producing undulatory currents of electricity for the purpose of multiple
telegraphy. A steel reed, A, was clamped firmly by one extremity to the
uncovered leg _h_ of an electro-magnet E, and the free end of the reed
projected above the covered leg. When the reed A was vibrated in any
mechanical way the battery current was thrown into waves, and electrical
undulations traversed the circuit B E W E', throwing into vibration the
corresponding reed A' at the other end of the circuit. I immediately
proceeded to put my new idea to the test of practical experiment, and
for this purpose I attached the reed A (Fig. 7) loosely by one extremity
to the uncovered pole _h_ of the magnet, and fastened the other
extremity to the centre of a stretched membrane of goldbeaters' skin
_n_. I presumed that upon speaking in the neighbourhood of the membrane
_n_ it would be thrown into vibration and cause the steel reed A to move
in a similar manner, occasioning undulations in the electrical current
that would correspond to the changes in the density of the air during
the production of the sound; and I further thought that the change of
the density of the current at the receiving end would cause the magnet
there to attract the reed 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 from the instrument shown in Fig. 9 was
remarkably distinct, but its great defect consisted in the fact that it
could not be used as a transmitting instrument, and thus two telephones
were required at each station, one for transmitting and one for
receiving spoken messages.
[Illustration: Fig. 10]
It was determined to vary the construction of the telephone shown in
Fig. 8, and I sought, by changing the size and tension of the membrane,
the diameter and thickness of the steel spring, the size and power of
the magnet, and the coils of insulated wire around their poles, to
discover empirically the exact effect of each element of the
combination, and thus to deduce a more perfect form of apparatus. It was
found that a marked increase in the loudness of the sounds resulted from
shortening the length of the coils of wire, and by enlarging the iron
diaphragm which was glued to the membrane. In the latter case, also, the
distinctness of the articulation was improved. Finally, the membrane of
goldbeaters' skin was discarded entirely, and a simple iron plate was
used instead, and at once intelligible articulation was obtained. The
new form of instrument is that shown in Fig. 10, and, as had been long
anticipated, it was proved that the only use of the battery was to
magnetize the iron core, for the effects were equally audible when the
battery was omitted and a rod of magnetized steel substituted for the
iron core of the magnet.
[Illustration: Fig. 11]
It was my original intention, as shown in Fig. 3, and it was always
claimed by me, that the final form of telephone would be operated by
permanent magnets in place of batteries, and numerous experiments had
been carried on by Mr. Watson and myself privately for the purpose of
producing this effect.
At the time the instruments were first exhibited in public the results
obtained with permanent magnets were not nearly so striking as when a
voltaic battery was employed, wherefore we thought it best to exhibit
only the latter form of instrument.
The interest excited by the first published accounts of the operation of
the telephone led many persons to investigate the subject, and I doubt
not that numbers of experimenters have independently discovered that
permanent magnets might be employed instead of voltaic batteries.
Indeed, one gentleman, Professor Dolbear, of Tufts College, not only
claims to have discovered the magneto-electric telephone, but, I
understand, charges me with having obtained the idea from him through
the medium of a mutual friend.
A still more powerful form of apparatus was constructed by using a
powerful compound horseshoe magnet in place of the straight rod which
had been previously used (see Fig. 11). Indeed, the sounds produced by
means of this instrument were of sufficient loudness to be faintly
audible to a large audience, and in this condition the instrument was
exhibited in the Essex Institute, in Salem, Massachusetts, on the 12th
of February, 1877, on which occasion a short speech shouted into a
similar telephone in Boston sixteen miles away, was heard by the
audience in Salem. The tones of the speaker's voice were distinctly
audible to an audience of six hundred people, but the articulation was
only distinct at a distance of about six feet. On the same occasion,
also, a report of the lecture was transmitted by word of mouth from
Salem to Boston, and published in the papers the next morning.
From the form of telephone shown in Fig. 10 to the present form of the
instrument (Fig. 12) is but a step. It is, in fact, the arrangement of
Fig. 10 in a portable form, the magnet F. H. being placed inside the
handle and a more convenient form of mouthpiece provided....
