OXYGEN IN THE SUN. 27 



enlisting fresh recruits in the work of observation, and many 

 of these may before long be heard of as among those who 

 have employed Dr. Draper's method successfully. 



But I would specially call attention to the interest which 

 attaches to Dr. Draper's discovery and to the researches 

 likely to follow from it, in connection with a branch of re- 

 search which is becoming more and more closely connected 

 year by year with solar investigations I mean stellar spec- 

 troscopy. We have seen the stars divided into orders 

 according to their constitution. We recognize evidence 

 tending to show that these various orders depend in part 

 upon age not absolute but relative age. There are among 

 the suns which people space some younger by far than our 

 sun, others far older, and some in a late stage of stellar 

 decrepitude. Whether as yet spectroscopists have perfectly 

 succeeded in classifying these stellar orders in such sort that 

 the connection between a star's spectrum and the star's age 

 can be at once determined, may be doubtful. But certainly 

 there are reasons for hoping that before long this will be 

 done. Amongst the stars, and (strange to say) among 

 celestial objects which are not stars; there are suns in every 

 conceivable stage of development, from embryon masses 

 not as yet justly to be regarded as suns, to masses which 

 have ceased to fulfil the duties of suns. Among the more 

 pressing duties of spectroscopic analysis at the present time 

 is the proper classification of these various orders of stars. 

 Whensoever that task shall have been accomplished, strong 

 light, I venture to predict, will be thrown on our sun's present 

 condition, as well as on his past history, and on that future 

 fate upon which depends the future of our earth. 



