634 Proceedings of the Royal /Society 
the telephone. Fine iron wire answers very well, but in this case it is 
inapplicable, as it sets up a clearly audible action on its own account. 
When the ear is now applied to the telephone the ticking that you 
would hear in the wire, if it were straight, is heard distinctly, and 
is the only distinct sound, for the up and down motion of the 
convolution only produces a slight jingling in the connecting 
wire, and possibly also in the coil. When the convolution is held 
tight in the fingers the ticking goes on if anything more distinctly 
than before. Whether the mechanical motion by the increased 
fixity of the helix is converted into louder ticking, could not be 
decided by the difference. Here we have two vibrations quite 
distinct from one another, the ticking in the wire and the me- 
chanical motion due to the mutual electro-magnetic action between 
the rod and the coil. If this last were quick enough it would 
also be telephoned, but the rate of vibration being below that of 
musical frequency it is nothing but inaudible motion. In this 
helix action I would submit we have a dissected view of all 
receiving telephonic action — a vibration in the body clearly of 
molecular origin, and another of the body of a push-and-pull kind. 
The latter may be stopped or nearly so, but not the former. From 
its internal origin it is bound to make itself good, and when the 
body is held in the grasp of the most rigid substance it only propa- 
gates in it the minute vibrations which no elastic matter can stop. 
In the vibrations of coils, cores, or plates, the same thing holds. 
Molecular vibration is present in them all, and how far mechanical 
vibration chimes in in unison depends entirely on the ease with 
which such can be produced. 
There is apparently a marked difference between these two vibra- 
tions. The one can make itself good acoustically by one impulse, 
the other not. I have tried in vain, while holding taut the 
thread of a mechanical telephone without letting the fingers slip, to 
produce, by a sudden pull or let go, the tick that resounds in iron 
or a conductor when a current suddenly begin or ends, and I could 
only do so by letting the string slip the slightest degree, so as to set 
up a short series of vibrations. Each galvanic or magnetic tick or 
tap may not, in the first instance, be more than a simple shock ; 
but so sudden is it that the particles concerned do not recover at 
once, but continue vibrating for an infinitesimal time, and hence 
