Speaker 1: Section thirty of the Science History of the Universe, Volume three.
Speaker 1: This is a LibriVox recording. All LibriVox recordings are in
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Speaker 1: Volume three, edited by Francis Rolt Wheeler Electricity, Chapter ten
Speaker 1: the Electromagnetic Telegraph, Part two. As the popularity of the
Speaker 1: telegraph increased and the number of line wires grew large,
Speaker 1: attempts were made to make one line wire transmit more
Speaker 1: than one message at the same time. Various schemes have
Speaker 1: been tried, most of which have failed by reason of
Speaker 1: the complications of the apparatus and the subsequent troubles attending them.
Speaker 1: The step in the direction of utilizing the line wire
Speaker 1: more fully was the invention of the duplex system by
Speaker 1: doctor Wilhelm Genthel in eighteen fifty three. This system was
Speaker 1: improved by Carl Friskin of Hanover until it lacked only
Speaker 1: one essential element, means to overcome the condenser like action
Speaker 1: of the long line wire. It was not until eighteen
Speaker 1: seventy two that this was supplied by Joseph B. Stearns
Speaker 1: of Boston, who introduced a condenser into the artificial line
Speaker 1: of the duplex system, and by adjusting it made the
Speaker 1: artificial line behave like the line wire itself. This important
Speaker 1: edition made the system entirely successful, so that it became
Speaker 1: possible to transmit two messages in opposite directions at the
Speaker 1: same time. Following the success of the duplex system, there
Speaker 1: was developed a method by which two messages could be
Speaker 1: sent simultaneously in the same direction, and it was but
Speaker 1: a step to combine these two systems so that two
Speaker 1: messages could be sent each way simultaneously. This last is
Speaker 1: known as the quadruplex system and was immediately successful because
Speaker 1: there were no delicate adjustments to be made and no
Speaker 1: rotating parts as in some of the synchronous telegraphs which
Speaker 1: have been tried from time to time. As early as
Speaker 1: eighteen fifty two, Moses G. Farmer of Salem, Massachusetts devised
Speaker 1: a synchronous multiple telegraph in which he proposed to employ
Speaker 1: two rotating switches, one at each end of the line,
Speaker 1: to successively and simultaneously join the several operators at one
Speaker 1: station with those of another. The idea was to connect
Speaker 1: two operators for an instant pass on to the next
Speaker 1: two and so on, returning to the first two operators
Speaker 1: so quickly that the relay of the receiving operator would
Speaker 1: not have had time to change, nor the key of
Speaker 1: the sender to make a dot. The impulses of the
Speaker 1: current had therefore to be made with great frequency, and
Speaker 1: the control of this impulsive current was the principal cause
Speaker 1: of failure. Another difficulty was the main time of the
Speaker 1: rotating switches in synchronism. The public is occasionally startled with
Speaker 1: an announcement that someone has invented a telegraph by which
Speaker 1: a wire may be utilized for twenty or perhaps forty transmissions,
Speaker 1: but usually it is the old wanderer in a new Garb.
Speaker 1: Speed by this method, however, is limited far Within the
Speaker 1: bounds of these statements, it might seem that it would
Speaker 1: be only necessary to multiply the number of contacts and
Speaker 1: to increase the velocity of the rotating arms, but the
Speaker 1: limit in this direction is soon reached, for only a
Speaker 1: certain number of impulses can be transmitted over a line
Speaker 1: within a certain period with force sufficient to produce signals.
Speaker 1: Many valuable improvements have been made in recent years in
Speaker 1: this class of telegraphy, but large as the art has grown.
