Journal of Physics

SUBJECT AREA: Electricity

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Joubert became Professor of Physics in the Collège Rollin, Paris, in 1874, a position he held until 1888. He was at one time General Secretary of the Société Française de Physique. In collaboration with Pasteur he began studies into the theories of germs and bacteria. In 1880 Joubert carried out research on wave-forms in alternating-current arc-lighting circuits. Reinventing a method previously used by earlier experimenters, including Wheatstone, he was, by a mechanical sampling technique, able to determine the voltage at different points in the cycle. By using a rotating contact on the alternator shaft, the angular position of which could be varied, the whole of the wave-form could be delineated. This successful technique was widely used for some thirty years.

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See also: Duddell, William du Bois

SUBJECT AREA: Broadcasting, Telecommunications

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After early ambitions to become a professional cricketer, Appleton went to St John's College, Cambridge, where he studied under J.J.Thompson and Ernest Rutherford. His academic career interrupted by the First World War, he served as a captain in the Royal Engineers, carrying out investigations into the propagation and fading of radio signals. After the war he joined the Cavendish Laboratory, Cambridge, as a demonstrator in 1920, and in 1924 he moved to King's College, London, as Wheatstone Professor of Physics.

In the following decade he contributed to developments in valve oscillators (in particular, the "squegging" oscillator, which formed the basis of the first hard-valve time-base) and gained international recognition for research into electromagnetic-wave propagation. His most important contribution was to confirm the existence of a conducting ionospheric layer in the upper atmosphere capable of reflecting radio waves, which had been predicted almost simultaneously by Heaviside and Kennelly in 1902. This he did by persuading the BBC in 1924 to vary the frequency of their Bournemouth transmitter, and he then measured the signal received at Cambridge. By comparing the direct and reflected rays and the daily variation he was able to deduce that the Kennelly- Heaviside (the so-called E-layer) was at a height of about 60 miles (97 km) above the earth and that there was a further layer (the Appleton or F-layer) at about 150 miles (240 km), the latter being an efficient reflector of the shorter radio waves that penetrated the lower layers. During the period 1927–32 and aided by Hartree, he established a magneto-ionic theory to explain the existence of the ionosphere. He was instrumental in obtaining agreement for international co-operation for ionospheric and other measurements in the form of the Second Polar Year (1932–3) and, much later, the International Geophysical Year (1957–8). For all this work, which made it possible to forecast the optimum frequencies for long-distance short-wave communication as a function of the location of transmitter and receiver and of the time of day and year, in 1947 he was awarded the Nobel Prize for Physics.

He returned to Cambridge as Jacksonian Professor of Natural Philosophy in 1939, and with M.F. Barnett he investigated the possible use of radio waves for radio-location of aircraft. In 1939 he became Secretary of the Government Department of Scientific and Industrial Research, a post he held for ten years. During the Second World War he contributed to the development of both radar and the atomic bomb, and subsequently served on government committees concerned with the use of atomic energy (which led to the establishment of Harwell) and with scientific staff.

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SUBJECT AREA: Electricity, Telecommunications

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After graduating from University College, London, Ayrton became for a short time a pupil of Sir William Thomson in Glasgow. For five years he was employed in the Indian Telegraph Service, eventually as Superintendent, where he assisted in revolutionizing the system, devising methods of fault detection and elimination. In 1873 he was invited by the Japanese Government to assist as Professor of Physics and Telegraphy in founding the Imperial College of Engineering in Tokyo. There he created a teaching laboratory that served as a model for those he was later to organize in England and which were copied elsewhere. It was in Tokyo that his joint researches with Professor John Perry began, an association that continued after their return to England. In 1879 he became Professor of Technical Physics at the City and Guilds Institute in Finsbury, London, and later was appointed Professor of Physics at the Central Institution in South Kensington.

