178 PIONEERS OF EVOLUTION. 



is reached in the infinitely diverse forms of plants 

 and animals. Therefore, as our knowledge of matter 

 is limited to the changes of which we assume it to 

 be the vehicle, it would seem that science reduces 

 the Universe to the intelligible concept of Motion. 



Since the great discovery by Kirchofif, in 1859, 

 of the meaning of the dark lines that cross the 

 refracted sun-rays, the spectroscope has come as 

 powerful evidence in support of the nebular theory, 

 while the photographic plate is a scarcely less im- 

 portant witness. The one has demonstrated that 

 many nebulae, once thought to be star-clusters, are 

 masses of glowing hydrogen and nitrogen gases; 

 that, to quote the striking communication made by 

 the highest authority on the subject. Dr. Huggins, 

 in his Presidential Address to the British Associa- 

 tion, 1891, " in the part of the heavens within our 

 ken, the stars still in the early and middle stages of 

 evolution exceed greatly in number those which 

 appear to be in an advanced condition of condensa- 

 tion." The other, recording infallible vibrations on 

 a sensitive plate, and securing accurate registration 

 of the impressions, reveals, as in Dr. Roberts's grand 

 photograph of the nebula in Andromeda, a central 

 mass round which are distinct rings of luminous 

 matter, these being separated from the main body 

 by dark rifts or spaces. To quote Dr. Huggins once 

 more, " We seem to have presented to us some stage 

 of cosmical Evolution on a gigantic scale." 



The great fact that lies at the back of all these 