Speaker 1: The great object of all has been to obtain more
Speaker 1: perfect synchronism, that is to say, to cause two mechanically
Speaker 1: independent arms to rotate at the same speed. One of
Speaker 1: the most recent of these synchronous telegraphs, and which is
Speaker 1: now being exploited, is that invented by mister Delaney. The
Speaker 1: principle is that of Farmer, but the method used to
Speaker 1: hold the rotating switches in synchronism is extremely ingenious. It
Speaker 1: is stated that one thousand words permitted may be transmitted
Speaker 1: over a single wire. The messages are prepared on a
Speaker 1: tape by a punching machine and received on a chemically
Speaker 1: prepared strip of paper. The idea of printing the dispatch
Speaker 1: is not new. In the early days of the electric telegraph,
Speaker 1: eighteen forty one, Wheatstone took out a patent for printing
Speaker 1: the message in ordinary letters upon a strip of paper.
Speaker 1: Since then, many inventors have followed out the same idea
Speaker 1: with more or less success. The most perfect of all
Speaker 1: these systems, however, is that invented by Professor David E. Hughes,
Speaker 1: which in a modified form is now very generally used
Speaker 1: as a news or stock ticker. Figure forty five shows
Speaker 1: the connections. For s such a telegraph, the sending station
Speaker 1: is at A and one of the receiving stations is
Speaker 1: at B. The line is fed with an alternating current
Speaker 1: produced by reversing commutator four. This alternating current does not
Speaker 1: affect printing relay five, but does operate polar relay six,
Speaker 1: which in turn operates the escapement. Reverser four is driven
Speaker 1: by constant speed motor one and has as many segments
Speaker 1: as there are characters on the type wheel. The escape
Speaker 1: wheel ten is provided with an equal number of teeth,
Speaker 1: so that each revolution of reverser four will produce one
Speaker 1: revolution of type wheel seven. On the shaft with the
Speaker 1: reverser is rigidly mounted a cylinder provided with a number
Speaker 1: of pins arranged spirally as shown. Each pin is in
Speaker 1: line with a segment of the reverser and also in
Speaker 1: line with a pin fastened to the keyboard. Depressing a
Speaker 1: given key will always stop the cylinder and therefore type
Speaker 1: wheel seven in the same place. The connection to the
Speaker 1: motor one is made with friction clutch two, which slips
Speaker 1: when cylinder three is stopped. Now it is evident if
Speaker 1: type wheel seven is started with its characters in certain
Speaker 1: position and is rotated by a motor through gear eleven
Speaker 1: and controlled by escapement magnet six, that it will always
Speaker 1: remain in the same relative position with cylinder three, and
Speaker 1: that the operator can stop the type wheel in any
Speaker 1: desired position. If the type wheel stops because of the
Speaker 1: arrest of the cylinder three by depression of a key,
Speaker 1: the current ceases to alternate, and magnet five has time
Speaker 1: to draw up its armature eight and press the tape
Speaker 1: against the type wheel, thus printing the character which corresponds
Speaker 1: to key depressed at the sending station. These are ingenious
Speaker 1: arrangements for reproducing at a distant point handwriting drawings, et cetera.
Speaker 1: One of the first of these is known as Casselli's
Speaker 1: pen telegraph, because as the reproduction may be of the
Speaker 1: same size or even larger than the original. The message
Speaker 1: to be sent is written with an insulating ink on
Speaker 1: a piece of tinfoil and received on a sheet of
Speaker 1: chemically prepared paper upon which a blue dot is left
Speaker 1: at each current impulse. The motions of the marking style
Speaker 1: at the two stations are controlled by similar pendulums. In
Speaker 1: the Denisen system, these pendulums are forced to vibrate together
Speaker 1: through the control of electro magnets operated by the same
Speaker 1: alternating current. The most recent and useful of these arrangements
Speaker 1: is the telautograph. The message is reproduced as fast as
Speaker 1: it is written. Drawings or sketches are transmitted with great accuracy.
