Prof. D. Kirkwood on the Nebular Hypothesis. 171 
space, to revolve as burning globes around itself, or the centre of 
gravity of the whole. But what would be the condition of one 
8. The Satellites—It is a remarkable coincidence in regard to 
the motions of the moon that her rotation is completed in a period 
Precisely equal to that of her orbital revolution. ‘The same is 
ably, indeed, of all secondaries. Such coincidences are pe to 
be ascribed to chance. Either, therefore, we must regard them: 
be inclined t ‘ ; 
ors oOadopt the former alternative. 
the philosophic nee is for explanation, 1. @, for the breaking up 
2 complex phenomena into familiar sequences, at There 
* Monthly Notices of 9th, 1856. 
, the Roy. Astr. Soc. for May sa % 
t Edinburgh Review, No. ore: + Principia, B. iii, Prop. xxxvii, Cor. 
