CONTENTS FOREWORD. The Modern Conception of Electricity and its Relation to matter and the Ether. CHAPTER I. The growth of electrical signalling systems. Early history of electrical phenomena, the Leyden jar, the growth of electrical signalling systems, earth teturn. The pioneer work of Steinheil, Moise, Wheatstone, Lindsay, and others. CHAPTER II. The development of the telephone. Detailed account of the birth and development of the telephone, including the early discoveries of Reis. A detailed account of the early telephones and work of Bell. Dolbeai's electro-magnetic and electro-static telephones. The capillary telephones of Brtiguet and Plecher. Edison's Eleetromotograph. Preece's hot-wire telephone. The hot-wire telephones of Eccles, Forbes, and Tucker. The Johnson-Guyott system of wireless telegraphy and telephony. The receivers of Brown, Mercadier, Miller, Gaydon, and others. Hughes' pencil microphone. The researches of Johnsen and Rahbek ; their loud speaker and relay. McLachlan's magnetic drum recorder. The " Magnavox." Loud-speakers of Brown, Western Electric Co., and others. The Stentorphone. Unusual methods of telephonic reception. The phenomenon of magnetostrication and Glew's floating magnet. CHAPTER III. First attempts at wireless communication. The work of Loomis. Child's high-tension key. Earth current signalling. The work of Trowbridge, Preece, Rathenau, Willoughby-Smith, and others. Communication with moving trains. The induction methods of Edison, Heaviside, Stevenson, and others. A detailed account of the early work of Hughes ; his discovery and application of electro-magnetic waves before Hertz. Hughes' detectors, microphones, and type- printing telegraph The observations of Edison. Dolbear's wireless system. CHAPTER IV. ElectrO'tnagnetic waves. The discovery of ether waves by Elihu Thomson (12 years before Hertz). The predictions of Clerk Maxwell, Fitzgerald, Helmholtz, and others. The discovery of waves on wires by Von Bezold. The early work of Lodge and others. An account of the discoveries of Hertz. Production, detection, reflection, refraction, polarization and parallel beam radiations of " Hertzian waves ". Lodge's " recoil " and " overflow " effects. The prediction of Crookes. Experiments of Chunder Bose and Righi. CHAPTER V. Wave responding devices of the coherer type. The discovery of electrical coherence by Lodge. The researches of Varley and Onesti on cohesion effects. Minchin's " Impulsion cell " ; details of its construction and use as a detector. Campbell Swinton's voltaic selenium cell. The researches of Minchin and his " seleno-aluminium bridge." The early coherers of Lodge (including his well-known disc coherer), Branly, and others. The anti-coherer of Schafer. The early circuits of Marconi, Popoff, and Dolbear. Self-decohering detectors of Minchin and others. The researches of Jackson, Marconi and others. The coherers of Smith, Ferrie, Blondel, Shoemaker, Pickard, Hughes, Slaby, and others. Popoff's microphonic contact detector. Marconi's first Transatlantic receptions. Tommasina's self-restoring coherer as used by Marconi for first Transatlantic receptions and photograph of same. CHAPTER VI. Magnetic detectors. The work of Rutherford and Wilson. Fessenden's various forms of magnetic wave-responding receivers. The Heterodyne receivers of Fessenden arid Latour. The magnetic or hysteresis detector of Marconi. Braun's magnetic coherer. Saiki's Teppuri detector. The high-frequency receiver of Fessenden. The magnetic- detectors of Walter and Ewing. The Sella-Tieri detector. Marconi's employment of the Einthoven string galvanometer—for high speed reception. Evershed's call relay. CHAPTER VII. Electrolytic and crystal detectors. The evolution of electrolytic detectors including a description of Neugeschwende's detector, de Forest's responder. The positive point electrolytic detectors of Ferrie, Fessenden, Vreeland, Schloemilch, Shoemaker, and Reich. Fessenden's barreter. Tissot's bolometric method of received current measurements, Walter's tantalum detector. The human body as a detector. Brown's peroxide of lead detector. Wichi Torikata's detector. Boy's bouncing jet detector. The development of crystal detectors. Braun's discovery. Dunwoody's first crystal rectifier (catborundum). The researches of Eccles and Braun. The carborundum—mercury detector. An account of the large number of wave-responsive rectifying crystal combinations discovered by Wichi Torikata. Pickard's " perikon " detector. The detectors of Saiki, Lyon, Pierce, Austin, Lepel, and Donle. The "Bronc " cell. Blake's iron-sulphide detector. Eccles' discovery of the oscillating