DETERMINATION OF ASTRONOMICAL REFRACTION. 77 



with the meridian circle, will be recorded in a catalogue 

 that may be used for other purposes. The value of such a 

 catalogue will depend largely on the final methods adopted 

 in discussing the data, and publishing the investigation for 

 the benefit of future research work in other directions. 



No modern star catalogue is complete without appending 

 an investigation into the systematic corrections required 

 to reduce the observations to some acknowledged standard 

 or system, such as that of Newcomb, Boss, or Auwers. 

 An investigation of this nature is essential to define the 

 value of the whole work. In this connection Dr. Auwers 

 has perhaps done more than any other astronomer; through 

 his labours it is now possible to reduce the data of almost 

 every published star catalogue to a uniform system. 



The present paper, together with another on the " Lati- 

 tude of the Sydney Observatory," is preliminary to the 

 question of preparing a star catalogue to be issued from 

 the Sydney Observatory. 



My best thanks are due to Mr. Lenehan, f.r.a.s., the 

 Acting Government Astronomer, who kindly granted per- 

 mission to use the meridian circle to obtain the necessary 

 observations. I have also to thank Mr. Raymond, f.r.a.s., 

 together with Messrs. Olden and Oranney, officers of the 

 Observatory staff, for assistance in the observations and 

 reductions. 



2. Instrument. 

 The instrument, with which the observations were taken, 

 is the meridian circle of the Sydney Observatory. This 

 instrument was constructed by Messrs. Troughton and 

 Simms of London, and erected in its present position, during 

 the year 1875, by the then Government Astronomer, Mr. 

 H. 0. Russell, c.m.g., f.r.s. 1 A description of the instru- 



1 Retired from office 1905, February 28. 



