516 



Proceedings of the Royal Irish Academy. 



1871. IToTiox Eeteogeade.* 



log. sec. . 



s. 



Error b}- 

 E3'e and Ear. 



Error bj' 

 CbronogT. 



Xumber 

 of Obser- 

 vations. 



Chr.— EE. 



EE. + Chr. 



2 



0-06 

 0-41 

 0-67 

 1-15 

 1-50 

 1-77 



29'^26' 

 67 6 

 77 39 

 85 57 



88 11 



89 2 



- O^-Ooo 



- 0-28 



- 0-001 

 + 0-04 

 + 0-14 

 + 0-46 



- 0^-061 



- -085 

 -0-112 



- -28 

 -0-32 

 -0-02 



7 

 8-9 



8 

 7-61 



8 



8 



- 0^ 006 

 -0-057 

 -0-111 



- 0-32 

 -0-46 

 -0-48 



- 0^-053 



- -057 



- -056 

 -0-14 

 -0-03 

 + -22 



II. "Wagner considers these results worthy of some credit, as the 

 difFerenees betTveen his registered transits, f and those obseiTed with 

 eye and ear, agree very well with what has appeared from his observa- 

 tions of the real stars. The constant faults (caused by defects in the 

 apparatus) can, for equatorial velocity, only amount to a few thou- 

 sandths of a second ; for the slowest motion, they may be considerably 

 larger, on account of faults in the adjusting screws, but the mean 

 results contained in the last column of the above table may, notwith- 

 standing this, be considered as a very fair approximation to the 

 truth. 



The last question we now have to answer is, has the apparent 

 brilliancy of the objects observed any influence on an observer's esti- 

 mation of its transit? That a personality is distinctly visible in 

 observations of the first and second Kmbs of the sun or the moon, has 

 lately been shown by ^'. Dunkin, in Greenwich, in two papers laid 

 before the Royal Astronomical Society, :J: the personal eiTors being 

 detected in the tabular errors of the E,. A. of the moon and of the sun. 

 The different habits of observing these two celestial objects by the 

 foui' piincipal observers in Greenwich, are essentially the same in the 

 observations of both of them, as the following table shows :§ — 



* Corresponding to tHe direction of the motion of a star between the Pole and 

 the Zenith. 



t To he found in the column headed : " Chr. — EE." 



X On Personality in observing Transits of the limbs of the Moon — "ilonthly 

 !N'otices," Yol. xxix., p. 259. On Personality ia obsei-ving Transits of the first and 

 second limbs of the Sun. — Ibid., xxxv., p. 91. 



§ For the moon Mr. Dunkin has not only used the observations taken with the 

 transit -instrument (quoted here), but also those taken with the altazimuth, which, 

 upon the whole, give similar results, although made ujider quite different circum- 

 stances. 