The inventions of Avrton and Perrv included an electric tricycle in 1882, the first practicable portable ammeter and other electrical measuring instruments. By 1890, when the research partnership ended, they had published nearly seventy papers in their joint names, the emphasis being on a mathematical treatment of subjects including electric motor design, construction of electrical measuring instruments, thermodynamics and the economical use of electric conductors. Ayrton was then employed as a consulting engineer by government departments and acted as an expert witness in many important patent cases.

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SUBJECT AREA: Broadcasting, Electronics and information technology

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Ives gained his PhD in physics from Johns Hopkins University, Baltimore, Maryland, and subsequently served in the US Signal Corps, eventually gaining experience in aerial photography. He then joined the Western Electric Engineering Department (later Bell Telephone Laboratories), c.1920 becoming leader of a group concerned with television-image transmission over telephone lines. In 1927, using a Nipkow disc, he demonstrated 50-line, 18 frames/sec pictures that could be displayed as either 2 in.×2 1/2 in. (5.1 cm×6.4 cm) images suitable for a "wirephone", or 2 ft ×2 1/2 ft (61 cm×76 cm) images for television viewing. Two years later, using a single-spiral disc and three separately modulated light sources, he was able to produce full-colour images.

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See also: Baird, John Logie; Jenkins, Charles Francis

SUBJECT AREA: Broadcasting, Electronics and information technology, Telecommunications

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Popov, the son of a village priest, received his early education in a seminary, but in 1877 he entered the University of St Petersburg to study mathematics. He graduated with distinction in 1883 and joined the faculty to teach mathematics and physics. Then, increasingly interested in electrical engineering, he became an instructor at the Russian Navy Torpedo School at Krondstadt, near St Petersburg, where he later became a professor. On 7 May 1895 he is said to have transmitted and received Morse code radio signals over a distance of 40 m (130 ft) in a demonstration given at St Petersburg University to the Russian Chemical Society, but in a paper published in January 1896 in the Journal of the Russian Physical and Chemical Society, he in fact described the use of a coherer for recording atmospheric disturbances such as lightning, together with the design of a modified coherer intended for reception at a distance of 5 km (3 miles). Subsequently, on 26 November 1897, after Marconi's own radio-transmission experiments had been publicized, he wrote a letter claiming priority for his discovery to the English-language journal Electrician, in the form of a translated précis of his original paper, but neither the original Russian paper nor the English précis made specific claims of either a receiver or a transmitter as such. However, by 1898 he had certainly developed some form of ship-to-shore radio for the Russian Navy. In 1945, long after the Russian revolution, the communist regime supported his claim to be the inventor of radio, but this is a matter for much debate and the priority of Marconi's claim is generally acknowledged outside the USSR.

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SUBJECT AREA: Electricity, Metallurgy

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Coolidge obtained his BS from the Massachusetts Institute of Technology (MIT) in 1896, and his PhD (physics) from the University of Leipzig in 1899. He was appointed Assistant Professor of Physics at MIT in 1904, and in 1905 he joined the staff of the General Electric Company's research laboratory at Schenectady. In 1905 Schenectady was trying to make tungsten-filament lamps to counter the competition of the tantalum-filament lamps then being produced by their German rival Siemens. The first tungsten lamps made by Just and Hanaman in Vienna in 1904 had been too fragile for general use. Coolidge and his life-long collaborator, Colin G. Fink, succeeded in 1910 by hot-working directly dense sintered tungsten compacts into wire. This success was the result of a flash of insight by Coolidge, who first perceived that fully recrystallized tungsten wire was always brittle and that only partially work-hardened wire retained a measure of ductility. This grasped, a process was developed which induced ductility into the wire by hot-working at temperatures below those required for full recrystallization, so that an elongated fibrous grain structure was progressively developed. Sintered tungsten ingots were swaged to bar at temperatures around 1,500°C and at the end of the process ductile tungsten filament wire was drawn through diamond dies around 550°C. This process allowed General Electric to dominate the world lamp market. Tungsten lamps consumed only one-third the energy of carbon lamps, and for the first time the cost of electric lighting was reduced to that of gas. Between 1911 and 1914, manufacturing licences for the General Electric patents had been granted for most of the developed work. The validity of the General Electric monopoly was bitterly contested, though in all the litigation that followed, Coolidge's fibering principle was upheld. Commercial arrangements between General Electric and European producers such as Siemens led to the name "Osram" being commonly applied to any lamp with a drawn tungsten filament. In 1910 Coolidge patented the use of thoria as a particular additive that greatly improved the high-temperature strength of tungsten filaments. From this development sprang the technique of "dispersion strengthening", still being widely used in the development of high-temperature alloys in the 1990s. In 1913 Coolidge introduced the first controllable hot-cathode X-ray tube, which had a tungsten target and operated in vacuo rather than in a gaseous atmosphere. With this equipment, medical radiography could for the first time be safely practised on a routine basis. During the First World War, Coolidge developed portable X-ray units for use in field hospitals, and between the First and Second World Wars he introduced between 1 and 2 million X-ray machines for cancer treatment and for industrial radiography. He became Director of the Schenectady laboratory in 1932, and from 1940 until 1944 he was Vice-President and Director of Research. After retirement he was retained as an X-ray consultant, and in this capacity he attended the Bikini atom bomb trials in 1946. Throughout the Second World War he was a member of the National Defence Research Committee.