crystal. The experiments with oscillating crystals of Lossev and Podliasky, and Scott-Taggart. Other forms of detector ; de Forest's molecular, the heated thermo-couple, Blake's " hot-point," and Latour's Glow-lamp. The thermal detectors of the N.V.N. and Townsend. Claude's neon detector. Fessenden's frictional receivers. The Poulsen Co.'s " Tikker." Tesla's interrupted receiving circuit. Austin's " rotary tikker." Goldschmidt's " tone wheel." The gas-flame tikker. Also Goldsmith's varying mutual inductance method of recerjtion. CHAPTER VIII. The damn of practical Radio-telegraphy. Lodge's svntonic jars and his application of this fundamentally important discovery to wireless tuning. Marconi's early tuning method. Lodge's " capacity areas." Inductive coupling, disc coherer. Employment of rectifying valves, Muirhead's coherer. Lodge-Muirhead portable aerials, Automatic signalling devices, etc. Marconi, the World's long distance record maker and breaker ; a short account of his early work, his jiggers, early short wave transmitters, etc. Slaby's experiments. Marconi's concentric cylinder aerial. Eccles' early researches and methods of testing coherers, plotting their characteristics, etc. Eccles' thermophone. Fleming's historic first Transatlantic transmissions from Poldhu, and Marconi's reception of same at Newfoundland. A description of many early tests. The origin of the S.O.S. call. Historic occasions of life-saving at sea. CHAPTER IX. Further investigations. The work of Orling and Armstrong. Lippmann's capillary voltmeter. A surface tension experiment. The " Armorl " capillary detectors. Orling's jet relays. Walter's electrolytic relay. The Johnson-Guyott system. Atmospheric disturbances and observations of long distance transmissions. The work of Lodge, Popoff, Feriyi, Turpain, Eccles, Fleming, Marconi, Airey, Appleton, Watt, Marchant, and many others. A brief account of the life and early work of Nikola Tesia, the phenomena of " Stationary waves " on the earth, or " World waves," and his suggestions for the wireless transmission of power, etc. The Marconi " Multiple tuner." CHAPTER X. The employment of ether waves of shorter wavelength than those discovered by Herts, for Radio telegraphy and telephony. Heliography. Mance's Heliograph. The Heliographs of Atkinson, Drummond, and Begbie. Use of the Heliograph during the Boer War. The photophone !—May's discovery of the photo-electrical properties of Selenium. A brief account of the researches of Bell and Tainter, their transmitters and receivers. Mercadier's photo- phone reproducer. The magnetic photophone receiver. The work of Jamieson with a manometric flame. Bell and Hayes photophonic control of a D.C. arc. The speaking arcs of Simon, Reich, and Ruhmer. Duddell's speaking arc. Blake's method of arc modulation. Simon's microphonic arc. Philip Thomas's glow discharge microphone. Manometric flame controllers of Blondel and Chambers. The flame audion, De Forest's gas flame microphone. Further experiments in photophony by Riihmer, Schuckert, Furet, Rankine, and Bragg. Blake's Photophone ; the employment of glass and silica rods to transmit light to selenium cell, etc. Amplification circuits. Blake's method of control of high and low frequency oscillating circuits by means of visible light, and heterodyne method of amplification. Employment of light controlled circuits for naval, military, and many other purposes including star transits, television, photometric measurements, etc. Information re the selenium cell, monochromatic cell, Thalofide cell, antimony sulphide cell, copper oxide cell, also the photo-electric cells of Elster and Geitel, Stebbins, Greigcr, Murdock, and others. The " Polyphos " light sensitive cell. The Rubidium cell, etc. Secret photophonic transmissions. The Larsson and Svalling light-operated relay. The " Photographophone." Blake's prediction and its close fulfilment. The " Pallophotophone." De Forest's " Phonofilm." The Faraday effect. The Kerr effect. The Zeeman effect. The utilization of ultra-violet rays for Radio-telegraphy. The ultra-violet detectors of Zickler and Sella. War-time ultra- violet signalling in England and America. Description of various signalling lamps and methods. Heinicke's method of X-ray telephony. Blake's application of X-rays to radiography of wireless apparatus. Infra-red signalling, Case's method of Harbour defence. Charbonneau's detector for infra-red radiations. Submarine signalling with ultra-sonic sound waves. Piezo-electric properties of quartz and other substances Cady's quartz wavelength standards. Control of frequency at transmitting stations by quartz crystals.

