WITH A FOURTEEN FEET REFLECTOR. 



185 



their logarithms to two places tabulated. Its application to each individual 

 measure thus becomes very easy. 



25. The first column of the following series of measures contains the date of 

 observation. In the second are the numbers of the measured stars, as referred 

 to the catalogue. The sign — between them indicates differences of right as- 

 cension or declination; thus, in Art. 26, 1 — 9 stands for Decl. of star (1) — 

 Decl. of star (9.) 



The third column contains the ofoerwec/ difference ot right ascension (A',) or 

 of declination of (D'.) The fourth shows the altitude or sidereal time of ob- 

 servation. In the fifth is the correction for refraction due to such altitude, for 

 declination r D' cosl v, and for right ascension 2 r D' sin. v cos. v sec. ^, ac- 

 cording to the formulae above given. By the addition of this correction to the 

 observed differences in the third column we are furnished in the sixth with 

 the true differences, (A) and (D.) The seventh column contains the number 

 of measures, of which the observed difference in the third column is the mean, 

 and the eighth shows the probable error of each single measure, or the average 

 difference from the mean of the set; these are respectively designated by n 

 and e. 



Nebula h. 1991. 

 26. Differences of Declination. 



Date. 



Stars. 



D' 



Altitude. 



Correction 

 for Kefr. 



D 



n 



c 



Remarks. 



Oct. 



3 



1 — 9 



+ 905".4 



19".. .18° 



-f- 2".0 



-f 907".4 



4 



I". 2 



-Very liable to be affected by slight 



li 



10 



a 



905 .4 



13 



3 .4 



908 .8 



4 



.4 



errors in pos. of wires. 



Nov. 



2 



t( 



897.6 



8I..7..6..5 



9 .5 



907 .1 



13 



2 .5 



-Low, but clear. 



i( 



4 



<( 



899 .9 



10 ... 6 



7 .4 



907 .3 



15 



1 .3 





Oct. 



5 



2 — 9 



216 .0 



17 ...16 



.6 



216 .6 



6 



2 .2 





(1 



8 



(( 



-f- 215 .6 



15 ...14 



+ .7 



-1- 216 .3 



8 



.7 





<( 



5 



8 — 9 



— 8.1 



no 



corr. 



— 8 .1 



6 



.8 





a 



8 



u 



— 9.6 



no 



corr. 



— 9 .6 



8 



.7 





a 



4 



19 — 9 



+ 00 .4 



20 ...19 



-FO.l 



-f- 60 .5 



9 



4 .4-Star (19) invisible near the wire. 



<< 



8 



(.i 



65 .9 



17 ...16 



.2 



66 .1 



8 



2 .0-Wire made as faint as possible; 



(< 



5 



21—9 



240 .0 



19. ..18 



.5 



240 .5 



6 



0.5 



measures decidedly better on 



<' 



8 



(( 



237 .7 



13 ...11 



1 .0 



238 .7 



8 



.5 



this account. 



(( 



1 



22 — 9 



447 .9 



18 ...16 



1 .1 



449 .0 



3 



1 .5 





<( 



3 



(( 



449 .5 



21 



.8 



450 .3 



2 



.7 





n 



10 



4( 



+ 450 .8 



15 ...14 



+ 1.4 



+ 452 .2 



8 



.4 





(( 



9 



24 — 9 



— 70 .2 



20 ...18 



— .2 



_ 70 .4 



6 



3.0 



-Excessively difficult to measure. 



(( 



4 



25 — 9 



-f 112 .4 



19 ...17 



+ .3 



+ 112 .7 



8 



2 .5, Probably not very accurate. 



(( 



8 



-1- 112 .5 



20 ...17 



-1- .3 



+ 112 .8 



9 



1 .2-Wire made faintly visible; this 



(( 



9 28 — 9 



— 270 .2 



22 ...20 



— .5 — 270 .7 



9 



.6 certainly adds to accuracy. 



VII. — 2 w 



