Masterpieces of Science 



research can revise the original observation 

 by. another and independent examination of the 

 photograph. " During the eight years beginning 

 with 1892, four stars of more than the ninth 

 magnitude were added to the charts of astron- 

 omy; in every case the discoverer was Mrs. 

 Fleming as she detected the spectrum of a new 

 star in celestial photographs. 



Professor J. Clerk-Maxwell was of the opinion 

 that the rings of Saturn are simply aggregates of 

 meteorites which preserve their outline by swift 

 rotation. His belief has been verified by Pro- 

 fessor Keeler at the Allegheny Observatory, 

 his spectroscope proving that the inner edge of 

 each ring moves more swiftly than the outer 

 edge. If the ring were a solid body the reverse 

 would be the fact, and the lines in its spectrum 

 would be very nearly continuations of the lines 

 in the spectrum of the central ball. So refined 

 is this field of inquiry that the astronomer's 

 reliance is upon a micrometer exquisite enough 

 to measure a space of one ten-thousandth of an 

 inch on a photograph.* 



The latest chapter in the history of the solar 

 spectrum has been added by Professor George E. 

 Hale, director of the Yerkes Observatory. An 

 ordinary spectroscope has a slit through which 

 a narrow ray of light passes into a prism for dis- 

 persion. To this slit Professor Hale adds an- 



* "Some Notes on the Application of Photography to the 

 Study of Celestial Spectra," by James E. Keeler, Photo- 

 graphic Times, May, 1898. 



94 