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SUBJECT AREA: Broadcasting, Electronics and information technology, Photography, film and optics, Recording, Telecommunications

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De Forest was born into the family of a Congregational minister that moved to Alabama in 1879 when the father became President of a college for African-Americans; this was a position that led to the family's social ostracism by the white community. By the time he was 13 years old, De Forest was already a keen mechanical inventor, and in 1893, rejecting his father's plan for him to become a clergyman, he entered the Sheffield Scientific School of Yale University. Following his first degree, he went on to study the propagation of electromagnetic waves, gaining a PhD in physics in 1899 for his thesis on the "Reflection of Hertzian Waves from the Ends of Parallel Wires", probably the first US thesis in the field of radio.

He then joined the Western Electric Company in Chicago where he helped develop the infant technology of wireless, working his way up from a modest post in the production area to a position in the experimental laboratory. There, working alone after normal working hours, he developed a detector of electromagnetic waves based on an electrolytic device similar to that already invented by Fleming in England. Recognizing his talents, a number of financial backers enabled him to set up his own business in 1902 under the name of De Forest Wireless Telegraphy Company; he was soon demonstrating wireless telegraphy to interested parties and entering into competition with the American Marconi Company.

Despite the failure of this company because of fraud by his partners, he continued his experiments; in 1907, by adding a third electrode, a wire mesh, between the anode and cathode of the thermionic diode invented by Fleming in 1904, he was able to produce the amplifying device now known as the triode valve and achieve a sensitivity of radio-signal reception much greater than possible with the passive carborundum and electrolytic detectors hitherto available. Patented under the name Audion, this new vacuum device was soon successfully used for experimental broadcasts of music and speech in New York and Paris. The invention of the Audion has been described as the beginning of the electronic era. Although much development work was required before its full potential was realized, the Audion opened the way to progress in all areas of sound transmission, recording and reproduction. The patent was challenged by Fleming and it was not until 1943 that De Forest's claim was finally recognized.

Overcoming the near failure of his new company, the De Forest Radio Telephone Company, as well as unsuccessful charges of fraudulent promotion of the Audion, he continued to exploit the potential of his invention. By 1912 he had used transformer-coupling of several Audion stages to achieve high gain at radio frequencies, making long-distance communication a practical proposition, and had applied positive feedback from the Audion output anode to its input grid to realize a stable transmitter oscillator and modulator. These successes led to prolonged patent litigation with Edwin Armstrong and others, and he eventually sold the manufacturing rights, in retrospect often for a pittance.

