770 
DR. OLIVER LODGE OR ABERRATION PROBLEMS. 
Width of band of yellow light 
at first . 
when moving^ . 
O 
at last . . 
Displacement of middle band . ■[ right . 
L return on stopping 
156 
171i 
165 
divisions. 
J5 
9 
5 
3 ) 
3 3 
The highest estimate of this shift is xf 2 i^ds or say i^th of a band. 
The lowest estimate of this shift is xl^ths or say -^rd of a band. 
And these figures are within the limit of error certainly, the same as those given by 
the previous experiment with the spin reversed. 
Taking this experiment alone, therefore, one may say that reversing the rotation of 
the disks, from 21 revolutions a second one way, to 21 the other way, does not affect 
the virtual path of the light between them by so much as the 
— sV = 2 0 oth of a wave length, 
or even by so much as the 
= xoel'll of a wave length. 
Tested to see how many times the light was on this occasion going round the frame. 
Found that it was going only twice. Hence tlie length of path of each half beam was 
2X4X2 feet, since its path was approximately the periphery of a square two feet 
in the side. The whole path of the two beams is therefore 32 feet. A shift of a^th 
of a wave length in this length of path means a fraction 
X 6 X 10~‘ 
32 X 30 
= 3 X 10-10. 
The peiq^endicular distance of the average light path from the axis of rotation was 
1 foot, hence the effective speed of the disks either way was 277 X 21 feet per second, 
or say 260 feet a second altogether. 
(Compared with the speed of light this gives a fraction 
260 X 30 
3 X 1010 
2.6 X 10-k 
Comparing these two fractions we may conclude that the meaning of the above 
experiment is tliat the ether is not carried forward by the spinning disks with so 
much as g-^th of their velocity. 
