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CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D ser. 



could have been made. In these cases the readings have 

 been reduced to the meridian. , 



For the position of the circle four microscopes were read. 

 Settings were made upon two scratches under every micro- 

 scope. The circle microscopes were usually read after the 

 star had been bisected. In a few cases, because of a 

 following star culminating very soon, the microscopes were 

 read before the bisection. In such cases the position of the 

 circle was quickly checked after the bisection. 



The correction for runs for a night was obtained from all 

 of the microscope readings of the night. This correction 

 has been applied to all of the observations. Its values for 

 the several nights of observing are given in the following 

 table : — 



These corrections were applied to the circle readings to 

 reduce them to the mean position of the two scratches; so 

 that for a reading of o" the correction is -j-R, for 60" it is o, 

 and for 120" it is — R. 



In the few cases where the bisections were made a little 

 late the reductions to the meridian were computed from the 



formula, 



sin 2 I (r— m) . , 



— : - sin 20 



sin 1 



The horizontal flexure in this instrument is very small. 

 In his work published in Vol. IV, " Publications of the Lick 

 Observatory," Astronomer Tucker adopts the correction 

 o".isin Z. D., which was determined from a series of 

 observations extending over two and a half years. In this 

 work but two observations for flexure were made, one on 

 1899 June 3, and the other, 1899 July 8. The mean of 



