88 
Proceedings of the Boyal Society 
Details of Experiments. 
The first experiments were made in 1873, March 28, and 
they were continued regularly until April 16. The rod of flint- 
glass was suspended in air, water, and oil. A rotation was nearly 
always communicated to the rod when contact was made with the 
electro-magnet. When the magnetism of the electro-magnet was 
reversed I sometimes got a rotation in the opposite direction, and 
sometimes a rotation in the same direction, but to a different 
extent. The apparatus was repeatedly dismounted and set up 
again with all the parts changed. The effects were generally 
unaltered. In noting the experiments, I used the terms “no 
contact,” “right contact,” and “left contact,” as being least liable 
to lead to error. “ No contact ” means that the circuit was broken. 
“ Right contact ” means that the lower pole of the electro-magnet 
would, if free, point to the north. “ Left contact ” means that the 
lower pole of the magnet would, if free, point to the south. When 
the readings of the scale are increasing the glass is rotating in the 
direction of the hands of a watch with the face upwards. The 
glass was sometimes put into water or oil, and in this case also 
rotation was generally observed. 
The rotation oscillations in air were so great as to necessitate 
reading the scale at the end of each half oscillation, and taking a 
mean. In the following table each reading is a mean of many 
observations : — 
March 29. — Flint-Glass in Air. 
No contact, . 
245 scale reading. 
Means. 
Right „ 
155 
L = 146, 
Left „ 
146 
R = 155. 
No „ . , 
235 
N = 240. 
Flint-Glass in Water. 
No contact, . 
415 
Right „ 
268 
L = 
248. 
Left ,, 
248 
R - 
268. 
No „ 
410 
N = 
412. 
