61 



Arcturus. 



In deducing these results from the observations of Arcturus, 

 the annual change of N. P. D. has been taken = +16",81. The 

 annual proper motion of Arcturus may be considered in some 

 measure uncertain, and it may be thought that the conclusi>)n 

 respecting parallax will be affected thereby. But this is not the 

 case. Let the annual variation in JV. P. D. = I8",81+e. * 



Then the mean of the above 42 observations gives 

 the mean zenith distance = 33' 12' 55", 11 — ,54/> — ,4:e. 



* The annual variation in N. P. D. of Arcturus seems by my observations to be at least 

 + 19",1. But the interval since they commenced is too short to speak with much conSdence. 



