621 
of Edinburgh, Session 1877-78. 
to rotation in this case can hardly he looked upon as such. To 
exclude this cause, I put the coils in the best position for 
generating such currents, and connected them with a moderately 
sensitive reflecting galvanometer. I inserted a piece of wood 
between the prongs, and wedge-like drove them suddenly out, 
and allowed them to return, keeping time with the known 
pendulum-like oscillation of the mirror so as to accumulate effect, 
but no result was got. Again it might be that the coils, tightly 
as they were wound, were yielding, and we had only a case of 
shaking a coil in front of a magnet, instead of a magnet in front of 
it. That this was not the case was proved by cementing the coils to 
the sides of the prongs at right angles to the direction of motion, and 
though the forks vibrated almost unmusically with such protube- 
rances, yet what sound they emitted was telegraphed to the listener. 
The most likely cause was that the coils were fixed as regarded the 
prongs on which they were stuck, but were affected by the distant 
prong which vibrated in front of them. The sounds of the vibrat- 
ing coils were louder than when the coils were fixed, and the other 
prongs vibrated at the same distance ; but that might be accounted 
for by the fact that the prong to which the coil was fixed was an 
active agent in propagating the vibrations of its companion prong 
to its own coil. The only chance of anything like internal action 
being heard here rests on the possibility that this last is not 
sufficient, and that is certainly a slender enough basis to bufld a 
theory upon. 
In pursuit of the same internal sending action, I cemented two 
coils, one to the end, the other to the middle of a bar magnet. 
Both transmitted telephonic currents when the magnet was struck, 
the end one much louder than the other. Again, an unmagnetised 
tuning-fork was made to vibrate above a coil, and its note was feebly 
yet distinctly heard at the listening end. To test wdiether it and 
the other objects afterwards mentioned were magnetised, I brought 
them near a small active magnet about an inch in length, and 
before another much heavier, 9 inches in length, and watched to see 
if repulsion or even indifference was shown to any part of them ; 
and lastly, I made them vibrate in front of the coil connected with 
the reflecting galvanometer in the position in which their sending 
action was afterwards tested. These tests cannot be alleged to prove 
VOL. ix. 4 N 
