A HISTORY OF SCIENCE 



fate by assuming, as the original speculation assumed, 

 that this is a culminating and final stage of cosmic ex- 

 istence. For the dark star, though its molecular ac- 

 tivities have come to relative stability and impotence, 

 still retains the enormous potentialities of molar mo- 

 tion ; and clearly, where motion is, stasis is not. Sooner 

 or later, in its ceaseless flight through space, the dark 

 star must collide with some other stellar body, as Dr. 

 Croll imagines of the dark bodies which his " pre-nebu- 

 lar theory" postulates. Such collision may be long 

 delayed ; the dark star may be drawn in comet-like cir- 

 cuit about thousands of other stellar masses, and be 

 hurtled on thousands of diverse parabolic or elliptical 

 orbits, before it chances to collide but that matters 

 not: "billions are the units in the arithmetic of eter- 

 nity," and sooner or later, we can hardly doubt, a col- 

 lision must occur. Then without question the mutual 

 impact must shatter both colliding bodies into vapor, 

 or vapor combined with meteoric fragments ; in short, 

 into a veritable nebula, the matrix of future worlds. 

 Thus the dark star, which is the last term of one series 

 of cosmic changes, becomes the first term of another 

 series at once a post-nebular and a pre-nebular con- 

 dition; and the nebular hypothesis, thus amplified, 

 ceases to be a mere linear scale, and is rounded out to 

 connote an unending series of cosmic cycles, more 

 nearly satisfying the imagination. 



In this extended view, nebulae and luminous stars are 

 but the infantile and adolescent stages of the life his- 

 tory of the cosmic individual; the dark star, its adult 

 stage, or time of true virility. Or we may think of the 

 shrunken dark star as the germ-cell, the pollen-grain, of 



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