ASTRONOMY AS A SCIENCE. THE SUN. 119 



show the existence in the media enveloping the body 

 of the sun (photosphere, chromosphere, or by whatever 

 name designated) of various metallic elements and gases 

 familiar to us on the surface of the earth. The methods 

 by which certainty has been given to this wonderful 

 result, while they illustrate the physical relations of all 

 that is greatest and smallest in the material world, do 

 also strikingly express that growth of intellectual power 

 through which man has reached a knowledge thus far 

 beyond that of all prior ages ; beyond even what might 

 seem the destined limit of human attainment. Nor is 

 any such limit yet obvious to us. The very negation 

 of various terrestrial metals, shown by the absence in 

 the solar light of the lines interpreting them, and the 

 existence of lines in the spectrum to which we have no 

 index in our earthly catalogue, are facts equally preg- 

 nant for the future. Even while writing this paper, 

 with intent to illustrate by solar researches the present 

 aspect and aims of astronomical science, these re- 

 searches are in active, almost daily, progress ; bringing 

 before the eye movements and changes ever going on 

 upon the surface of this vast central luminary pheno- 

 mena which, though of surpassing grandeur in their 

 scale, depend upon the presence in the sun of certain 

 material elements identical with matters ever present 

 and active on our own globe. It is well to note here, 

 as an index to the mutual relations of the physical 

 sciences, that chemistry, optics, electricity, and tele- 

 scopic observation are all concerned and blended in 

 the methods to which these discoveries are due. 



We see the sun, then, no longer as a simple central 



