A' in such a manner that it should copy the
motion of the reed A, in which case its movements would occasion a sound
from the membrane _n'_ similar in _timbre_ to that which had occasioned
the original vibration.

[Illustration: Fig. 7]

[Illustration: Fig. 8]

The results, however, were unsatisfactory and discouraging. My friend,
Mr. Thomas A. Watson, who assisted me in this first experiment, declared
that he heard a faint sound proceed from the telephone at his end of the
circuit, but I was unable to verify his assertion. After many
experiments, attended by the same only partially successful results, I
determined to reduce the size and weight of the spring as much as
possible. For this purpose I glued a piece of clock spring about the
size and shape of my thumb nail, firmly to the centre of the diaphragm,
and had a similar instrument at the other end (Fig. 8); we were then
enabled to obtain distinctly audible effects. I remember an experiment
made with this telephone, which at the time gave me great satisfaction
and delight. One of the telephones was placed in my lecture room in the
Boston University, and the other in the basement of the adjoining
building. One of my students repaired to the distant telephone to
observe the effects of articulate speech, while I uttered the sentence,
"Do you understand what I say?" into the telephone placed in the lecture
hall. To my delight an answer was returned through the instrument
itself, articulate sounds proceeded from the steel spring attached to
the membrane, and I heard the sentence, "Yes, I understand you
perfectly." It is a mistake, however, to suppose that the articulation
was by any means perfect, and expectancy no doubt had a great deal to do
with my recognition of the sentence; still, the articulation was there,
and I recognized the fact that the indistinctness was entirely due to
the imperfection of the instrument. I will not trouble you by detailing
the various stages through which the apparatus passed, but shall merely
say that after a time I produced the form of instrument shown in Fig. 9,
which served very well as a receiving telephone. In this condition my
invention was, in 1876, exhibited at the Centennial Exhibition in
Philadelphia. The telephone shown in Fig. 8 was used as a transmitting
instrument, and that in Fig. 9 as a receiver, so that vocal
communication was only established in one direction....

[Illustration: Fig. 9]

The articulation produced fr