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POPULAR SCIENCE MONTHLY. 



it undesirable to follow the matter I since that date, and that by Professor 



Young himself at Princeton. In 1876, 

 expedition to with the first grating spectroscope used 

 Wyoming in the summer of 1872, to | in astronomical work, he made the 



further at that time. 

 Professor Young's 



Professor Charles A. Young. 



utilize the advantages of an altitude of 

 over eight thousand feet, added a hun- 

 dred chromospheric lines to the list of 

 170 which he had observed at Dart- 



pioneer measurements of the rotation 

 of the sun from the relative displace- 

 ments of lines on the approaching and 

 receding: limbs. We are indebted to 



mouth. It may be mentioned that this \ him for important observations on the 

 list has been but slightly enlarged j spectrum of sun-spots, made after his 



