W. A. Rogers on Variability of Personal Equation. 299 
hate swing of the pendulum gives the constant spaces wr, 
discussion after numerous and careful measurements upon dif- 
4 ferent parts of the scale, is ‘77*+'015s. He 
‘Interval between the beginning of the automatic break and 
_ that made by the observer is less than “77° the observation is 
too early, and when greater, it is too late. The difference, 
either way, is the absolute personal equation. If there are two 
observers, their relative personal equation is easily found, from 
the absolute equation of each. 
In entering upon this discussion the first and the main ques- 
nis: 
tio 
Does the personal equation vary from any cause ? 
As the basis of investigation, I give below the mean of the 
Values found for each date, with explanatory remarks concern- 
ing the conditions under which the observations were made. 
3y an abnormal position of the body, I mean as painful a posi- 
tion as I could assume. The wires were illuminated by placing 
alight nearly in front of them. Faint illumination was pro- 
_ uced by reducing the volume of the flame. 
The observations were made by Prof. Edward M. Tomlinson, 
Mr. Herbert E. Babcock, and myself. 
* 
i Absolute Personal Equation. 
Roaers. 
Pate, Equation. Ranerki Date. Equation. Remarks. 
1 oy. Nov. 
I=—-1185 29 +-017—Read up all the preceding 
0 records. ee 
: 93 
21 *057—Read the record for Nov. 19|Dec. 
E —-067 Normal position. 
z 022 and20. Firstknowledge of! 5 
23-088 the value of my personal| 6 | °032 Abnormal position. 
- —047 equation. Observationsfrom| 6 _ -038 Normal. 
+025 Noy. 19 to Nov. 29 were| 6 ‘037 Abnormal. 
‘019 made under a normal condi-| 7 “042 Normal. 
034 tion of the body. 7 ‘040 Abnormal. 
019 8 042 Normal. — 
