49° Mr. Cavendish's Experiments to determine 
the last experiment, the case was different ; for though, on 
moving the weights from positive to negative, the effect seemed 
to increase on standing, yet, on moving them from negative to 
positive, it diminished. 
My next trials were, to see whether this effect was owing to 
magnetism. Now, as it happened, the case in which the arm was 
inclosed, was placed nearly parallel to the magnetic east and 
west, and therefore,- if there was any thing magnetic in the 
bahs and weights, the balls would acquire polarity from the 
earth ; and the weights also, after having remained some time, 
either in the positive or negative position, would acquire po- 
larity in the same direction, and would attract the balls ; but, 
when the weights were moved to the contrary position, that 
pole which before pointed to the north, would point to the south, 
and would repel the ball it was approached to ; but yet, as re- 
pelling one ball towards the south has the same effect on the 
arm as attracting the other towards the north, this would have 
no effect on the position of the arm. After some time, how- 
ever, the poles of the weight would be reversed, and would 
begin to attract the balls, and would therefore produce the 
same kind of effect as was actually observed. , 
lo try whether this was the case, I detached the weights** 
from the upper part of the copper rods by which they were 
suspended, but still retained the lower joint, namejy, that 
which passed through them ; I then fixed them in tjfeir posi- 
tive position, in such manner, that they could turn round on 
this joint, as a vertical axis. I also made an apparatus, by which 
I could turn them half way round, on these vertical axes, with- 
out opening the door of the room. 
Having suffered the apparatus to remain in this manner for 