CHAPTER XI. Spark and Arc generators of high-frequency currents. Defines the phenomena of arc and spark generators. Davy's first arc. Spark transmitters. Elihu Thomson's magnetic blow-out. Maiconi's mushroom-shaped electrodes. Parallel straight-edge gap. Dubilier's straight-edge quenched spark gap. Child's spark gap. Fleming's spark discharger. Stone's multiple ball exciter. Duddell's musical arc. The work of Lecher, Peuckert, and Poulsen. Koepsel's arc telephony experiments. Campo's arc modulation method. Eisenstein's method. The work of Majorana. Acceleration of sparking rates, including the work of Fessenden, Eisenstein, Riihmer, ^'ussbaumer, Mosler, Simon, Reich, and others. Wien's quenched spark investigations. The " airblast " spark gaps of Lowenstein, Massie, Fleming, Richardson, and Shaw. Koehler's spark gap. The lotary spark gaps of Tesla, Marconi, Balsillie, and Fessenden. Marconi's rotary disc discharger. The rotary spark gaps of Ducretet and Dubilier. The quenched sparks of the Telefunken Co. and Lepel. The dischargers of Peukert, Fleming, and Dyke. The rotary disc discharger of Lodge and Chambers. Wien's quenching tubes. Chaffee's quenched spark and Washington's modification thereof. Ditcham's spark gap. De Forest's Tungsten gap. The T.Y.K. gap. The Moretti derlagrator. Jackson's C.W. generator. Dwyer's arc. Investigations of sparks in liquids, by Eccles and Makower. Dubilier's rotating gap and description of his system. Parallel cylinder spark gap of La Compagnie GeneYale de Radio-t^legraphie, Thieme, Fessenden, and Coursey.

CHAPTER XII. The multiple arc, hydrogen arc, mercury vapour, and some other methods of producing high-frequency oscillations. Duddell's 1900 discoveries. Arcs in series in air. Poulsen's arc in hydrogen. Elihu Thomson's magnetic blast. The Author's 1913 experiments. A 25 KW. arc. Pedersen and Poulsen's arc connections. Employment of vaporized spirit by Scheller. Poulsen's gas flame arc. Brown's C.W. generator. Arc method of producing low-frequency oscillations. The Magunna converter. Schwerin's method of generating constant current. The arc generators of Fleming, Colin and Jeance, Jahnke, de Forest, Dubilier, and Huth. Riihmer's aluminium arc. The mercury vapour oscillators of Cooper-Hewitt, Simon and Reich, Liebonwitz, Vreeland, and La Society Fran^aise. The " Pointolite " lamp as a aource of H.F. oscillations. Marconi's high-speed rotating disc discharger and variations of its construction and applications. Coursey's rotary spark gap. Marconi's synchronous disc discharger. Marconi's achievement in signalling round the World in 1918 with his " timed disc." Majoiana's rotary gap. Ferri^'s rotary discharger. Fessenden's capacity changer. CHAPTER XIII. Various types of Microphone. Early types of microphone. The microphones of Berliner, Rlake, Edison, Hunnings. The G.P.O. solid-back microphone. The microphones of Fessenden and Collins. Dubilier's water-cooled relay microphone (or " repeater "). Fessenden's telephone relay. Goldschmidt's parallel microphones The liquid microphones of Jervis-Smith, Vanni, and Majorana. Chichester Bell's sound sensitive jet. The liquid microphones of Sykes and Ford, and of Chambers. Fessenden's condenser microphone. Burstyn's multiple condenser microphone. Western Electric condenser Microphone. Alexanderson's magnetic microphone relay. Coursey's mercury vapour modulator. The Marconi-Sykes-Round magnetic microphone. Tucker's hot-wire microphone, and the Author's suggestion for its employment in Radio reception. Koepsel's relay. Microphonic relays. Lodge's telegraphic relay. Fessenden's differential telephone relay. Brown's telephone relay. Tuned microphonic relay. Majorana's relays. The flame amplifier. De Forest's microphonic flame experiments. CHAPTER XIV. The Work of R. A. Fessenden. Methods of recording transmissions of photographs. Experiments in television. Radio-dynamic control, etc. An account of Fessenden's achievement in linking up land