TELEPHONY.
In the foregoing chapters I have described the method of transmitting
musical tones telegraphically and its applications to multiple
telegraphy, as well as to a mode of communicating with a moving
railroad-train. As I stated in a former chapter, after discovering a
method of transmitting harmony as well as melody, I had in mind two
lines of development, one in the direction of multiple telegraphy, and
the other that of the transmission of articulate speech. I will not
attempt to give the names of all the people who have contributed to the
development of the telephone (as this alone would fill a volume) but
only describe my own share in the work--leaving history to give each one
due credit for his part. While I do not intend, here, to enter into any
controversy regarding the priority of the invention of the telephone, I
wish to say that from the time I began my researches, in the winter of
1873-4, until some time after I had filed my specification for a
speaking or articulating telephone, in the winter of 1875-76, I had no
idea that any one else had done or was doing anything in this direction.
I wish to say further that if I had filed my description of a telephone
as an application for a patent instead of as a caveat, and had
prosecuted it to a patent, without changing a word in the specification
as it stands to-day, I should have been awarded the priority of
invention by the courts. I am borne out in this assertion by the highest
legal authority. In law, a _caveat_ (Latin word, meaning "Let him
beware") is a warning to other inventors, to protect an incomplete
invention; whereas in fact the invention to be protected may be
complete. An _application_ for a patent is presumed by the law to be for
a completed invention; but it may be, and very often is, incomplete. It
would often make a very great difference if decisions were rendered
according to the facts in the case rather than according to rules of law
and practice, that sometimes work great injustice to individuals.
As has been said in another chapter, in the summer of 1874 I went to
Europe in the interest of the telephone, taking my apparatus, as then
developed, with me. I came home early in the fall and resumed my
experimental work. Many interesting as well as amusing things occurred
during these experiments.
I remember that in the fall or early winter of 1874 I was in Milwaukee
with my apparatus carrying on some experiments on a wire between
Milwaukee and Chicago. I had my musical transmitter along, and one
evening, for the entertainment of some friends at the Newhall House, a
wire was stretched across the street from the telegraph office into one
of the rooms of the hotel. A great number of tunes were played at the
telegraph-office by Mr. Goodridge, who was my assistant at that time,
which were transmitted across the street, as before stated. In those
days it was a common practice in telegraphy to use one battery for a
great number of lines. For instance, starting with one ground-wire which
connected with, say, the negative pole of the battery, from the positive
pole two, three or a half-dozen lines might be connected, running in
various directions, connecting with the ground at the further end, thus
completing their circuits. For use in transmitting tones across the
street that evening we connected our line-wire on to the telegraph
company's battery, which consisted of 100 or more cells, and which had
four or five more lines radiating from the end of the battery to
different parts of Wisconsin. Our line was tapped on to the battery
(without changing any of its connections) twenty cells from the
ground-wire. In transmitting, each vibration would momentarily shut off
these twenty cells from the lines that were connected with the whole
battery. The effect of this (an effect that we did not anticipate at the
time) was to send a vibratory current out on all the lines that were
connected with that single battery as well as across the street. A great
many familiar tunes were played during the course of an hour or two
which, unconsciously for us, were creating great consternation
throughout the State of Wisconsin, in many of the offices through which
these various lines passed.
Next morning reports and inquiries began to come in from various towns
and cities west, northwest and north, giving details of the phenomena
that were noticed on the instruments located in the various offices
along the lines. They reported their relays as singing tunes; one party
said he thought the instruments were holding a prayer-meeting from the
fact that they seemed to be singing hymn-tunes for quite a while, but
this notion was finally dissipated, because they grew hilarious and sang
"Yankee Doodle."
One operator, up in the pine woods of northern Wisconsin, did not seem
to take the cheerful view of it that some of the others did. He was
sitting alone in the telegraph-office that evening when he thought he
heard the notes of a bugle in the distance; he got up and went to the
door to listen, but could hear nothing; but on coming back into the room
he heard the same bugle notes very faintly. He was inclined to be
somewhat superstitious and grew very nervous; finally, on looking
around, he located the sound in his relay, but this did not help matters
with him. With superstitious awe he listened to the instrument for a few
moments, while it gave out the solemn tones of "Old Hundred," then it
suddenly jumped into a hilarious rendering of "Yankee Doodle." This was
too much for our nervous friend, and hastily putting on his overcoat, he
left the office for the night.
On another occasion, when I was giving a lecture in one of the cities
outside of Chicago, where exhibitions of music transmitted from Chicago
were given, one of the operators along the line was very much astonished
by his switchboard suddenly becoming musical. Orders had been given for
the instruments in all the local offices to be cut out of the particular
line that I was using. Hence the instrument in this particular office
was not in the circuit through which the tunes were being transmitted.
The wire, however, ran through his switchboard, and owing probably to a
loose connection, or an induced effect, there was a spark that leaped
across a short space at each electrical pulsation that passed through
the line, thus reproducing the notes of the various tunes played.
You will remember in one of the chapters on sound (Volume II.), it is
stated that a musical tone is made up of a succession of sounds
repeated at equal intervals, and that the pitch of the tone is
determined by the number of sound-impulses per second. Applying this law
to the sparks, you will be able to see how the switchboard played tunes
for the operator.
In the foregoing experiments in transmitting musical tones
telegraphically, I used a great many different varieties of receivers.