It was always my belief that a certain ratio would be found between the
several parts of a telephone, and that the size of the instrument was
immaterial; but Professor Peirce was the first to demonstrate the
extreme smallness of the magnets which might be employed. And here, in
order to show the parallel lines in which we were working, I may mention
the fact that two or three days after I had constructed a telephone of
the portable form (Fig. 12), containing the magnet inside the handle,
Dr. Channing was kind enough to send me a pair of telephones of a
similar pattern, which had been invented by experimenters at Providence.
The convenient form of the mouthpiece shown in Fig. 12, now adopted by
me, was invented solely by my friend, Professor Peirce. I must also
express my obligations to my friend and associate, Mr. Thomas A. Watson,
of Salem, Massachusetts, who has for two years past given me his
personal assistance in carrying on my researches.
In pursuing my investigations I have ever had one end in view--the
practical improvement of electric telegraphy--but I have come across
many facts which, while having no direct bearing upon the subject of
telegraphy, may yet possess an interest for you.
For instance, I have found that a musical tone proceeds from a piece of
plumbago or retort carbon when an intermittent current of electricity is
passed through it, and I have observed the most curious audible effects
produced by the passage of reversed intermittent currents through the
human body. A breaker was placed in circuit with the primary wires of an
induction coil, and the fine wires were connected with two strips of
brass. One of these strips was held closely against the ear, and a loud
sound proceeded from it whenever the other slip was touched with the
other hand. The strips of brass were next held one in each hand. The
induced currents occasioned a muscular tremor in the fingers. Upon
placing my forefinger to my ear a loud crackling noise was audible,
seemingly proceeding from the finger itself. A friend who was present
placed my finger to his ear, but heard nothing. I requested him to hold
the strips himself. He was then distinctly conscious of a noise (which I
was unable to perceive) proceeding from his finger. In this case a
portion of the induced current passed through the head of the observer
when he placed his ear against his own finger, and it is possible that
the sound was occasioned by a vibration of the surfaces of the ear and
finger in contact.
When two persons receive a shock from a Ruhmkorff's coil by clasping
hands, each taking hold of one wire of the coil with the free hand, a
sound proceeds from the clasped hands. The effect is not produced when
the hands are moist. When either of the two touches the body of the
other a loud sound comes from the parts in contact. When the arm of one
is placed against the arm of the other, the noise produced can be heard
at a distance of several feet. In all these cases a slight shock is
experienced so long as the contact is preserved. The introduction of a
piece of paper between the parts in contact does not materially
interfere with the production of the sounds, but the unpleasant effects
of the shock are avoided.
[Illustration: Fig. 12]
When an intermittent current from a Ruhmkorff's coil is passed through
the arms a musical note can be perceived when the ear is closely applied
to the arm of the person experimented upon. The sound seems to proceed
from the muscles of the fore-arm and from the biceps muscle. Mr. Elisha
Gray has also produced audible effects by the passage of electricity
through the human body.
An extremely loud musical note is occasioned by the spark of a
Ruhmkorff's coil when the primary circuit is made and broken with
sufficient rapidity. When two breakers of different pitch are caused
simultaneously to open and close the primary circuit a double tone
proceeds from the spark.
A curious discovery, which may be of interest to you, has been made by
Professor Blake. He constructed a telephone in which a rod of soft iron,
about six feet in length, was used instead of a permanent magnet. A
friend sang a continuous musical tone into the mouthpiece of a
telephone, like that shown in Fig. 12, which was connected with the soft
iron instrument alluded to above. It was found that the loudness of the
sound produced in this telephone varied with the direction in which the
iron rod was held, and that the maximum effect was produced when the rod
was in the position of the dipping needle. This curious discovery of
Professor Blake has been verified by myself.
When a telephone is placed in circuit with a telegraph line the
telephone is found seemingly to emit sounds on its own account. The most
extraordinary noises are often produced, the causes of which are at
present very obscure. One class of sounds is produced by the inductive
influence of neighbouring wires and by leakage from them, the signals of
the Morse alphabet passing over neighbouring wires being audible in the
telephone, and another class can be traced to earth currents upon the
wire, a curious modification of this sound revealing the presence of
defective joints in the wire.
