SCO COSMIC FJIILOSOPJ1 Y. [pt. il 



filling Neptune's orbit, must have consisted of diffused 

 vaporous matter, like that of which the irresolvable nebulte 

 have recently been proved to consist. Now in the slow 

 concentration of the matter constituting this solar nebula, 

 as both Kant and Laplace have elaborately proved, the 

 most prominent peculiarities of the solar system find their 

 complete explanation. Supposing the sun to have been 

 once a mass of nebulous vapour, extending in every 

 direction far beyond the present limits of the solar system, 

 these thinkers proved that the mere contraction of such 

 a mass must inevitably have brought about just the 

 state of things which we now find. Let us observe some 

 of the processes which must have taken place in this 

 nebulous mass. 



Note first that we are obliged to accredit the various parts 

 of this genetic nebula with motions bearing some reference to 

 a common centre of gravity ; for the rotation of the resulting 

 system must have had an equivalent amount of motion for 

 its antecedent, and it is a well-known theorem of mechanics 

 that no system of bodies can acquire a primordial rotation 

 merely from the interaction of its own parts. In making 

 this assumption, however, we are simply carrying out the 

 principle of the continuity of motion. It is not necessary to 

 suppose, in addition, that all these motions primordially con- 

 stituted a rotation of the whole mass in one direction. Such 

 a hypothesis seems to me not only gratuitous, but highly im- 

 probable. It is more likely that these primeval motions took 

 the shape of currents, now aiding and now opposing one 

 another, and determined hither and thither according to local 

 circumstances. In any case, such indefiniteness of movement 

 must finally end in a definite rotation in one direction. For 

 unless the currents tending eastward are exactly balanced 

 by the currents tending westward — a supposition against 

 which the chances are as infinity to one — the one set must 

 Eventually prevail over the other. And after some such 



