PREFACE. 



In March 1899, Dr. Keeler, late Director of the Lick 

 Observatory, suggested that I should undertake, for a thesis, 

 to reduce Professor Schaeberle's Meridian Circle obser- 

 vations for refraction, to discuss them completely, and to 

 end with the construction of tables for the Lick Observa- 

 tory. According to Astronomer Tucker, who is in charge 

 of the Meridian Circle work at the Lick Observatory, the 

 Pulkowa tables are not fully satisfactory for the reduction of 

 observations made there, and those of Bessel are still less so. 



After consultation with the late Professor Keeler, and 

 with his consent, it was decided to forego the reduction of 

 Professor Schaeberle's observations for the present, and to 

 determine the Constant of Refraction from observation? 1 

 be made by myself and to be reduced according to tue 

 method set forth in the following pages. 



I wish to express my thanks to our late Director, Professor 

 Keeler, for kind suggestions, for permission to use the 

 Meridian Circle, and for absolute freedom in the method of 

 procedure and in the reduction of the observations. 



Russell Tracy Crawford. 



University of California, 

 Berkeley, California. 



( 1 ) [ 103 ] May 5, 1903. 



