512 



Proceedings of the Royal Irish Academy. 



II. Chkonogeaphic Method. 



Power. 



F. Kaiser. 



P. J. Kaiser. 



Kara. 



van Hennekeler 



50 

 200 



- 0^-094 

 -0-067 



- 0^-096 

 -0 -051 



+ 0^-028 

 - -029 



- 0^074 



- -084 



Power. 



Plantamour. 



R. Wolf. 



Hirsch. 



70 

 200 



- 0^-063 



- -039 



- 0^-243 

 -0-170 



- 0^-154 

 -0 -134 



We see from this that the changes (if such appear at all) are very" 

 small, and there does not seem to exist any law, as it would probably 

 be too early to say that a higher power decreases the error, consider- 

 ing the small number of cases. 



With respect to the influence of the declination, there cannot at 

 the present moment be said anything in general, as this important 

 question has been very little examined. In itself, it is very impro- 

 bable that personal equations should vary much according to the 

 declination of the stars, as only the difference between the two 

 observers' dependence could be visible. And there is no reason to 

 expect that a personal error, generally, should vary regularly according 

 to the apparent velocity of the star, as even in rather high cleclinations 

 (50° or 60°) the space passed through by the star in a second is large 

 enough to be divided with certainty. And that the error should in- 

 crease with sec 8, as R. "Wolf thinks has been found by the observa- 

 tions in Ziirich,^" does not necessarily result from them, and is besides 

 very improbable, as personal errors must arise from faults in the 

 sight, or in the hearing, or in the co-operation of these senses, and 

 in the chronographic method, from faults in the pressing of the key. 

 Faults of the latter kind, or in the hearing, must necessarily be the- 

 same everywhere ; while faults in the sight, as already said, can 

 hardly change until in very high declinations. C. Wolf's observations 

 show certainly a regular but very small variation of the error, as the 



* Astron. Mittheilungcn, xxv. (Yierteljalirssclirift der Gesellschaft in Ziiiich,.. 

 xiv.), 1869, p. 265. 



