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i^LDDRESS 



RECENT ADVANCES EX SPECTROSCOPY.* 



A. A. MiCHELSON. 



The fame of Newton rests chiefly on his epoch-making dis- 

 covery of the laws of gravitational astronomy — by means of 

 which the positions of the moons, the planets, and the comets, 

 and other members of our solar system can be calculated and 

 verified with the utmost precision, and in many cases such cal- 

 culation and verification may be extended to systems of suns 

 and planets outside our own. 



But in no less degree are we indebted to this monumental 

 genius for that equally important branch of astrophysics — inj 

 which the spectroscope plays so fundamental a role — by means 

 of which we are enabled to discover the physical and chemical 

 constitution of the heavenly bodies, as well as their positions 

 and motions. As the number and intricacy of the wonderful sys- 

 tems of stellar worlds which the telescope can reveal increase 

 with its power, so also do the evidences of the innermost molec- 

 ular structure of matter increase with the power of the spectro- 

 scope. If Newton's fundamental experiment of separating the 

 colors of sunlight had been made under conditions so slightly 

 different from those in his actual experiment that in the pres- 

 ent stage of experimiental science they would at once suggest 

 themselves to the veriest tyro, the science of spectroscopy would 

 have been founded. 



♦Nobel Lecture, delivered by A. A. Michelson before the Royal Academy of Science 

 at Stockholm, Dec. 12, 1907, and awarded the Nobel Prize. 



