ADVANCE OF ASTRONOMY. 219 



this is only one of many results with which spectrum 

 analysis has enriched astronomy. Thus we might 

 refer to the remarkable argument from spectroscopy 

 which led Pickering of Harvard in 1889 to infer that 

 a certain star in Ursa was really double, or Vogler 

 to confirm the suggestion that the variability of 

 Algol was due to its being periodically eclipsed by 

 a dark or nearly dark companion star. In short, 

 besides chemical information, the spectroscope affords 

 a means of determining celestial motions in the line 

 of sight, and has detected binary which the telescope 

 could never have revealed. 



Sir William Huggins writes : " In no science, 

 perhaps, does the sober statement of the results which 

 have been achieved appeal so strongly to the imagina- 

 tion, and make so evident the almost boundless 

 powers of the mind of man. By means of its light 

 alone to analyse the chemical nature of a far dis- 

 tant body ; to be able to reason about its present state 

 in relation to the past and future ; to measure within 

 an English mile or less per second the otherwise invis- 

 ible motion which it may have towards us or from 

 us ; to do more, to make even that which is darkness 

 to our eyes light, and from vibrations which our 

 organs of sight are powerless to perceive, to evolve a 

 revelation in which we see mirrored some of the 

 stages through which the stars may pass in the 

 slow evolutional progress surely the record of such 

 achievements, however poor the form of words in 

 which they may be described, is worthy to be re- 

 garded as the scientific epic of the century. " * 



The extension of spectrum analysis to the stars 

 has yielded information as to the chemical elements 

 which occur in them, has distinguished gaseous neb- 



* President's address. Rep. Brit. Ass. for 1891, p. 4. 