Professor Blake informs me that he has been able to use the railroad
track for conversational purposes in place of a telegraph wire, and he
further states that when only one telephone was connected with the track
the sounds of Morse operating were distinctly audible in the telephone,
although the nearest telegraph wires were at least fifty feet distant.
Professor Peirce has observed the most singular sounds produced from a
telephone in connection with a telegraph wire during the aurora
borealis, and I have just heard of a curious phenomenon lately observed
by Dr. Channing. In the city of Providence, Rhode Island, there is an
over-house wire about one mile in extent with a telephone at either end.
On one occasion the sound of music and singing was faintly audible in
one of the telephones. It seemed as if some one were practising vocal
music with a pianoforte accompaniment. The natural supposition was that
experiments were being made with the telephone at the other end of the
circuit, but upon inquiry this proved not to have been the case.
Attention having thus been directed to the phenomenon, a watch was kept
upon the instruments, and upon a subsequent occasion the same fact was
observed at both ends of the line by Dr. Channing and his friends. It
was proved that the sounds continued for about two hours, and usually
commenced about the same time. A searching examination of the line
disclosed nothing abnormal in its condition, and I am unable to give you
any explanation of this curious phenomenon. Dr. Channing has, however,
addressed a letter upon the subject to the editor of one of the
Providence papers, giving the names of such songs as were recognized,
and full details of the observations, in the hope that publicity may
lead to the discovery of the performer, and thus afford a solution of
the mystery.
My friend, Mr. Frederick A. Gower, communicated to me a curious
observation made by him regarding the slight earth connection required
to establish a circuit for the telephone, and together we carried on a
series of experiments with rather startling results. We took a couple of
telephones and an insulated wire about 100 yards in length into a
garden, and were enabled to carry on conversation with the greatest ease
when we held in our hands what should have been the earth wire, so that
the connection with the ground was formed at either end through our
bodies, our feet being clothed with cotton socks and leather boots. The
day was fine, and the grass upon which we stood was seemingly perfectly
dry. Upon standing upon a gravel walk the vocal sounds, though much
diminished, were still perfectly intelligible, and the same result
occurred when standing upon a brick wall one foot in height, but no
sound was audible when one of us stood upon a block of freestone.
One experiment which we made is so very interesting that I must speak of
it in detail. Mr. Gower made earth connection at his end of the line by
standing upon a grass plot, whilst at the other end of the line I stood
upon a wooden board. I requested Mr. Gower to sing a continuous musical
note, and to my surprise the sound was very distinctly audible from the
telephone in my hand. Upon examining my feet I discovered that a single
blade of grass was bent over the edge of the board, and that my foot
touched it. The removal of this blade of grass was followed by the
cessation of the sound from the telephone, and I found that the moment I
touched with the toe of my boot a blade of grass or the petal of a daisy
the sound was again audible.
The question will naturally arise, Through what length of wire can the
telephone be used? In reply to this I may say that the maximum amount of
resistance through which the undulatory current will pass, and yet
retain sufficient force to produce an audible sound at the distant end,
has yet to be determined; no difficulty has, however, been experienced
in laboratory experiments in conversing through a resistance of 60,000
ohms, which has been the maximum at my disposal. On one occasion, not
having a rheostat [for producing resistance] at hand, I passed the
current through the bodies of sixteen persons, who stood hand in hand.
The longest length of real telegraph line through which I have attempted
to converse has been about 250 miles. On this occasion no difficulty was
experienced so long as parallel lines were not in operation. Sunday was
chosen as the day on which it was probable other circuits would be at
rest. Conversation was carried on between myself, in New York, and Mr.
Thomas A. Watson, in Boston, until the opening of business upon the
other wires. When this happened the vocal sounds were very much
diminished, but still audible. It seemed, indeed, like talking through a
storm. Conversation, though possible, could be carried on with
difficulty, owing to the distracting nature of the interfering currents.
I am informed by my friend Mr. Preece that conversation has been
successfully carried on through a submarine cable, sixty miles in
length, extending from Dartmouth to the Island of Guernsey, by means of
hand telephones.
