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<v Speaker 1>Section thirty two of the Science History of the Universe,

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<v Speaker 1>Volume three. This is a LibriVox recording. All LibriVox recordings

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<v Speaker 1>are in the public domain. For more information or to volunteer,

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<v Speaker 1>please visit LibriVox dot org. Recording by Amelia Chesley, The

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<v Speaker 1>Science History of the Universe, Volume three, edited by Francis

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<v Speaker 1>Rolt Wheeler. Electricity, Chapter eleven, Part two. It was at

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<v Speaker 1>once first seen by many experimenters, among them Sir Oliver Lodge,

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<v Speaker 1>that with the old forms of apparatus there would be

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<v Speaker 1>interference between wireless stations, as the receivers would respond to

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<v Speaker 1>all wavelengths. To understand how it is possible to make

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<v Speaker 1>as sending or a receiving circuit which will send out

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<v Speaker 1>or respond to only one kind of electric wave, let

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<v Speaker 1>the pendulum analogy again be used. In order to set

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<v Speaker 1>a pendulum in motion, it is necessary that the impulsive

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<v Speaker 1>force should be imparted to it the same number of

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<v Speaker 1>times per second in which the pendulum naturally oscillates. Even

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<v Speaker 1>if stray forces are applied but are not properly timed,

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<v Speaker 1>the effect on the pendulum will be small, whereas a

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<v Speaker 1>very minute but properly timed force acting for some time

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<v Speaker 1>will produce considerable motion in a large pendulum. All these

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<v Speaker 1>characteristics of the pendulum may be applied to the electric circuit,

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<v Speaker 1>the natural period of vibration, the small effect of a

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<v Speaker 1>lot of waves differing in length, and the large effect

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<v Speaker 1>of a succession of feeble but similar waves. Sir Oliver

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<v Speaker 1>Lodge in eighteen ninety seven took out a patent for

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<v Speaker 1>a syntonic system of wireless telegraphy based directly on his

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<v Speaker 1>own work on the discharge of latent jars and on

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<v Speaker 1>Hertz's experimental results. The transmitter consisted of two large cones

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<v Speaker 1>of sheet metal, placed with their axis in a vertical

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<v Speaker 1>line and having a spark gap between their apecies. In

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<v Speaker 1>another form of transmitter, a single stole metal sphere separated

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<v Speaker 1>by small spark gaps from the terminals of an induction

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<v Speaker 1>coil was used as a radiator. Both types produced direct

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<v Speaker 1>Hertzian radiation, the latter giving waves of very high frequency.

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<v Speaker 1>The spherical oscillator was partially enclosed by a copper cylinder

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<v Speaker 1>open at one end in order that the rays might

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<v Speaker 1>be condensed in one direction. The receiver for use in

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<v Speaker 1>connection with the large cones consisted of two smaller cones

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<v Speaker 1>connected through the primary of a small transformer, the secondary

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<v Speaker 1>of which was connected to the coherer circuit. The dimensions

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<v Speaker 1>of the transmitter and receiver were adjusted to give ecifrequent

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<v Speaker 1>natural vibrations and therefore resonance. No earth connection was made,

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<v Speaker 1>as it was desired that the transmission should be purely

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<v Speaker 1>by means of free radiations. The early conical form of

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<v Speaker 1>radiator has now given place to the horizontal conductors. Stations

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<v Speaker 1>in which this latter arrangement has been adopted are now

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<v Speaker 1>working in various parts of the world. As soon as

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<v Speaker 1>Marconi had modified his system of telegraphy, he applied it

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<v Speaker 1>immediately to the conquest of record distances in radio telegraphic transmission.

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<v Speaker 1>To this end, he set up a station at the

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<v Speaker 1>Lizard Cornwall, which was immediately put into communication with Marconi's

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<v Speaker 1>experimental station at Saint Catharine's Isle of Wight, at a

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<v Speaker 1>distance of three hundred kilometers about two hundred miles, in

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<v Speaker 1>which he used an aerial conductor consisting of four vertical

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<v Speaker 1>wires standing about five feet from one another about one

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<v Speaker 1>hundred and forty four feet in height, along with a

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<v Speaker 1>strip of wire netting of the same length under the

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<v Speaker 1>new system, the energy required to telegraph to a given

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<v Speaker 1>distance was very much diminished, so that one hundred and

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<v Speaker 1>fifty watts sufficed to communicate to the three hundred kilometer distance.

