedents as are 

 postulated in a case of this kind, and the mutual perturbations of 

 the planets introduce variations from the average eccentricities. The 

 degree of consistency noted is, perhaps, to be regarded as much 

 more remarkable than the departures from it. If this view of the 

 spacing out of the planets be entertained, a rational law may be 

 substituted for the purely numerical fornuilation known as Bode's 

 law, viz, that the spacing has been derived from a fairly consistent 

 variation in the primitive eccentricities of the planetesimals and 

 nuclei of the parent nebula, in which the outer were symmetrically 

 greater than the inner. 



It has thus been my endeavor to develop the hypothesis into suflEi- 

 cient detail ( i ) to furnish a large number of points of contact with 

 known phenomena and with recognized mechanical principles to 

 facilitate testing its verity by those relations, if not worn, at least in 