PHOTOGRAPHING THE UNSEEN: THE ROENTGEN RAY
H. J. W. DAM
[By permission from _McClure's Magazine_, April, 1896, copyright by
S. S. McClure, Limited.]
In all the history of scientific discovery there has never been,
perhaps, so general, rapid, and dramatic an effect wrought on the
scientific centres of Europe as has followed, in the past four weeks,
upon an announcement made to the Wuerzburg Physico-Medical Society, at
their December [1895] meeting, by Professor William Konrad Roentgen,
professor of physics at the Royal University of Wuerzburg. The first news
which reached London was by telegraph from Vienna to the effect that a
Professor Roentgen, until then the possessor of only a local fame in the
town mentioned, had discovered a new kind of light, which penetrated and
photographed through everything. This news was received with a mild
interest, some amusement, and much incredulity; and a week passed. Then,
by mail and telegraph, came daily clear indications of the stir which
the discovery was making in all the great line of universities between
Vienna and Berlin. Then Roentgen's own report arrived, so cool, so
business-like, and so truly scientific in character, that it left no
doubt either of the truth or of the great importance of the preceding
reports. To-day, four weeks after the announcement, Roentgen's name is
apparently in every scientific publication issued this week in Europe;
and accounts of his experiments, of the experiments of others following
his method, and of theories as to the strange new force which he has
been the first to observe, fill pages of every scientific journal that
comes to hand. And before the necessary time elapses for this article to
attain publication in America, it is in all ways probable that the
laboratories and lecture-rooms of the United States will also be giving
full evidence of this contagious arousal of interest over a discovery so
strange that its importance cannot yet be measured, its utility be even
prophesied, or its ultimate effect upon long established scientific
beliefs be even vaguely foretold.
The Roentgen rays are certain invisible rays resembling, in many
respects, rays of light, which are set free when a high-pressure
electric current is discharged through a vacuum tube. A vacuum tube is a
glass tube from which all the air, down to one-millionth of an
atmosphere, has been exhausted after the insertion of a platinum wire in
either end of the tube for connection with the two poles of a battery or
induction coil. When the discharge is sent through the tube, there
proceeds from the anode--that is, the wire which is connected with the
positive pole of the battery--certain bands of light, varying in colour
with the colour of the glass. But these are insignificant in comparison
with the brilliant glow which shoots from the cathode, or negative wire.
This glow excites brilliant phosphorescence in glass and many
substances, and these "cathode rays," as they are called, were observed
and studied by Hertz; and more deeply by his assistant, Professor
Lenard, Lenard having, in 1894, reported that the cathode rays would
penetrate thin films of aluminum, wood, and other substances, and
produce photographic results beyond. It was left, however, for Professor
Roentgen to discover that during the discharge quite other rays are set
free, which differ greatly from those described by Lenard as cathode
rays. The most marked difference between the two is the fact that
Roentgen rays are not deflected by a magnet, indicating a very essential
difference, while their range and penetrative power are incomparably
greater. In fact, all those qualities which have lent a sensational
character to the discovery of Roentgen's rays were mainly absent from
those of Lenard, to the end that, although Roentgen has not been working
in an entirely new field, he has by common accord been freely granted
all the honors of a great discovery.
Exactly what kind of a force Professor Roentgen has discovered he does
not know. As will be seen below, he declines to call it a new kind of
light, or a new form of electricity. He has given it the name of the X
rays. Others speak of it as the Roentgen rays. Thus far its results only,
and not its essence, are known. In the terminology of science it is
generally called "a new mode of motion," or, in other words, a new
force. As to whether it is or not actually a force new to science, or
one of the known forces masquerading under strange conditions, weighty
authorities are already arguing. More than one eminent scientist has
already affected to see in it a key to the great mystery of the law of
gravity. All who have expressed themselves in print have admitted, with
more or less frankness, that, in view of Roentgen's discovery, science
must forthwith revise, possibly to a revolutionary degree, the long
accepted theories concerning the phenomena of light and sound. That the
X rays, in their mode of action, combine a strange resemblance to both
sound and light vibrations, and are destined to materially affect, if
they do not greatly alter, our views of both phenomena, is already
certain; and beyond this is the opening into a new and unknown field of
physical knowledge, concerning which speculation is already eager, and
experimental investigation already in hand, in London, Paris, Berlin,
and, perhaps, to a greater or less extent, in every well-equipped
physical laboratory in Europe.