line telephones with wireless in 1906. Fessenden's interference preventer, and " heterodyne " beat reception. The inception of the London Wireless Society, and its expansion into the Radio Society of Great Britain. The photographic methods of recording signals of Campbell Swinton, McNamara, etc. Fessenden's dictaphonic method of recording, its employment by Scott for instructional purposes. The Author's experiments in dictaphonic reception and retransmission of telephony. The " Photographophone." Poulsen's " Telegraphone." Pedersen's telegraphonic reception of two messages simultaneously. Poulsen's improved telegraphones. Winkler's " Siphon " recorder. Bront's mechanical relay. Powell's radium recording device. Another simple microphonic relay. Cox's selenium amplifier. Other methods of recording. Creed's method of automatic transmission, and reception and reproduction in Roman type. The automatic transmitters of Lodge-Muirhead, Westhead, Pedersen, etc. Duplex and multiplex Radio-telegraphy and telephony. Fessenden's method. Marconi's disc discharger method. Eccles' suggestion of the employment of directive aerials. The Marconi Co.'s balancing aerial method. The work of Poulsen, the G.P.O., the Marconi Co., the Radio Corporation of America, and others. Duplex and multiplex systems. Tesla and others suggest time signals. The work of Ferri6 at the Eiffel Tower. American and German time signals. Radio-teleinscription. Wireless transmission of photographs. The " pantelegraph." The systems of Belin, Korn, Knudsen, Thome Baker, Waltz and Meusser, and Andersen. American pictographic transmissions. Radio transmissions of pictures by the Marconi Co., and the Radio Corporation of America, from England to America in 1924. Maskelyne's method of transmitting and reproducing pictures by code. Television. Campbell Swinton's suggested method. The experiments of Langer, Baird, and others. Radio-dynamic control. Branly's early experiments. Methods of, wireless control of torpedo boats of Devaux, Martin, etc. Raymond's airship control. The radio ship control methods of Dolme-Dehan, Abraham, and Chauveau. Radio- control in warfare, G. de Trarrazaval's method. Experiments by the French Signal Corps. Successful French Government tests at Etampes in 1921 with radio controlled aircraft. Prediction of practical applications. Motor-car controlled by wireless. Webb's method of Radio control. Radio control of massive machinery. Submarine wireless. Communication between aeroplanes in flight. The " Variometer " and its development from the Ayrton-Perry variable " self-inductance standard." The Variometers of the Amalgamated Radio-telegraph Co., the Telefunken Co., Eisenstein and the modern variometer. High-frequency alternators of Fessenden, Alexanderson, Franklin, Bethenod, Bouthillon, Latour, Taylor, and others. Goldschmidt's reflection alternator. The triple frequency raiser of Korda. Pedersen's frequency raiser. Static frequency raisers of Epstein, Latour, Valauri, Joly, Taylor, Kujirai, Spinelli, Schoenberg, and others. Frequency raisers employing valves, mercury vapour lamps, electrolytic or other means of rectification :—Zenneck's frequency doubler. Franklin's frequency raiser. Frequency raisers for reception :—as suggested by Scott-Taggart and others. Bardeloni's method of separating radio signals of the same wavelength and for the reduction of static interference. CHAPTER XV. The Thermionic Valve and some of the fundamental valve circuits. De Forest's discovery that heated gas molecules were sensitive to H.F. oscillations, and his gas flame detector. The Edison effect. The researches of Preece, Fleming, and J. J- Thomson. Fleming's " Edison effect " in air. The Fleming " arc effect." Fleming's 2-electrode valve, and tungsten filaments. De Forest's molecular detector. Latour's mercury vapour amplifier. The 3-electrode valve. De Forest's " Audion." Stanlev's ready method of testing the vacuum of a valve. Von Lieben's 3-electrode valve.' The