168 THE CHEMISTRY OF THE STARS. 



tlie domain of human thought and help us to understand the mechanism 

 of the wonderful universe in which our lot is cast, as well as those 

 which add to the comfort and the convenience of our lives. 



It would be also easy to show by many instances how researches, 

 considered ideally useless at the time they were made, have been the 

 origin of the most tremendous applications. One instance suffices. 

 Faraday's trifling with wires and magnets has already landed us in one 

 of the greatest revolutions which civilization has witnessed; and where 

 the triumphs of electrical science will stop no man can say. 



This is a case in which the useless has been rapidly sublimed into 

 utility so far as our material wants are concerned. 



I propose to bring to your notice another "useless" observation sug- 

 gesting a line of inquiry which 1 believe sooner or later is destined 

 profoundly to influence human thought along many lines. 



Fraunhofer at the beginning of this century examined sunlight and 

 starlight through a prism. He found that the light received from the 

 sun differed from that of the stars. So useless did his work appear 

 that we had to wait for half a century till any considerable advance 

 was made. It was found at last that the strange "lines" seen and 

 named by Fraunhofer were precious indications of the chemical sub- 

 stances present in worlds immeasurably remote. We had, after half a 

 century's neglect, the foundation of solar and stellar chemistry, an 

 advance in knowledge equaling any other in its importance. 



In dealing with my subject I shall first refer to the work which has 

 been done in more recent years with regard to this chemical condition- 

 ing of the atmospheres of stars, and afterwards very briefly show how 

 this work carries us into still other new and wider fields of thought. 



The first important matter which lies on the surface of such a general 

 inquiry as this is that if we deal with the chemical elements as judged 

 by the lines in their spectra we know for certain of the existence of 

 oxygen, of nitrogen, of argon, representing one class of gases, in no 

 celestial body whatever; whereas, representing other gases, we have a 

 tremendous demonstration of the existence of all the known lines of 

 hydrogen and helium. 



We see, then, that the celestial sorting out of gases is quite different 

 from the terrestial one. 



Taking the substances classed by the chemist as nonmetals, we find 

 carbon and silicium — I prefer, on account of its stellar behavior, to call 

 it silicium, though it is old fashioned — present in celestial phenomena. 

 We have evidence of this in the fact that we have a considerable devel- 

 opment of carbou in some stars and an indication of silicium in others. 

 But these are the only nonmetals observed. Now, with regard to the 

 metallic substances which we find, we deal chiefly with calcium, stron- 

 tium, iron, and magnesium. Others are not absolutely absent, but their 

 X>ercentage quantity is so small that they are negligible in a general 

 statement. 