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<v Speaker 1>Encouraged by the results of the experiments in communication between

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<v Speaker 1>Saint Catharines and the Lizard, Marconi put his whole heart

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<v Speaker 1>into the attempt to resolve the artous problem of establishing

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<v Speaker 1>transatlantic radio telegraphic communication. Repeated experiments had shown that long waves,

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<v Speaker 1>either by successive reflection or diffraction, could turn round the

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<v Speaker 1>surface of the Earth, so that their transmission to very

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<v Speaker 1>great distances resolved itself only into a question of sufficient

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<v Speaker 1>power in the transmitting apparatus and sufficient sensibility in the

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<v Speaker 1>receiving But these necessitated large financial means, which would, however,

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<v Speaker 1>not be wanting in a man whose business acumen was

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<v Speaker 1>not less surprising than his experimental ability. Being largely subsidized

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<v Speaker 1>by the Marconi Wireless Telegraph Company, Marconi began early in

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<v Speaker 1>nineteen oh one, unknown to everyone, his trials, by establishing

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<v Speaker 1>two specially powerful stations, at Poldew near Cape Blizzard and

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<v Speaker 1>Cornwall on one side of the ocean, and at Cape

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<v Speaker 1>cod in Massachusetts on the other side. The results of

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<v Speaker 1>these first trials are not known, and, judging by the

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<v Speaker 1>sou islands maintained in this regard, they were probably negative.

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<v Speaker 1>The two stations, that had cost the sum of more

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<v Speaker 1>than fifteen thousand pounds were destroyed by storms. In September

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<v Speaker 1>of the same year. Marconi caused the station at Pouldu

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<v Speaker 1>to be rebuilt, furnishing it with powerful machines and radiators,

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<v Speaker 1>and decided to attempt communication with Saint John's Newfoundland, that

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<v Speaker 1>is to say, to a lesser distance than that previously

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<v Speaker 1>chosen of about fifteen hundred miles at Saint John's Newfoundland,

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<v Speaker 1>where Marconi had obtained from the government every facility for

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<v Speaker 1>making the trials. The installation was of the simplest character,

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<v Speaker 1>consisting of a receiving station only. The area line was

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<v Speaker 1>maintained at a height of about four hundred feet by

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<v Speaker 1>means of a kite. Marconi had already agreed with the

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<v Speaker 1>station at Pauldo that every day, at six o'clock in

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<v Speaker 1>the evening, a long series of letter s should be sent.

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<v Speaker 1>This letter, in the Morse alphabet, consists of three dots.

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<v Speaker 1>The message was received telephonically on the twelfth of December

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<v Speaker 1>nineteen oh one, Marconi announced that he had received the

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<v Speaker 1>different ESS's at equal and determinate intervals, and he proclaimed

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<v Speaker 1>that it was practically, physically and mathematically impossible that the

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<v Speaker 1>signals could have come from any other place but Cape Lizard.

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<v Speaker 1>In the summer of nineteen oh two, mister Marconi made

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<v Speaker 1>an interesting comparative test of his first coherer system and

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<v Speaker 1>his second magnetic detector system. The ship Carlo Alberta was

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<v Speaker 1>fitted out with both sets of receiving apparatus. By previous arrangement,

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<v Speaker 1>a set of signals from the Poldu station was to

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<v Speaker 1>be sent out at certain hours of the day. As

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<v Speaker 1>the voyage towards Kronstadt proceeded, the signals diminished in strength,

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<v Speaker 1>and at a distance of nine hundred kilometers, were not

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<v Speaker 1>perceptible during the day. At night, however, they continued to

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<v Speaker 1>be received by both systems until the port of Karnstadt

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<v Speaker 1>was reached, when only the magnetic detector responded, and that

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<v Speaker 1>only feebly. The disturbing action of daylight was very marked

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<v Speaker 1>in these tests. Having received an invitation from the Canadian

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<v Speaker 1>government to continue his experiments in Canada, Marconi erected a

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<v Speaker 1>large station at Tablehead on the island of Cape Breton,

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<v Speaker 1>at the mouth of Glace Bay, and thirty eight hundred

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<v Speaker 1>kilometers from Poldew. On December twentieth, nineteen oh two, mister

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<v Speaker 1>Marconi sent the first radiograms across the Atlantic to the

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<v Speaker 1>Kings of England and Italy. Shortly afterward, another station was

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<v Speaker 1>erected at Cape cod in Massachusetts, the distance to the

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<v Speaker 1>Poldu station being thirty two hundred miles or six hundred

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<v Speaker 1>and sixty miles further than the Glace Bay station. On

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<v Speaker 1>January sixteenth, nineteen oh three, a complete radiogram was sent

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<v Speaker 1>by President Roosevelt to the King of England. Professor Fessenden

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<v Speaker 1>commenced in eighteen ninety seven the development of the system,

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<v Speaker 1>which is now the property of the National Electric Signaling Company.

