WA. Rogers on Variability of sors Equation. 301 
Feb. 10—-+ °0368 Junel5 +° oays Nov. 29 —°030* 
10 iz *055 Feb, 10 
Apr. 27 +°047 22 "032 10 "143 
May 31 "062 26 036 Apr. 27 071 
June 2 034 27 +°047 27 —137 
4 0 
9 +070 
Relative Personal Equation. 
ROGERS minus TOMLINSON= RoGERS minus BABcock= 
— R—B. 
Nov, 19——°214° Apr. 27-8==—"098° Nov. 22=-—"112" 
20 *209 May 31 "113 23 . 
21 -163 31 "102 24 —040 
22 161 31 "081 25 +°025 
23 "255 June 2 079 26 +°008 
24 “196 2 "053 27 016 
25 "155 2 068 29 +°047 
26 "185 2 079 Feb. 10 —'040. 
a7 "145 4 08 0 +076 
28 144 4 094 Apr. 27-8 °031 
29° 196 4 081 27-8-+-026 
Feb. 10 ‘lll 9 "103 27-8— 006 
10 030 15 061 
Apr. 27-8 °087 15 065 
27-8 ‘092 17 110 
27-8 124 22 “085 
27-8 -116 26 “081 
27-8 +096 26 082 
27-8 ‘088 26 °055 
27-8 -076 27-8 055 
27-8 ‘080 27-8 "O75 
27-8 ‘098 27-8 —087 
27-8—'058 
It will be evident from an examination of the values given 
above, Sat personal equation is a varying quantity, if it can be 
shown that the variation exceeds the probable error of observ- 
ation. Without going into details, I give below the value of 
the probable error from each source, , depending upon a suffi- 
ciently large number of observations 
L Probable error of observation for ck star— 
ten revolutions, R=+'013* 
Il. Probable error of each reading on the scale sani sh 
Til. Total error derived from a change in the 
common unit of measurement as affected - 
by a variable beat of the chronograph 
pendulum, (estimated), —=+'02 
