STARS IN COMA BERENICES. 



425 



stars and the readings on the central taken on the same day, 

 we may, without affecting the final results, subtract a constant 

 from the screw correction. Taking, then, the zero point at gR, 

 and as our argument tenths of millimeters (or fifths of a revolu- 

 tion) beyond gR, we get the following table for correcting the 

 readings of the horizontal screw : 



Reading of Head. 



Corresp. }im. 



Corresp. Correction, 



9.0 



0.0 



0000 



9.2 



0.1 



— O.OOOI 



9-4 



0.2 



— 0.0002 



9.6 



03 



— 0.0003 



9.8 



0.4 



— 0. 0004 



10.0 



o.S 



— 0.0005 



10.2 



0.6 



— 0.0006 



10.4 



0.7 



— 0.0007 



10.6 



0.8 



— 0.0008 



10.8 



0.9 



— 0.0009 



II. 



I.O 



O.OOIO 



During the second half of a day's work, the initial setting on 

 the star was usually 9. 5^^. As a result, the readings on the 

 scale sometimes fell beyond i\R. For such cases the above 

 table will no longer apply as it stands, for the correction beyond 

 I iR does not bear the same proportion to ^ in as holds below 

 that point. We may, however, construct a table similar to the 

 preceding, but differing in the last figures. For, all the stars 

 being again measured beginning always at the same point on 

 the screw, we may, as before, subtract a constant from the screw 

 correctioiis. We obtain thus the table : 



Reading of Head. 



Corresponding 



% m 



Corresponding Correction. 



9-5 







0.0 







— 0. 0000 



9-7 







0.1 







—O.OOOI 



9-9 







0.2 







— 0.0002 



10. 1 







0-3 







— 0.0003 



10.3 







0.4 







— 0. 0004 



10.5 







0-5 







— 0.0005 



10.7 







■ 06 







- — 0. C006 



10.9 







0.7 







— 0.0007 



II. I 







o.S 







— 0. 00074 



II-3 







0.9 







— 0.00072 



II. 5 







1.0 







— 0.00070 



Annals N. Y. 



Acad. 



Sci., 



, XII, April 3, 

 (85) 



1900 — 27. 



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