74 STATEMENT AND EXPOS ITIOJN' OF 



of course, again, the masses are very nearly in the inverse ratio of the squares of 

 the distances/ 



The history of the changes would then seem to be: — 



1. That the division of the great masses, Neptune and that composed of Uranus 

 and /Saturn, first occurred ; in accordance with a proportion of masses and powers 

 of distances, such as Jupiter and Saturn now present. 



2. That afterward occurred the division of the compound Uranus- Saturn mass 

 into the masses of the whole-planet (Uj and the ancient Saturn i{. 



3. That subsequently to that, the material of the whole-planet (U) was rent [the 

 outer half-planet Uranus possibly falling inward somewhat, to justify the new 

 equilibrium of forces];^ and, (43), the material of the inner half-planet ^i passing 

 over and combining with the ancient Saturn 1^, to form the mass in part of the 

 existing Saturn h- 



4. That, be/ore the planetary character of Saturn was complete, the mass [derived 

 in great part, it may be, from the atmosphere of the other half-spheroid of the 

 sun],^ which was to form Jupiter, became temporarily blended with the Saturn- 

 mass ; to be in the end separated in accordance with the same law of arrangement 

 of masses and distances which, at first, was prevalent in the instance of the great 

 masses, Neptune and the combination of Saturn-Uranus.^ 



(105) It will be observed, that the preservation of the continued equality of 

 ratios here in question, depends upon the introduction, in one connexion, of the 

 ancient Saturn, that is Saturn deprived of the very mass acquired by the process 

 which brought about the disappearance of the mass of the interior half-planet §i, 

 as the same is described in (43) and (44), and the proof of which is manifold; 

 while the preservation of an equality of ratios in another connexion is as truly 

 dependent on the nitroduction of the ivliole mass of the existing Saturn. 



Such are the facts; and no explanation appears, except that of the process 

 which bore away the mass of the interior half-planet, the reality of which seems 

 thus, again, to be confirmed ; to which, possibly, may be added the mode of sub. 

 sequent combination and separation suggested in (104). 



Then we have the negative evidence, that the supposititious separation of the 

 great masses in question in any other way, is not found to yield at all similar pro- 

 portions. 



Kirhwood's Analogy. 



(106) This Prof. Daniel Kirkwood communicated to the American Association 

 for the Advancement of Science in 1849.^ 



He first speaks of Avhat, (39), Ave have described as the neutral point. 



Thus, as Prof. Kirkwood states it (and the same is applied to the Earth in our 



' The existing and vot the. ancient Saturn appearing here. ' See 5 of (43). 



= See ("99) and Note. 



" In this eonnesion-see, again, ArtirUs (56) and (5^). ' Proceedings, p. 208. 



