504 EQUILIBRATION. 



mass ; but as soon as the second force has increased up to art 

 equality with the first, the equatorial portion can follow no 

 further, and remains behind. While, however, the resulting 

 ring, regarded as a whole connected by forces with external 

 wholes, has reached a state of moving equilibrium; its parts 

 are not balanced with respect to each other. As we be- 

 fore saw (§ 150) the probabilities against the maintenance 

 of an annular form by nebulous matter, are immense : from 

 the instability of the homogeneous, it is inferrable that nebu- 

 lous matter so distributed must break up into portions; 

 and eventually concentrate into a single mass. That is to 

 say, the ring must progress towards a moving equilibrium 

 of a more complete kind, during the dissipation of that 

 motion which maintained its particles in a diffused form: 

 leaving at length a planetary body, attended perhaps by a 

 group of minor bodies, severally having residuary relative 

 motions that are no longer resisted by sensible media; and 

 there is thus constituted an equilibrium mobile that is all but 

 absolutely perfect.* 



Hypothesis aside, the principle of equilibration is still 

 perpetually illustrated in those minor changes of state which 



* Sir David Brewster has recently been citing with approval, a calculation 

 by M. Babinet, to the effect that on the hypothesis of nebular genesis, the 

 matter of the Sun, when it filled the Earth's orbit, must have taken 3181 years 

 to rotate ; and that therefore the hypothesis cannot be true. This calculation 

 of Iff. Babinet may pair-off with that of M. Comte, who, contrariwise, made 

 the time of this rotation agree very nearly with the Earth's period of revolu- 

 tion round the Sun ; for if M. Comte's calculation involved a petitio principn, 

 that of M. Babinet is manifestly based on two assumptions, both of which are 

 gratuitous, and one of them totally inconsistent with the doctrine to be tested. 

 He has evidently proceeded on the current supposition respecting the Sun's 

 internal density, which is not proved, and from which there are reasons for 

 dissenting ; and he has evidently taken for granted that all parts of the neb- 

 ulous spheroid, when it filled the Earth's orbit, had the same angular velocity ; 

 whereas if (as is implied in the nebular hypothesis, rationally understood) this 

 spheroid resulted from the concentration of far more widely-diffused matter, 

 the angular velocity of its equatorial portion would obviously be immensely 

 greater than that of its central portion. 



