SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOLUME 87. NUMBER 4 



iaesearcl) Corporation iFuntJ 



THE PERIODOMETER: AN INSTRUMENT 



FOR FINDING AND EVALUATING 



PERIODICITIES IN LONG SERIES 



OF OBSERVATIONS 



(With One Plate) 



BY 

 G. G. ABBOT 



Secretary, Smithsonian Institution 



(Publication 3138) 



GUY OF WASHINGTON 



PUBLISHED BY THE SMITHSONIAN INSTITUTION 



FEBRUARY 6, 1932 



