

SMITHSONIAN MISCELLANEOUS COLIlECTIONS ^''^2 



VOLUME 87. NUMBER 4 \ /^i*K 



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fo 





J^esearcl) Corporation iFunb 



THE PERIdUOMETER: AN INSTRUMENT 



FOR FINDING AND EVALUATING 



PERIODICITIES IN LONG SERIES 



OF OBSERVATIONS 



(With One Plate) 



BY 

 G. G. ABBOT 



Secretary, Smithsonian Institution 



(Publication 3138) 



GITY OF WASHINGTON 



PUBLISHED BY THE SMITHSONIAN INSTITUTION 



FEBRUARY 6, 1932 



