l-station work, so that was the sum
I had in mind to stick to and get--obstinately. Still it had been an
easy job, and only required a few months, and I felt a little shaky and
uncertain. So I asked him to make me an offer. He promptly said he would
give me $100,000. 'All right,' I said. 'It is yours on one condition,
and that is that you do not pay it all at once, but pay me at the rate
of $6000 per year for seventeen years'--the life of the patent. He
seemed only too pleased to do this, and it was closed. My ambition was
about four times too large for my business capacity, and I knew that I
would soon spend this money experimenting if I got it all at once, so
I fixed it that I couldn't. I saved seventeen years of worry by this
stroke."

Thus modestly is told the debut of Edison in the telephone art, to which
with his carbon transmitter he gave the valuable principle of varying
the resistance of the transmitting circuit with changes in the pressure,
as well as the vital practice of using the induction coil as a means of
increasing the effective length of the talking circuit. Without these,
modern telephony would not and could not exist. [6] But Edison, in
telephonic work, as in other directions, was remarkably fertile and
prolific. His first inventions in the art, made in 1875-76, continue
through many later years, including all kinds of carbon instruments
--the water telephone, electrostatic telephone, condenser telephone,
chemical telephone, various magneto telephones, inertia telephone,
mercury telephone, voltaic pile telephone, musical transmitter, and the
electromotograph. All were actually made and tested.

[Footnote 6: Briefly stated, the essential difference
between Bell's telephone and Edison's is this: With the
former the sound vibrations impinge upon a steel diaphragm
arranged adjacent to the pole of a bar electromagnet,
whereby the diaphragm acts as an armature, and by its
vibrations induces very weak electric impulses in the
magnetic coil. These impulses, according to Bell's theory,
correspond in form to the sound-waves, and passing over the
line energize the magnet coil at the receiving end, and by
varying the magnetism cause the receiving diaphragm to be
similarly vibrated to reproduce the sounds. A single
apparatus is therefore used at each end, performing the
double function of transmitter and receiver. With Edison's
telephone a