by
the iron or steel diaphragm of the telephone, both as regards the nature
of the movements that it effects through elasticity and the conversion of
mechanical into magnetic energy as a result of its motions.

I. When we produce simple or complex vibratory motions in the air in
front of the diaphragm, like those that result from articulate speech,
either the fundamental and harmonic sounds of the diaphragm are not
produced, or else they play but a secondary _role_.

(1.) In fact, diaphragms are never set in vibration, as is supposed, when
we desire to determine the series of harmonics and nodal lines, since we
do not leave them to themselves until they have been set in motion, and
we do not allow a free play to the action of elastic forces; in a word,
the vibrations that they are capable of effecting are constantly _forced_
ones.

(2.) When a disk is set into a groove, and its edges are fixed, theory
indicates that the first harmonics of the free disk should only rise a
little. Let us take steel disks 4 inches in diameter and but 0.08 inch in
thickness, and of which the fundamental sound in a free state is about
_ut_{5}_, and which the setting only further increases. It is impossible
to see how this fundamental and the harmonics can be set in play when a
continuous series of sounds or accords below _ut_{5}_, are produced
before the disk; and yet these sounds are produced perfectly (with feeble
intensity, it is true, in an ordinary telephone) with their pitch and
quality. They produce, then, in the transmitting diaphragm other motions
than those of the fundamental sound and of its peculiar harmonics.

(3.) It is true that in practice the edges of the telephone diaphragm are
in nowise fixed, but merely set into a groove, or rather clamped between
wooden or metallic rings, whose mass is comparable to their own; and they
are, therefore, as regards elasticity, in an ill ascertained state. Yet a
diaphragm of the usual diameter (from 2 to 4 inches), and very thin (from
0.001 to 0.02 inch), clamped in this way by its edges, is capable of
vibrating when a continuous series of sounds are produced near it, by
means, for example, of a series of organ pipes. But the series of sounds
that it clearly re-enforces, in exhibiting a kind of complex nodal lines,
is plainly _discontinuous_; and how, therefore, would the existence of
such series suffice to explain the production of a _continuous_ scale of
isolated or superposed sounds, t