120 Winterhalter — Personal Equation Machine. 



the remaining columns give the personal equation with rates of 

 motion of the star corresponding, respectively, to 11° 21 /- 0, 

 60° 8'-5 and 80° 19'-0 decimation! 



The general deduction is : In the author's personal equation 

 a dependence is proved on the position of the telescope, i. e., 

 on the corresponding position of the body. 





Second 



Group. 







1. 





2. 



-15° 



45' 



— s 



•115 



+ 15 







— 



•096 



+ 59 



40 U. C. 



+ 



•017 



+ 82 



40 L. C. 



+ 



•463 



+ 59 



40 L. C. 



+ 



•040 



In this table, the first column gives the setting in declination 

 as read off on the circle, with an indication of upper and lower 

 culminations, the motion being, as stated, that of a star of that 

 declination ; the second column, the personal equation. 



The general deduction is : the amount of the personal equa- 

 tion is algebraically increased and changes sign (becoming posi- 

 tive) for slow motions ; this is also shown by the first group. 

 Besides, the second group indicates, although not as plainly as 

 the first, the dej^endence of the equation on the position of the 

 observer. 



The author finds also that in time his equation changes. For 

 a star of equatorial motion, it was found 



1886. Dec. 13-22 : —0 s -178; 



1887. May 23-27 : —0 -105; 

 • 1888. March 17 : +0 -148. 



A comparison of the two groups with results obtained in 

 Ley den in 1886 is interesting, but does not safely show a varia- 

 tion depending on varying positions of the telescope. 



Physiological investigations were not attempted nor were 

 generalizations for others, but the author draws two conclusions 

 applicable to his own case." 



The absolute personal error is with stars of a mean speed of 

 transit a minimum, increases with an increase and decrease of 

 the speed and, in the latter case, in general more rapidly than 

 in the former. 



The absolute personal error is, in general, dependent on the 

 position of the telescope and the requisite position of the body 

 of the observer, as also on the observed object, — star or limb. 



An ingenious disposition of the apparatus permitted the au- 

 thor to examine his personal error in observing the limb of 

 disks of various diameters. A brass ring was blackened and 



