[Annals N.Y. Acad. Sci., Vol. XVIII, No. 9, Part III, pp. 385-424. 29 August, 1908.] 



l^iBRARY 

 NEW YORK 

 BOTANICAL 



UaKDEN. 



AN INVESTIGATION OF THE FIGURE OF THE SUN AND 

 OF POSSIBLE VARIATIONS IN ITS SIZE AND SHAPE. 



By Charles Lane Poor. 



CONTENTS. 



Part I. Historical. 



Introductory Note 386 



Meridian Observations 386 



Von Lindenau 386 



Bianchi 387 



Secchi 387 



Hilfiker 387 



Discussion of Meridian Observations 388 



Auwers 388 



Newcomb and Holden 389 



Auwers 390 



Heliometer Measures 394 



Measures made in Connection with Transit of Venus 395 



Observations of Schur and Ambronn 396 



Part II. Photographic Measures. 



Rutherfurd Plates 403 



Northfield Plates 406 



Yerkes Plates, The Photo-heliometer 407 



Part III. Discussion of Observations and Results. 



The Figure of the Sun 409 



A New Tabulation of the German Heliometer Measures .... 409 



Tabulation of Results 413 



Conclusions 414 



Variabihty of the Sun's Diameter 415 



Fluctuations having the Same Period as the Sun-spots 416 



Search for Short Term Periodic Variations 418 



Part IV. Conclusions. 



385 



CD 