Speaker 1: In fact, every motion of the sending pen is instantly
Speaker 1: followed by the receiver. Some of these are in use
Speaker 1: in the United States Army. The insulation of conductors for
Speaker 1: use under water was made possible by the discovery of
Speaker 1: Guda percha by an ink English surgeon in India in
Speaker 1: eighteen forty two. It is extremely probable that the widespread
Speaker 1: use of submarine cables would have been postponed many years
Speaker 1: had this substance remain unknown. One of the first cables
Speaker 1: insulated by this material, and possibly the very first, was
Speaker 1: laid in eighteen forty eight across the Hudson River from
Speaker 1: Jersey City to New York. In eighteen fifty a cable
Speaker 1: was laid across the channel from Dover to Calais, but
Speaker 1: it was unprotected by any sheathing or armour, and it
Speaker 1: lasted but a single day. In the following year, the
Speaker 1: experiment was repeated, this time with a cable protected by
Speaker 1: a number of heavy iron wires. The operation was successful,
Speaker 1: and permanent telegraph communication was established. During the next few years,
Speaker 1: the number of submarine cables increased rapidly, as did also
Speaker 1: their length, although on account of ignorance in regard to
Speaker 1: many conditions necessary to ensure the best success, failures were numerous.
Speaker 1: Many people began to consider the feasibility of a line
Speaker 1: connecting the continents across the Atlantic Ocean. A few sanguine
Speaker 1: capitalists combined to further the enterprise, and through the undaunted
Speaker 1: courage and faith of an American mister Cyrus W. Field,
Speaker 1: the purely financial obstacles were surmounted. Unfortunately, the electrical and
Speaker 1: engineering problems to be met with were not understood, and
Speaker 1: the first cable of eighteen fifty eight, after gasping for
Speaker 1: breath for a few short weeks, lay dumb forever at
Speaker 1: the bottom of the sea. Something of the character of
Speaker 1: this cable may be learned from the following brief description
Speaker 1: by Sir William Thompson, to whom, more than to any
Speaker 1: other one man the world is indebted for the success
Speaker 1: of submarine telegraphy in the year eighteen fifty seven. As
Speaker 1: much iron as would make a cube twenty feet wide
Speaker 1: was drawn into wire long enough to extend from the
Speaker 1: Earth to the moon and bind several times around each globe.
Speaker 1: This wire was made into one hundred and twenty six
Speaker 1: lengths of two thousand, five hundred miles and spun into
Speaker 1: eighteen strands of seven wires each A single strand of
Speaker 1: seven copper wires of the same length, weighing in all
Speaker 1: one hundred and ten grains per foot, was three times
Speaker 1: coated with Gudha percha to an entire outer thickness of
Speaker 1: zero point four of an inch, and this was served
Speaker 1: outside with two hundred and forty tons of tarred yarn,
Speaker 1: and then laid over with the eighteen strands of iron
Speaker 1: wire in long continuous spirals, and passed through a bath
Speaker 1: of melted pitch. An attempt to lay this cable in
Speaker 1: eighteen fifty seven resulted in the loss of four hundred
Speaker 1: or five hundred miles by breaking from the stern of
Speaker 1: the ship from which it was run. After some further experimentation,
Speaker 1: it was determined to employ two ships to lay it
Speaker 1: in the following year, and accordingly, on the twenty ninth
Speaker 1: of July eighteen fifty eight, the Niagara and the Agamemnon,
Speaker 1: each loaded with half the cable, met in mid ocean,
Speaker 1: joined the ends and started the Niagara for the west
Speaker 1: and the Agamemnon for the east. On the fifth of August,
Speaker 1: the ends were successfully landed on the opposite shores of
Speaker 1: the Atlantic. The cable was known to be in bad
Speaker 1: condition before the laying was completed, and the earnest but
Speaker 1: ill advised efforts which were made to force it to
Speaker 1: work during its brief period of activity only tended to
Speaker 1: shorten its life. Communication of a very irregular and unsatisfactory
Speaker 1: character was maintained for several weeks. The admirable mirror galvanometer,
Speaker 1: which had just been devised by Sir William Thompson, was
Speaker 1: for the first time in use at the Valencia end,
Speaker 1: while for a time the attempt was made to use
Speaker 1: the ordinary receiving apparatus which had been provided by the
Speaker 1: company at Newfoundland. Later the galvanometer was put in use
Speaker 1: on this side, but not before very powerful currents had
Speaker 1: been used on the cable. In fact, Sir William Thompson
Speaker 1: has declared his belief that if proper methods of handling
Speaker 1: the cable electrically had been in use, from the beginning,
Speaker 1: its performance would have been lasting and in the main satisfactory.