Some of them were designed with metal diaphragms mounted over single
electromagnets, not unlike the receiver of an ordinary telephone. These
instruments would both transmit and receive articulate speech when
placed in circuit with the right amount of battery to furnish the
necessary magnetism. However, they were not used in that way at the time
they were first made--in 1874. These I called common receivers, as they
were designed to reproduce all tones equally well. I designed and
constructed another form of receiver, based somewhat upon the theory of
the harmonic telegraph.
This consisted of an electromagnet of considerable size, mounted upon a
wooden rod about ten feet long. Mounted upon this rod were also
resonating boxes or tubes made of wood of the right size to have their
air-cavities correspond with the various pitches of the
transmitting-reeds, so that each tone would be re-enforced by some one
of these air-cavities, thus giving a louder and more resonant effect to
the musical notes.
Here were two types of receiver, one that would receive one sound as
well as another, but none of them so loud, while the other was
constructed on the principle of selection and re-enforcement, so that a
particular note would be sounded by the box having a cavity
corresponding to the pitch of the tone, and was much louder and of much
better quality than I could get from the diaphragm receiver. One of
these receivers pointed to the harmonic telegraph and the other to the
speaking telephone. I knew that I had a receiver that would reproduce
articulate speech or anything else that could be transmitted.
My first conceptions of an articulate speech-transmitter were somewhat
complicated. I conceived of a funnel made of thin metal having a great
number of little riders, insulated from the funnel at one end and
resting lightly in contact with the funnel at the other end. These
riders were to be made of all sizes and weights so as to be responsive
to all rates of vibration. In the light of the present day we know that
such an arrangement would have transmitted articulate speech, but
perhaps not so well as a single point would do when properly adjusted.
My mind clung to this idea till in the fall of 1875, when an observation
I made upon the street changed the whole course of my thinking and
solved the problem. The incident I refer to took place in Milwaukee,
where I was then experimenting. One day while out on an errand I noticed
two boys with fruit-cans in their hands having a thread attached to the
center of the bottom of each can and stretched across the street,
perhaps 100 feet apart. They were talking to each other, the one holding
his mouth to his can and the other his ear. At that time I had not heard
of this "lovers' telegraph," although it was old. It is said to have
been used in China 2000 years ago.
The two boys seemed to be conversing in a low tone with each other and
my interest was immediately aroused. I took the can out of one of the
boy's hands (rather rudely as I remember it now), and putting my ear to
the mouth of it I could hear the voice of the boy across the street. I
conversed with him a moment, then noticed how the cord was connected at
the bottom of the two cans, when, suddenly, the problem of electrical
speech-transmission was solved in my mind. I did not have an opportunity
immediately to construct an instrument, as I had a partner who was
furnishing money for the development of the harmonic telegraph and would
not listen to any collateral experiments. I remember sitting down by
this partner one day and telling him what I could do in the way of
transmitting speech through a wire. I told him I thought it would be
very valuable if worked out. He gave me a look that I shall never
forget, but he did not say a word. The look conveyed more meaning than
all the words he could have said, and I did not dare broach the subject
again.
However, as soon as I found opportunity, without saying a word to
anybody except my patent lawyer, I filed a description, accompanied by
drawings, of a speaking telephone which stands in history to-day as the
first complete description on record of the operation of the speaking
telephone. It described an apparatus which, when constructed, worked as
described, and it is a matter of history that the first articulate
speech electrically transmitted in this country was by a transmitter
constructed on the principle described, and almost identically after the
drawings in my caveat. While the transmitter described in this caveat
was not the best form, it would transmit speech, and it contained the
foundation principle of all the telephone transmitters in use to-day.
There are two methods of transmitting speech. One is known as the
magneto method and the other that of varying the resistance of the
circuit. My first transmitter was devised on the latter principle.
I append to this extracts from my specification filed Feb. 14, 1876:
_To All Whom It May Concern:_--Be it known that I, Elisha Gray
of Chicago, in the County of Cook and State of Illinois, have
invented a new art of transmitting vocal sounds
telegraphically, of which the following is a specification: It
is the object of my invention to transmit the tones of the
human voice through a telegraphic circuit, and reproduce them
at the receiving-end of the line, so that actual conversations
can be carried on by persons at long distances apart. I have
invented and patented methods of transmitting musical
impressions or sounds telegraphically, and my present invention
is based upon a modification of the principle of said
invention, which is set forth and described in letters patent
of the United States, granted to me July 27, 1875, respectively
numbered 166,095 and 166,096, and also in an application for
letters patent of the United States, filed by me, Feb. 23,
1875. * * * My present belief is that the most effective method
of providing an apparatus capable of responding to the various
tones of the human voice is a tympanum, drum, or diaphragm,
stretched across one end of the chamber, carrying an apparatus
for producing fluctuations in the potential of the electric
circuit and consequently varying in its power. * * * The
vibrations thus imparted are transmitted through an electric
circuit to the receiving-station, in which circuit is included
an electromagnet of ordinary construction, acting upon a
diaphragm to which is attached a piece of soft iron, and which
diaphragm is stretched across a receiving vocalizing chamber
_C_, somewhat similar to the corresponding vocalizing chamber
_A_.
The diaphragm at the receiving-end of the line is thus thrown
into vibrations corresponding with those at the
transmitting-end, and audible sounds or words are produced.
The obvious practical application of my improvement will be to
enable persons at a distance to converse with each other
through a telegraphic circuit, just as they now do in each
other's presence, or through a speaking-tube.
I claim as my invention the art of transmitting vocal sounds or
conversations telegraphically through an electric circuit.
This specification was accompanied by cuts of the transmitter and
receiver connected by a line-wire and showing one person talking to the
transmitter and another listening at the receiver. These cuts may be
seen in various books on the subject of telephony.