DR. OLIVER LODGE ON ABERRATION PROBLEMS. 
769 
This time the tremors which still occurred at about 800,1000, and 1150 revolutions 
did not seem to produce much effect. 
The following were the readings; each wire read on its own micrometer head. 
X-wire, set on 
yellow of first band 
Vertical wire, set 
in middle of middle 
to left. 
band. 
At rest . . ■. 
At 800, no shift of middle band 
At 1000, barely any 
7 
60 
At 1260 revs., set again and read .... 
11-5 
68 
Stopped. Set again and read. 
11-5 
64 
To carry the vertical wire from its position 64 into coincidence with the X? 
required a motion of 154 divisions (viz., about one revolution and a half of its 
micrometer screw). 
The experiment was satisfactory. Its result was 
at first . 
Width of a band of yellow light < 
when moving . 
at last . 
Displacement of middle band . 
r shift to right . 
\ return on stopping . 
146 divisions. 
158 
154 
8 
4 
55 
The highest estimate of this shift is, therefore, yf-g-ths, or say -^th of a band. 
The lowest estimate is yfyths, or say s^th of a band. 
Then reversed the brushes and immediately took another satisfactory observation. 
Third Spin. —Direction reversed, that is, so as to help the transmitted beam. 
X-wire set on yellow 
of 1st band to left. 
Vertical wire set on 
centre of middle 
white band. 
At rest. 
No shift at 800 or 900. Tremor at 1000 
9 
69 
Set at 1250 and read. 
15-5 
78 
Stopped and set again. 
14 
73 
To carry the vertical wire from 73 up to the \ 2 dj needed 165 divisions. The 
result of this was 
5 F 
MDCCCXCIII.—A. 
