in the field of telephony, Bell labored faithfully for regular periods with the devices in which his patrons were interested.  The remainder of his time and energy he put upon the telephone.  The basis of his telephone was still the disk or diaphragm which would vibrate when the sound-waves of the voice were thrown against it.  Behind this were mounted various kinds of electro-magnets in series with the electrified wire over which the inventor hoped to send his messages.  For three years they labored with this apparatus, trying every conceivable sort of disk.  It is easy to pass over those three years, filled as they were with unceasing toil and patient effort, because they were drab years when little of interest occurred.  But these were the years when Bell and Watson were “going to school,” learning how to apply electricity to this new use, striving to make their apparatus talk.  How dreary and trying these years must have been for the experimenters we may well imagine.  It requires no slight force of will to hold oneself to such a task in the face of failure after failure.

By June of 1875 Bell had completed a new Instrument.  In this the diaphragm was a piece of gold-beater’s skin, which Bell had selected as most closely resembling the drum in the human ear.  This was 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.