5 o6 THE POPULAR SCIENCE MONTHLY. 



as they clashed with one another in bodily impact around the central 

 core. Each star, thus produced, forever gathers in materials from its 

 own outlying mass, or from meteoric bodies, upon its solidifying nu- 

 cleus, and forever radiates off its store of associated energy to the hy- 

 pothetical surrounding ether. The fullest expression of this profound 

 cosmical conception has been given in our own time by Tait and 

 Balfour Stewart, working in part upon the previous results of Kant. 

 Laplace, the Herschels, Mayer, Joule, Clerk Maxwell, and Sir William 

 Thomson. Deeply altered as the nebular hypothesis has been by the 

 modern doctrine of correlation and conservation of energies, and by 

 modern researches into the nature of comets, meteors, and the sun's 

 envelopes, it still remains in its ultimate essence the original theory 

 of Kant and Laplace. 



Science has thus, within the period of our own half-century, exhib- 

 ited to us the existing phase of the universe at large in the light of 

 an episode in a single infinite and picturable drama, setting out long 

 since from a definite beginning, and tending slowly to a definite end. 

 Other phases, inconceivable to us, may or may not possibly have pre- 

 ceded it ; yet others, equally inconceivable, may or may not possibly 

 follow. But as realizable to ourselves, within our existing limitations, 

 the physical universe now reveals itself as starting in a remote past 

 from a diffuse and perhaps nebulous condition, in which all the mat- 

 ter, reduced to a state of extreme tenuity, occupied immeasurably 

 wide areas of space, while all the energy existed only in the potential 

 forms as separation of atoms or molecules ; and the evidence leads 

 us to look forward to a remote future when all the matter shall be 

 aggregated into its narrowest possible limits, w T hile all the energy, hav- 

 ing assumed the kinetic mode, shall have been radiated off into the 

 ethereal medium. Compared to the infinite cosmical vistas thus laid 

 open before our dazzled eyes, all the other scientific expansions of our 

 age shrink into relative narrowness and insignificance. 



As in the cosmos so in the solar system itself, evolutionism has 

 taught us to regard our sun, with its attendant planets and their 

 ancillary satellites, all in their several orbits, as owing their shape, 

 size, relations, and movements, not to external design and deliberate 

 creation, but to the slow and regular working out of physical laws, in 

 accordance with which each has assumed its existing weight, and bulk, 

 and path, and position. 



Geology here takes up the evolutionary parable, and, accepting on 

 trust from astronomy the earth itself as a cooling spheroid of incan- 

 descent matter, it has traced out the various steps by which the crust 

 assumed its present form, and the continents and oceans their present 

 distribution. Lyell here set on foot the evolutionary impulse. The 

 researches of Scrope, Judd, and others into volcanic and hypogene 

 action, and the long observations of geologists everywhere on the 

 effects of air, rain, ice, rivers, lakes, and oceans, have resulted in 



