Prof. P. E. Chase on Momentum andYi^ viva. 291 



of 25 per cent., been dissociated, the quantity of the latter 

 formed Avould be obtained directly from the value x. These 

 assumptions, however, are not strictly correct ; and, moreover, 

 the acid and base resultino- from the dissociation mioht act 

 further upon the other constituents of the solution, and conse- 

 quently a change in the combining-proportions might ensue. 

 Leipzig, October 1876. 



XXXYIII. On the Nebular Hypothesis. — VI. Momentum and 

 Vis viva. By Pliny Earle Chase, LL.D., S.P.A.S., 



Professor of Philosophy in Haverford College. 



[Coutiniied from vol. iii. p. 211.] 



IT is often more difficult to grasp truths which are presented 

 under new aspects than those which are clothed in fami- 

 liar garbs. It may therefore be well to glance at some of the 

 most obvious tendencies to nodal action which result from 

 simple gravitating fall towards a centre. The examination 

 will be the more interesting and suggestive, because like ten- 

 dencies must exist in all central forces which vary inversely 

 as the square of the distance. 



Ennis* has called attention to the fact that the difference 

 between the velocity of infinite radial fall ( V 2 gr) and cir- 

 cular-orbital velocity {^y gr) must be accounted for in some 

 way; and he thinks that it may be sufficient to explain all the 

 phenomena of planetary rotation and revolution. In nebular 



condensation from r to - the increase of radial velocity is 



(^s/n—\)'^^2gr\ the circular-orbital velocity at - is s/ngr-, 



therefore the increment of radial velocity would be sufficient 

 to produce orbital velocity, in the periphery of an originally 

 stationary nebula, when (V^^~l)\/2=\/n; and 



If T be made to represent successively all points between se- 

 cular aphelion and secular perihelion in the hypothetical nebu- 

 lous belts which were condensed into Neptune, Uranus, 

 Saturn, and Jupiter, this fall of condensation from Neptune 

 would give orbital velocities in the Asteroidal belt; from 

 Uranus, in the Mars belt; from Saturn, in the Venus belt; 

 and from Jupiter, in the Mercury belt. Earth, as I have 

 already shown, is at the centre of the primitive inter-asteroidal 



* Phil. Mag. April 1877, pp. 2G2 sqq. 

 U2 