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<v Speaker 1>For two years he was engaged by the United States

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<v Speaker 1>Government for special research in the subject, and had the

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<v Speaker 1>advantages of all the resources of a government department at

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<v Speaker 1>his command. His inventions are very numerous and in many

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<v Speaker 1>respects original, and his results show a precision and a

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<v Speaker 1>practicality not attained by many other experimenters in the same field. Magnetic,

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<v Speaker 1>thermal and electrolytic detectors, methods of exact tuning, and even

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<v Speaker 1>wireless telephony are covered by Fessenden's patents. Among these, perhaps

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<v Speaker 1>that which has contributed most to the success of the

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<v Speaker 1>system is the burrider. In its original form, this was

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<v Speaker 1>a thermal receiver depending for its action on the change

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<v Speaker 1>of resistance in a very fine platinum wire when carrying

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<v Speaker 1>the jig current. Latterly, the continuous wire has been discarded

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<v Speaker 1>in favor of an electrolytic coil, one electrode of which

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<v Speaker 1>is an extremely fine point. The apparatus has been described

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<v Speaker 1>more fully under wave detectors. An important feature of this system,

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<v Speaker 1>which greatly aids secrecy of transmission, is the arrangement of

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<v Speaker 1>the sending key, which does not break the circuit, but

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<v Speaker 1>merely alters the wavelength of the waves given out by

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<v Speaker 1>cutting out some inductance. Thus, unless a receiving station is

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<v Speaker 1>tuned with extreme accuracy to the transmitter, it will receive

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<v Speaker 1>instead of signals, only a long continuous dash. Hence, only

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<v Speaker 1>a very sharply tuned receiver will receive a message at all.

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<v Speaker 1>In the latest forms of apparatus, the difference in frequency

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<v Speaker 1>between the waves sent out during spaces and those sent

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<v Speaker 1>as signals is only one quarter percent. Interception by rivals

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<v Speaker 1>is therefore almost impossible. Festenden is apparently the first to

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<v Speaker 1>use an aerial consisting of a steel tube standing on

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<v Speaker 1>an insulating foundation and held in position in insulated stays.

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<v Speaker 1>The following guarantees are made for the festened In system

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<v Speaker 1>by the holding company. Guarantee for a distance one kilowat

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<v Speaker 1>set two hundred fifty miles, five kilowat sets four hundred miles,

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<v Speaker 1>twenty kilood sets seven hundred to seven hundred and fifty miles.

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<v Speaker 1>Guarantee for the prevent used to prevent other sending stations

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<v Speaker 1>from interfering with the receipt of messages. Where the distance

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<v Speaker 1>of the interfering station from the receiving station is more

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<v Speaker 1>than one percent of the distance between the sending and

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<v Speaker 1>receiving stations, a difference in wavelength of three percent is

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<v Speaker 1>sufficient to cut out the interference without the signals being

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<v Speaker 1>appreciably weakened, interfering and sending stations being of equal power.

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<v Speaker 1>Guarantee for the secrecy center. With our latest form of

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<v Speaker 1>secrecy center, the variation in wavelength is guaranteed to be

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<v Speaker 1>only one quarter percent between space and dots. We guarantee

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<v Speaker 1>that no other system can read the messages. Guarantee for

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<v Speaker 1>wave measurer. We guarantee this device to be capable of

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<v Speaker 1>detecting difference of wavelength of one quarter percent, and to

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<v Speaker 1>be capable of measuring wavelengths at a distance from the

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<v Speaker 1>sending station. There are also devices whereby atmospheric discharges will

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<v Speaker 1>not interfere with reception, and a device for modifying the

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<v Speaker 1>intensity of emitted waves without altering their length communicate with

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<v Speaker 1>nearby stations. A report giving a description of the fasten

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<v Speaker 1>In system as applied to transatlantic signaling between Massachusetts and

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<v Speaker 1>Scotland may be of interest here. The power is developed

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<v Speaker 1>by a boiler engine alternator equipment having a maximum capacity

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<v Speaker 1>of twenty five kilowatts sixty cycles current. A transformer steps

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<v Speaker 1>up to the voltage to about twenty five thousand, thus

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<v Speaker 1>charging the condensers, which are discharged by a means of

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<v Speaker 1>a gap adjustable so as to effect the discharge at

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<v Speaker 1>any desired point of the cycle. The receiver used is

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<v Speaker 1>the liquid bretder in its latest form. The aerial is

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<v Speaker 1>formed by a tower extending to a height of four

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<v Speaker 1>hundred and fifteen feet above the ground level and supporting

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<v Speaker 1>a sort of umbrella formed of wires at its top.

