622 PROFESSOR CHALLIS'S OBSERVATIONS OF THE 



made. It is proper on each occasion of using it to determine the index errors by observations 

 of stars. 



I proceed now to give the observations just as they were set down in the memorandum-book, 

 inchisive of those for index errors, premising only that the instrumental azimuths are reckoned 

 from East towards Soiith, and that the noted times were taken from a solar chronometer, which by 

 a comparison with the transit clock immediately after the observations was found to be 1". 52'. 

 fast on Greenwich Mean Time. 



(1) S*". 49". 0^ Corona 1" South and 1° East of /3 Andromedae. 



(2) 8.51 .0 1;^" South and f 



(3) 8.55 .0 1° South and J" 



(4) 9- 1-40 2l° South and l^" 



(5) 9. 4.25 3" South and 2° 



(6) 9. 9 . Altitude of Corona by Meteoroscope 68". u' Azimuth 43". 44' 



(7) 9.10.23 /3 Andromeda; 73.15 59.58 



(8) 9.13.15 Corona 67- 4 37.56 



(9) 9.19.20 Corona 71.47 42.28 



(10) 9,29.12 /3 Andromedae 72.20 77-10 



(11) 9.32. Corona l" South, and i" East of (i Trianguli. 



(12) 9.35.15 Altitude of Corona by Meteoroscope 69 . 20 Azimuth 37.24 



(13) 9.44.10 Corona 68.55 41.21 



(14) 9.49.40 /BAndromedas 71.20 84.47 



(15) 9.56. Corona 2" South, and 1^° East of ji Trianguli 



(16) 10.6.0 2" South, and 3" 



(17) 10.10.11 Altitude of Corona by Meteoroscope 69.28 Azimuth 42.12 



(18) 10.14.36 /3 Trianguli 72. 5 65.30 



(19) 10.20.30 Corona 69.30 51. 



(20) 10.23. 5 Corona 70.28 40. 



(21) 11. 6.20 Corona 71. 62 . .S5 



(22) 11.10.56 Corona 69.5 55.30 



(23) 11.12.50 Corona 70.55 52. 4 



(24) 11.14.10 Corona 69.50- 47. 6 



(25) 11 .16. The star ^ Persei appears in the middle of the Corona. 



(26) 11.17.30 Altitude of Corona by Meteoroscope 67.30 Azimuth 49.40 



r ^Persei 69. 10 46.14 



^'' I The Corona seemed coincident with ^ Persei 



(28) 11.26. Altitude of Corona by Meteoroscope 70.10 Azimuth 43. 6 



Of the above observations Nos. (19) and (21) were marked 'doubtful.' Nos. (23) and (26) 

 were reckoned good. 



The position of the Corona was calculated from these observations in the following manner. 

 When the observation was made by reference to a star, from the noted time corrected for error of 

 the chronometer, and the known longitude of the place of observation (viz. 23',5 East), the sidereal 

 time was calculated in the usual way, and then from the known Right Ascension of the Star, the 

 hour angle (A) Eastward was deduced. The co-latitude of the Observatory (viz. 37° . 47') being 

 represented by X, and ^ being the North Polar distance of the Star, its distance (m) from the 

 meridian, and its distance («) from the astronomical zenith, were calculated by the following 

 formula; : 



sin TO = sin ^ sin h, tan (p = tan o cos /(, cos z = cos (0 - X) cos in. 



Let ,u and T represent the estimated distances of the Corona from the star Eastward and South- 



