624 
Proceedings of the Royal Society 
striking and lifting motions, no visible deflection is got, though 
the same taps on the disc of a Bell telephone make deflections of 
from 5 to 10 mm. of the scale. When the disc is taken off, we 
may ascertain the efficacy of vibrations in the line of the plate to 
generate currents. Taking a small thin iron rod and giving it small 
vertical excursions, I found that when these were made in the line 
of the plate no effect whatever was got when the rod was held 
equatorially to the line of poles, but that as the rod was brought to 
either pole an increasingly slight effect was seen. This might be 
due in part or perhaps wholly to the want of parallelism of the 
motion to the pins, for the slightest side or horizontal motion pro- 
duced a marked effect. That even this stiff plate vibrates when 
spoken to there can be little doubt, but the vibrations cannot, on the 
ordinary push-and-pull principle, push and pull at right angles to 
themselves. The action of the disc may be due to the blow it gives 
to the pole pins as an ordinary resonator, and possibly also the action 
of blows just hinted at may be present. The aerial blows may 
directly induce currents, or they may do so in altering the shape of 
the plate by vibration. However this may be, the problem may 
safely crave a solution from the push-and-pull theorists. When 
the plate is not screwed down, but laid or gently pressed on the pins, 
and more especially if it be made the bottom of a shallow tin box 
with a hole on the top, its performance almost rivals that of Bell’s 
telephone. The improved effect is no doubt due to facility of vibra- 
tion which is as necessary to the sounding power of vibrations of 
molecular origin as to those produced mechanically. 
I made an attempt also to see whether the coil itself had any 
sounding action. If a blow can make soft iron induce a current, 
possibly a closed coil, the electric analogue of soft iron, may do so 
under the same treatment. I first tried this by hitting the side of 
a coil by a small wooden hammer, then as the frame of it gave way 
under this usage, I cemented it to a piece of board and hit the board ; 
but as again the whole coil split up under the blow's, I lastly tied 
it to a strip of wood, and used it as the head of a hammer against 
the end of a wooden rod. In each case I succeeded once or twice 
in telephoning the taps, but most unaccountably, for I might tap 
ever so hard and so often afterwards without being again so fortunate. 
How the sounds were sent in these cases I cannot say. The coils 