Lieben-Reiz " gas relay." Arco and Meissner patents for relaying and amplifying. Round's valve constructional patents, multi-filaments, etc. The French " R " valve, other " R " valves. Marconi's Co.'s Q valve. German valves. Round's grid condenser and resistance. Employment of valves in parallel, and " oil jacket " cooling. Weagent's 3-electrode valve having exterior electro-static control. Round's valve having exterior magnetic control. Weagent's valve with central filament connection. The " Sodion " detector valve, the Thermagnion, Hull's Magnetron, Langmuir's hard valves, the Pliotron, and the Kenotron. The Holweck valve. Silica valves. Hull's dynatron. Valves with more than three electrodes :—the 4-electrode valve of Arco and Meissner. Hull's Pliodynatron. Fleming's 4-electrode valve. The variable anode tap. The double grid valve of the Western Electric Co. Scott-Taggart's 4-electrode valve. Anode heating control method of the German Wireless Telegraph Co. The Negatron. The 5-electrode valves of the Marconi Co., de Forest, and Brackett. Alexanderson's 6-electrode valve. Dull emitter valves. The coated filaments of Wehnelt, Coolidge, and Langmuir. The Thermion Vacuumless valve. The phototron. Valve circuits :—De Forest's "Ultrau- dion." The regenerative or " feed back " circuits of de Forest, Armstrong, and Meissner. Litigation in America. Round's " Autodyne " method and circuits, and neutralization of valve capacity. Weagent's reaction circuit. Armstrong's super-regenerative circuits. The work of Bolitho and Turner. Armstrong's " tuned plate " circuit. Johnston's " tuned cathode " circuit. Armstrong's combined audio and radio frequency re- generative method. Armstrong's electro-static grid plate coupling. " Hard valve " characteristics and circuits. The Turner valve relay. Flewelling's super-regenerative circuit. Blake's flame grid leak. Flewelling's simplified super-circuit. The Blake- Flewelling circuit. Fessenden's separate heterodyne method, homodyne reception. Capacity resistance coupled amplifiers. Aimstrong's super-sonic heterodyne method. Houck's super-heterodyne circuit. The Tropadyne circuit. Thompson's reflex circuit. The reflex circuits of Latour and Armstrong. The S.T. 100 circuit. Scott-Taggart's ' Resistoflex " circuit. Audio-frequency reaction. Push and pull amplifier. Scott- Taggart's grid to plate amplifier. Impedance coupled power amplifier. Round's neutralization of grid and plate capacity. Wright's neutralization method. Hazeltine's neutiodyne circuit. Stabilizers. Hazeltine's 5-valve neutrodyne circuit. " Unidyne " reception (with 4-electrode and with 3-electrode valves). Electrolytic amplifiers. The Reinartz tuner ; and with one stage of H.F. amplification. Reinartz transmitter. The Hartley circuit. Methods of interference prevention including Marconi's " X " stopper. Fessenden's interference preventer. The aperiodic shields of Pickard and Dieckmann. Levy's filter circuit. The loop aerial methods of Pickard and Tavlor. The Bellescize differential method. The balanced aerial method. The methods of Austin and CharTee. Round's balanced crystal method. Wright's interference limiter. Dimmed valve limiter. 4-electrode valve limiter. Turner's Kallirotron limiter. CharTee's interference limiter. Hinton'a interference preventer. Simple rejector circuits. The Autoveyor's 3-electrode condenser. Radio-telephonic modulation. Fessenden's early work. Valve transmitter modulation. The work of Round and his intermediate circuit control method. The methods of Langmuir. Shunted inductance method. Grid circuit modulation. Prince's choke control. Resistance control. Coursey's saturated valve and shunt control methods. Quiescent aerial modulation. Round's method of telephony from spark coil supply. Communication between British Isles and Australia by the Marconi Co. with valve transmitters in 1921. 56-valve panel at Carnarvon. Marconi Co, telephone by radio to Sydney in 1924. Short wave transmissions.

