COMET OF 1 889-1 896-1 903 253 



These differences in declination would indicate that the point 

 of the comet, which was used in measuring its position, was a 

 little to the south in the first appearance and a little to the north 

 in the second appearance of the mean position as indicated by a 

 least square solution of all the observations. Apparently the 

 observed nucleus was a little more than 2" farther north than, by 

 theory, it should have been in the second appearance. A large 

 portion of this discrepancy, however, can be accounted for by a 

 simple investigation of the observations upon which this determi- 

 nation rests and of the method of weighting such observations. 



If the observations be compared with the corrected ephemeris 

 and the differences between the observed and computed places 

 for each separate observation formed, it will be found that the 

 observations of each observer are affected by a systematic 

 error. The observers at Denver and Cordoba invariably placed 

 the comet a little north of the place assigned by the observers 

 at Mt. Hamilton and Washington. The mean of 34 observa- 

 tions made with the 36-inch at Mt. Hamilton differs from the 

 ephemeris place by — o^.q, while the mean of 12 observations 

 made at Cordoba differs from the ephemeris by -f 4''. 3, and the 

 mean of 47 observations at Denver differs by + 2^.4. Further, 

 in the case of the Mt. Hamilton observations the individual dif- 

 ferences are somewhat equally divided as to sign, 15 being posi- 

 tive and 19 negative ; of the Cordoba observations, on the 

 other hand, 1 1 are positive aud only i is negative. Thus at 

 Cordoba the comet was always estimated as about 5" north and 

 at Denver about 3" north of the position assigned to it by the 

 observers at Mt. Hamilton. 



Although the observations at Denver and Cordoba were 

 given much less weight than those of Mt. Hamilton, yet it is 

 evident that a normal place depending entirely on Denver ob- 

 servations would place the comet some 3" north of a normal 

 place depending upon Mt. Hamilton observations solely ; and a 



