NIK 1.1 M ITS OF' SCIENCE. 301 



Geology, to begin with, is of little use in taking us over really 

 great distances of time: it may deal fairly accurately with a few 

 tens of millions of years, and show us how organic and inorganic 

 matter has behaved since the crust of our globe got cool enough 

 to permit of organic life, but it is mainly to astronomy that we 

 have to turn again to take Up to the houndary of science in this 

 direction ; hack past the era of the formation of the primary 

 rocks, to the glohe as a floating hall of molten matter; hack to a 

 time hefore it had even condensed from a vapour to a liquid, when 

 the moon was not distinguishable apart from our own centre of 

 vapour ; back to the time when what was to be the earth would 

 only just be distinguishable, as a world in the making, from the 

 great flat spiral nebulous mass of the sun, that extended far 

 Deyond it, beyond the orbit of our most distant brother planet, 

 Neptune. That brings us about as far back as the Nebular hypo- 

 thesis will take us, but one more theory has to be taken into con- 

 sideration before we can say that science is exhausted in record- 

 ing the ancient history of the universe. Science has to give a 

 reason to account for this mighty mass of matter, possessing such 

 a prodigious amount of heat as to cause it to be so rarefied 

 and nebulous a state, so she tells us that there has just been a 

 terrific collision : two bodies, perhaps both icy cold and dark, of 

 the aggregate weight of our solar system, and consisting of the 

 same elements, were drawn together by gravity, and possibly 

 some additional momentum of their own, and in one moment the 

 solid is transformed into gaseous ; unknown cold to untold heat, 

 and blackest darkness to brightest light. " The Impact Theory " 

 has taken us to the Limit of time for the future, as zuell as for the 

 past ; for our two black globes of matter are only such as we and 

 our sun will become some day, when all our heat has been radi- 

 ated into space; but science cannot go any further, or venture to 

 give us the date when these dark or shining suns arrived to form 

 a part of the Material Universe. Possibly there is a still wider 

 cycle, for we have to account for the apparently enormous waste 

 of material and energy being thrown out continually in all direc- 

 tions by all hot stellar bodies. It is thought that the matter, 

 largely composed of dust, thrown out beyond the reach of gravity 

 by violent storms, eruptions, and explosions, from these bodies, 

 is carried by heat and light waves to the darkest parts of space, 

 and there accumulates by its own gravity till a globe is formed, 

 which then must wait for a chance collision before the next step 

 in its evolution is made. The time required for this must cer- 

 tainly be enormously greater than the cycle already considered, 

 but, after all, we have not the satisfaction of feeling that we get 

 appreciably nearer the beginning or end of time, however much 

 our cycles are enlarged. 



V. JJ 7 hat is the ultimate force in the Material Universe? — 

 How far will science take us in the elucidation of this question? 

 Just as we feel convinced that all matter is, if we could only find 

 it, composed of one ultimate element, so we feel sure that the 