CHAPTER XVI. Direction finding, etc. The early work of Brown, Elihu Thomson, and Stone. The work of Braun, Artom. and Marconi. The frame aerials of de Forest. Braun employs frame aerial for trans- missions. Pickard maps out wave front round a transmitting station, and his discovery that wave front was tilted forward. German method of correcting for wave front inclination errors. The work of Admiral Jackson. The Bellini-Tosi Radiogoniometer The Marconi Bellini-Tosi compass. The Telefunken wireless compass. The Marconi compass. Fessenden's directional aerials. The buried condenser and low aerial methods of Hanson and Jones. U.S. Navy radio compass. Radio-Lighthouses. " Radiophares." De Forest's " Aerophores " The methods of direction finding of Robinson, Erskine-Murray, Round, Frost, Van de Velde, and Furnival. Horton's method of predetermining position for D.F. apparatus when building ships. Swinton's experiments with shielded frame aerials. Taylor's directional system. Blondet's D.F. receiver and recorder. The experiments of Gouraud in screening from direction finders. The multiple direction finder. Earth antennae and low aerials. The work of Braun, Kiebitz, and Hall. The Beverage aerial. Signalling with buried antennas. Work of Murgas and Rogers. Hall's method. The Author's method of reception without aerials. Ionized beam aerials and conductors. The Author's ionization experi- ments and triode valve electroscope. Permanent electrification. Short wave directional wireless. The methods of Marconi and Franklin. Experiments at Carnarvon ; also between Hendon and Birmingham. The Inchkeith revolving reflector. Franklin's demonstration at the I.E.E. The early work of Marconi, Brown, and de Forest. " Beam Wireless." Short wave duplex Radio-telephony between England and Holland. Variometer for short wave transmission. The calling up devices of the Marconi Co. The Turner-Shephard-Lee call device. Fleming's call device. The condenser operated call device of the Radio Communication Co. " Slipping Thread " call relay. Neon tube call device. Fleming's neon tube. Production of electrical impulses by neon tubes. The " Osglim "lamp and its application to wireless. The Anson neon tube relay. The Dowling " zero shunt " circuit. Blake's adaptation of the " zero shunt " for recording. Transatlantic radio telephony by " side band " method. The " side band " system. " Wired wireless." The early work of Edison, Leblanc, Turpain, Rvihmer, Squier and Erskine-Murray. The "Ducon." The work of the Western Electric Co. in America. The Geman Telegraphen Versuchsamt Riibmer's multiplex system. The methods of Huth, Rosenbaum, Loewe, and Muirhead. Prince's electro-capillary call device for " wired wireless." The B.B.C. " wired wireless " achievement in 1922. Modern earth current signalling. The work of Col. Ferrie\ Brown, The Deutsche Teiephonwerke, and de Forest. A detailed account of the first amateur Transatlantic Tests, under the auspices of the Radio Society of Great Britain. The first Receptions in England from America. The first transmissions from England received in America. French and American amateurs get into touch by radio. Amateur Transworld Tests. Symonds com- municates with Bell in New Zealand (the longest possible distance on eaith). Trans- atlantic telephony from Rugby.

APPENDIX. APPENDIX A. Extracts from a paper by the Author, to the Radio Society of Great Britain, describing his mechanical model of a 3-electrode valve for instructional purposes,

APPENDIX B. A description of R. C. Clinker's Dynamic model of a transmitting valve as described by him in a lecture to the Wireless Section of the Institution of Electrical Engineers. Reference is also made to E. W. Marchant's coupled circuit model and the Author's suggestion of a further extension of Clinker's model to include a mechanical illustration of the Neutrodyne principle. APPENDIX C. Three circuits due to W. H. Eccles and shown by him at two lectures delivered at the Royal Institution of Great Britain : (A) The first D.C. motor without sliding contacts. (B) Eccles' tuning fork controlled valve circuit, and its application to control of frequencies at a transmitting station. Also the use of quartz crystals for control of transmitting frequencies. (C) Eccles experiment in which a 2-electrode valve controls the oscillations of, and keeps in step with, a free pendulum.

APPENDIX D. The Lodge-Robinson " N " circuit and the tuning method of Melinsky.