OBSERVATIONS WITH THE ZENITH TELESCOPE. 



81 



33 from 19, 32 from 18, , 21 from 7, thus obtaining a series of values of the 



time required by the star to pass over the space measured by fourteen revolutions of the 

 screw. The difference between any value and the mean of all is the observed correction 

 on account of p, expressed in seconds of time. This must finally be converted into its 

 equivalent value in terms of revolutions of the screw. 



'Hie means of the differences SO found arc; given in the accompanying table, those for 

 51 Cephei having been reduced to the equivalent in terms of 5 Ursa; Minoris: 





Micrometer. 



ifi — ri"- 



Observed Difference. 



v. 



1 



19 - 33 



168 



— 3.90 



s 

 + .27 





a 



is 32 



— 140 



. — 3.25 



+ .22 





;{ 



17 — 31 



— 112 



— 2.55 



4- .23 





4 



16 — 30 



— 84 



— 2.21 



— .13 





5 



1 5 29 



— 5(1 



— 1.48 



— .09 





6 



14 — 28 



— 28 



— 1.11 



— .42 





7 

 s 



18 — 27 

 12 — 26 





 + 88 



— .03 



+ .08 



— .03 



4- .01 





'.) 



11 — 25 



+ 56 



+ 1.47 



— .08 



— .18 





10 



10 — 24 



+ 84 



+ 2.26 





11 



9 — 23 



+ 112 



+ 2.97 



— .19 





12 



8 — 22 



| 140 



-|- 3.35 



■4- 12 





13 



7 — 21 



+ I6S 



-1- 3.97 



4- 20 





The "observed difference" above is the observed value of p (ft 2 — ft' 2 ). 

 Therefore we have : 



p + ".02483 = .0001354 7^ 



wince on*; revolution A' represents the space traversed by the star in 57 8 .02. 



With this value of p we compute the corrections to the micrometer readings which 

 follow. These are expressed in terms of one revolution of the screw: 



Micrometer. 



Correction. 



Micrometer. 



Correction. 





7 & 33 



4- .0730 

 .0627 



14 & 26 



+ .0157 





8 32 



15 25 



.0109 





9 31 



.0527 



10 24 



.0070 





. 1 30 



.0435 



17 23 



.0039 





II 29 



.0353 



18 22 



.0017 





12 28 



.0279 



19 21 



.0004 





13 27 



.0213 



20 



.0000 



These corrections are applied to the micrometer readings and a preliminary reduc- 

 tion carried out employing an approximate value of the screw, as follows: 



Prom 1894, .1m.ii. 19 to July 25, I! 50".5352 



July 25 to Hit. 0, 50.5040 



Deo. to end of series, 50.5735 