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<v Speaker 1>The tower is essentially a steel tube three feet in diameter,

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<v Speaker 1>supported every one hundred feet of its height by a

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<v Speaker 1>set of four steel guys, there being thus sixteen guys

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<v Speaker 1>in all. The tower is pivoted at its base on

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<v Speaker 1>a ball and socket joint and is insulated from the

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<v Speaker 1>ground for a voltage of one hundred and fifty thousand.

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<v Speaker 1>The guys are insulated from the tower as well as

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<v Speaker 1>from the ground. Besides, they are divided into fifty foot

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<v Speaker 1>sections by means of strain insulators. One of the most

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<v Speaker 1>serious problems to be solved was the construction of these

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<v Speaker 1>strain insulators, which, while capable of safely transmitting the maximum

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<v Speaker 1>stress of about twenty thousand pounds, also resist an electrical

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<v Speaker 1>tension of fifteen thousand volts each. The maximum deflection of

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<v Speaker 1>the top of the tower in a ninety mile hurricane

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<v Speaker 1>is computed to be fifteen and a half inches. A

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<v Speaker 1>wave chute, containing over one hundred miles of wire and

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<v Speaker 1>extending over six acres is a very essential feature of

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<v Speaker 1>the installation. On January third, nineteen o six, the first

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<v Speaker 1>signals were received from the American Sex, and shortly afterward

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<v Speaker 1>communication was established so that messages were freely exchanged at night.

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<v Speaker 1>The intensity of the signals received by telephone was at

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<v Speaker 1>times so great that the messages could easily be read

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<v Speaker 1>with the diaphragm three inches from the ears of the operator.

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<v Speaker 1>A station twenty miles distant from Brent Rock, using about

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<v Speaker 1>thirty kilowatts and sending on a wavelength differing not much

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<v Speaker 1>more than three percent from that of the Scottish station,

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<v Speaker 1>was cut out while messages were received from Macrinhanish. A

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<v Speaker 1>system differing in many respects from the other systems has

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<v Speaker 1>been devised by Sir Oliver Lodge and doctor Meirhead. The

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<v Speaker 1>rotating steel disc coherer described under wave detectors is used

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<v Speaker 1>by them. Another feature is the use of two capacity

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<v Speaker 1>areas at both sending and receiving stations, by the adjustment

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<v Speaker 1>of which they may be brought into tune. This system

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<v Speaker 1>has been installed in many places with great success, and

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<v Speaker 1>although it has not yet operated over such distances as

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<v Speaker 1>the US Marconi and Festendon systems, it compares favorably with

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<v Speaker 1>them in syntonizing power and has the advantage of using

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<v Speaker 1>the siphon recorder. The Telefunken system is based on the

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<v Speaker 1>patents of Professor Slabby and Braun and of Count von Arco.

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<v Speaker 1>It may be considered as striking a mean between the

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<v Speaker 1>earlier systems of Marconi and lodgemere Head, though of course

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<v Speaker 1>with many variations and elaborations. In detail, a system of

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<v Speaker 1>wires similar to those used by Marconi forms the aerial

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<v Speaker 1>and the earth connection is given by a large capacity

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<v Speaker 1>as in the lodgemere heead apparatus, A coherer and receiving

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<v Speaker 1>circuit in many respects similar to the Marconi arrangement is employed.

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<v Speaker 1>The DeForest system has had quite an extended commercial application,

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<v Speaker 1>especially in the United States. It has the advantage of

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<v Speaker 1>very rapid signaling twenty five to thirty words per minute

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<v Speaker 1>having been reached. Communication by this system has been established

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<v Speaker 1>between Manhattan Beach, New York and Colon, Panama, a distance

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<v Speaker 1>of two thousand in one hundred and seventy miles. The

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<v Speaker 1>extension of wireless telegraphy and the study of the relations

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<v Speaker 1>of electrical discharges in radioactive bodies bids fair to be

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<v Speaker 1>the most fruitful of the fields of the immediate future.

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<v Speaker 1>The age has been well called the Age of electricity,

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<v Speaker 1>and much amazement, ever, is expressed that man should utilize

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<v Speaker 1>so well a force concerning which he knows so little.

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<v Speaker 1>The complete understanding of the phenomena of atomic force and

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<v Speaker 1>of radioactivity may go far to unlock many of the

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<v Speaker 1>closed doors of nature, and the electrical scientist of today

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<v Speaker 1>is steadily approaching that understanding. End of section thirty two

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<v Speaker 1>and end of the Science History of the Universe, Volume three,

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<v Speaker 1>Physics and Electricity by Francis Rohl Wheeler