RECENT COSMOGONIES 233 



for the rotation of the Laplacian nebula the former, by 

 its direct condensation, and the latter, by the resolution 

 of its multitudinous interior conflicting currents into a 

 uniform gyratory resultant. The primary desideratum 

 in both these hypotheses, in the hypothesis of Laplace 

 himself in all the hypotheses, indeed, that center about 

 this nebular conception is not so much to account for 

 the rotatory motion of the nebula, as such, as to supply 

 the agency for starting the planets and satellites into 

 concerted vortical movement. In brief, the ruling idea 

 is that these bodies derived their motions immediately 

 from their parent nebula as integral with it, and not 

 from any independent, extraneous source. That Doctor 

 See shares this view clearly appears from the quotation 

 already given (v. p. 11), in which he says, inter alia: 

 6 ' Spiral nebulae arise from the meeting or mere settling of 

 unsymmetrical streams of cosmical dust. The whole 

 system of particles has a sensible moment of momentum 

 about some axis, and thus it begins to whirl about some 

 central point, and gives rise to a vortex. * * The dust 

 carried away from the stars by repulsive forces gathers 

 here and there into clouds, and when such a mass settles 

 the result is a cosmical vortex, which whirls and slowly 

 develops into a system ". 



It will be remembered with what scrupulous care 

 Newton strove to impress upon the world the notion that 

 cosmic space is absolutely clear of any ponderable 

 medium. Why! Because he recognized, even if his suc- 

 cessors affect ignorance of it, the absolute necessity, 

 under his theory, that the infinitely accurate adjustments 

 between gravity on the one hand and the tangential veloc- 

 ity of the circulating body on the other, ordained, as he 

 postulated, by the Creator, dare not on any account be 

 altered, even in the slightest, without immediately and 

 irretrievably destroying (not merely imperiling) the 

 whole system. Since his day, however, a few phenomena, 

 such as the moon's acceleration and the acceleration of 

 Encke's comet, have come to light that have put the 

 mathematicians sadly at a loss to explain gravitationally, 



