2 PLEASANT WA YS IN SCIENCE. 



list of known solar elements some which yet remain to be 

 detected ; but if Dr. Draper should thus have added but 

 one element to that list, he will ever be regarded as the 

 physicist to whose acumen the method was due by which all 

 were detected, and to whom, therefore, the chief credit of 

 their discovery must certainly be attributed. 



I propose briefly to consider the circumstances which 

 preceded the great discovery which it is now my pleasing 

 duty to describe, in order that the reader may the more 

 readily follow the remarks by which I shall endeavour to 

 indicate some of the results which seem to follow from the 

 discovery, as well as the line along which, in my opinion, 

 the new method may most hopefully be followed. 



It is generally known that what is called the spectro- 

 scopic method of analyzing the sun's substance had its origin 

 in Kirchhoff s interpretation of the dark lines in the solar 

 spectrum. Until 1859 these dark lines had not been 

 supposed to have any special significance, or rather it had 

 not been supposed that their significance, whatever it might 

 be, could be interpreted. A physicist of some eminence 

 spoke of these phenomena in 1858 in a tone which ought 

 by the way seldom to be adopted by the man of science. 

 "The phenomena defy, as we have seen," he said, "all 

 attempts hitherto to reduce them within empirical laws, and 

 no complete explanation or theory of them is possible. 

 All that theory can be expected to do is this it may explain 

 how dark lines of any sort may arise within the spectrum.'' 

 Kirchhoff, in 1859, showed not only how dark lines of any 

 sort may appear, but how and why they do appear, and 

 precisely what they mean. He found that the dark lines 

 of the solar spectrum are due to the vapours of various 

 elements in the sun's atmosphere, and that the nature of 

 such elements may be determined from the observed posi- 

 tion of the dark lines. Thus when iron is raised by the 

 passage of the electric spark to so intense a degree of heat 

 that it is vaporized, the light of the glowing vapour of iron 

 is found to give a multitude of bright lines along the whole 



