stretched tight to form a sort of drum, and an armature of magnetized
iron was fastened to its middle. Thus the bit of iron was free to
vibrate, and opposite it was an electro-magnet through which flowed
the current that passed over the line. This acted as the receiver. At
the other end of the wire was a sort of crude harmonica with a clock
spring, reed, and magnet. Bell and Watson had been working upon their
crude apparatus for months, and finally, on June 2d, sounds were
actually transmitted. Bell was afire with enthusiasm; the first great
step had been taken. The electric current had carried sound-vibrations
along the wire and had reproduced them. If this could be done a
telephone which would reproduce whole words and sentences could be
attained.

[Illustration: ALEXANDER GRAHAM BELL]

[Illustration: THOMAS A. WATSON]

So great was Bell's enthusiasm over this achievement that he succeeded
in convincing Sanders and Hubbard that his idea was practical, and
they at last agreed to finance him in his further experiments with the
telephone. A second membrane receiver was constructed, and for many
more weeks the experiments continued. It was found that sounds were
carried from instrument to instrument, but as a telephone they were
still far from perfection. It was not until March of 1876 that Bell,
speaking into the instrument in the workroom, was heard and understood
by Watson at the other instrument in the basement. The telephone had
carried and delivered an intelligible message.

The telephone which Bell had invented, and on which he received a
patent on his twenty-ninth birthday, consisted of two instruments
similar in principle to what we would now call receivers. If you will
experiment with the receiver of a modern telephone you will find
that it will transmit as well as receive sound. The heart of the
transmitter was an electro-magnet in front of which was a drum-like
membrane with a piece of iron cemented to its center opposite the
magnet. A mouthpiece was arranged to throw the sounds of the voice
against the diaphragm, and as the membrane vibrated the bit of iron
upon it--acting as an armature--induced currents corresponding to the
sound-waves, in the coils of the electro-magnet.

Passing over the line the current entered the coils of the tubular
electro-magnet in the receiver. A thin disk of soft iron was fastened
at the end of this. When the current-waves passed through the coils
of the magnet the iron di