DETERMINATION OF THE CONSTANT OF REFRACTION 



FROM OBSERVATIONS MADE WITH THE 



REPSOLD MERIDIAN CIRCLE OF THE 



LICK OBSERVATORY. 



BY RUSSELL TRACY CRAWFORD. 



CONTENTS. 



Page. 



Introduction 105 



/. The Meridian Circle 105 



2. The Room 107 



3. Meteorology 108 



4. Plan for Observing 114 



Observations 118 



/. List 118 



2. Details of Observations 119 



3. Reduction of Observations 122 



4. The Constant of Refraction 190 



3 . Latitude , 191 



Conclusion 192 



Addendum 193 



Introduction. 



/. The Meridian Circle. — The instrument with which 

 these observations for refraction were made has been fully 

 described by Astronomer Tucker in Volume IV of the 

 " Publications of the Lick Observatory, 1900." For the 

 sake of completeness, however, it will be described again 

 in this paper. 



The instrument was made by Messrs. Repsold and Sons, 

 and was described by Professors Auwers and Krueger to be 

 " in its construction in every way suited to be the chief 

 instrument in an observatory of the first class." (cf. Vol. I, 

 " Publications of the Lick Observatory.") 



The aperture of the object glass, which was made by 



Clark and Sons, is 6.4 inches. Its focal length is 6 feet 



[105] 