Speaker 1: Owing to the fragmentary character of many of the messages transmitted,
Speaker 1: a single sentence from that of the Queen to the
Speaker 1: President having been received on August sixteenth, and the remainder
Speaker 1: twenty four hours later. Many persons in both Europe and
Speaker 1: America became skeptical as to the transmission of signals, and
Speaker 1: not a few even doubted that the cable had been laid.
Speaker 1: As a matter of fact, four hundred messages containing over
Speaker 1: four thousand words were sent. On September. First interchange of
Speaker 1: messages ceased, but on October twentieth the cable spoke its
Speaker 1: last words, two hundred for which were read at Valencia,
Speaker 1: being part of a message giving the number of battery
Speaker 1: cells then on the line. From that date, the splendid
Speaker 1: combination of matter lay at the bottom of the sea,
Speaker 1: forever useless. But it had not lived in vain. The
Speaker 1: possibility of the thing was demonstrated, and it only remained
Speaker 1: to surmount the obstacles which this trial had shown. During
Speaker 1: a few years succeeding this first attempt, the problem was
Speaker 1: studied in the light of the experience which it had afforded.
Speaker 1: Another trial was made in eighteen sixty five, this time
Speaker 1: by the Great Eastern, a vessel, which offered many advantages
Speaker 1: for cable laying. After about two thirds of the distance
Speaker 1: was run, the cable broke and further operations were postponed
Speaker 1: until the following year, when a complete cable was successfully laid,
Speaker 1: and that of eighteen sixty five picked up, spliced and finished.
Speaker 1: Since then other lines had been placed across the Atlantic,
Speaker 1: and now the operations of laying an ocean cable attracts
Speaker 1: no attention. One of the difficulties encountered in attempting to
Speaker 1: send messages through such a long cable was that, due
Speaker 1: to the electrostatic capacity of the cable, the cable acts
Speaker 1: like a very large condenser, so that when the voltage
Speaker 1: is applied at one end, the current does not instantly
Speaker 1: rise to its steady value, but takes several seconds, and
Speaker 1: when the supply of voltage is disconnected, the current continues
Speaker 1: to flow in order to signal rapidly. Therefore, it was
Speaker 1: necessary to overcome this action and to use very delicate
Speaker 1: receiving instruments for this purpose. Sir William Thompson, Lord Kelvin
Speaker 1: devised the well known siphon recorder, which is really a
Speaker 1: sensitive galvanometer whose moving coil carries a siphon tube filled
Speaker 1: with ink, the ink being ejected from it in fine
Speaker 1: drops on a strip of paper. To produce these fine drops,
Speaker 1: the siphon tube is connected to a small electrostatic machine
Speaker 1: so that the tube is allow Although the telephone has
Speaker 1: made such rapid advances as a means of communication, the
Speaker 1: telegraph still holds its own field. The greater simplicity of
Speaker 1: the latter, the less expensive lines, the greater distances to
Speaker 1: which messages can be transmitted, all combined for its preservation.
Speaker 1: The flattening out of the waves on a telephone line
Speaker 1: due to the condenser like action of the line has
Speaker 1: not yet been overcome. The difference between the telephonic waves
Speaker 1: at the beginning and end of a line may be
Speaker 1: compared to that between the noisy exhaust of an automobile
Speaker 1: motor without and with a muffler. In the case of
Speaker 1: the transmission of telephone waves, it is therefore a problem
Speaker 1: of how to rid the line of its muffler. End
Speaker 1: of Section thirty