During the early 1920s De Forest began a fruitful association with T.W.Case, who for around ten years had been working to perfect a moving-picture sound system. De Forest claimed to have had an interest in sound films as early as 1900, and Case now began to supply him with photoelectric cells and primitive sound cameras. He eventually devised a variable-density sound-on-film system utilizing a glow-discharge modulator, the Photion. By 1926 De Forest's Phonofilm had been successfully demonstrated in over fifty theatres and this system became the basis of Movietone. Though his ideas were on the right lines, the technology was insufficiently developed and it was left to others to produce a system acceptable to the film industry. However, De Forest had played a key role in transforming the nature of the film industry; within a space of five years the production of silent films had all but ceased.

In the following decade De Forest applied the Audion to the development of medical diathermy. Finally, after spending most of his working life as an independent inventor and entrepreneur, he worked for a time during the Second World War at the Bell Telephone Laboratories on military applications of electronics.

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KF / JW

SUBJECT AREA: Electronics and information technology

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Born on a cattle ranch, Forrester obtained a BSc in electrical engineering at the University of Nebraska in 1939 and his MSc at the Massachusetts Institute of Technology (MIT) in Cambridge, Massachusetts, where he remained to teach and carry out research. Becoming interested in computing, he established the Digital Computer Laboratory at MIT in 1945 and became involved in the construction of Whirlwind I, an early general-purpose computer completed in March 1951 and used for flight-simulation by the US Army Air Force. Finding the linear memories then available for storing data a major limiting factor in the speed at which computers were able to operate, he developed a three-dimensional store based on the binary switching of the state of small magnetic cores that could be addressed and switched by a matrix of wires carrying pulses of current. The machine used parallel synchronous fixed-point computing, with fifteen binary digits and a plus sign, i.e. 16 bits in all, and contained 5,000 vacuum tubes, eleven semiconductors and a 2 MHz clock for the arithmetic logic unit. It occupied a two-storey building and consumed 150kW of electricity. From his experience with the development and use of computers, he came to realize their great potential for the simulation and modelling of real situations and hence for the solution of a variety of management problems, using data communications and the technique now known as interactive graphics. His later career was therefore in this field, first at the MIT Lincoln Laboratory in Lexington, Massachusetts (1951) and subsequently (from 1956) as Professor at the Sloan School of Management at the Massachusetts Institute of Technology.

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See also: Burks, Arthur Walter; Goldstine, Herman H.; Wilkes, Maurice Vincent; Williams, Sir Frederic Calland

SUBJECT AREA: Metallurgy

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Hunter arrived in England in 1902, the seventh in the succession of New Zealand students nominated for the 1851 Exhibition science research scholarships (the third, in 1894, having been Ernest Rutherford). He intended to study the metallurgy of tellurides at the Royal School of Mines, but owing to the death of the professor concerned, he went instead to University College London, where his research over two years involved the molecular aggregation of liquified gases. In 1904–5 he spent a third year in Göttingen, Paris and Karlsruhe. Hunter then moved to the USA, beginning work in 1906 with the General Electric Company in Schenectady. His experience with titanium came as part of a programme to try to discover satisfactory lamp-filament materials. He and his colleagues achieved more success in producing moderately pure titanium than previous workers had done, but found the metal's melting temperature inadequate. However, his research formed the basis for the "Hunter sodium process", a modern method for producing commercial quantities of titanium. In 1908 he was appointed Assistant Professor of Electrochemistry and Physics at Rensselaer Polytechnic Institute in Troy, New York, where he was to remain until his retirement in 1949 as Dean Emeritus. In the 1930s he founded and headed the Institute's Department of Metallurgical Engineering. As a consultant, he was associated with the development of Invar, Managanin and Constantan alloys.

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SUBJECT AREA: Mechanical, pneumatic and hydraulic engineering

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Educated at Queens College, Belfast, Perry became Physics Master at Clifton College in 1870 until 1874. This was followed by a brief period of study under Sir William Thomson in Glasgow. He was then appointed Professor of Engineering at the Imperial College of Japan in Tokyo, where he formed a remarkable research partnership with W.E. Ayrton. On his return to England he became Professor of Engineering and Mathematics at City and Guilds College, Finsbury. Perry was the co-inventor with Ayrton of many electrical measuring instruments between 1880 and 1890, including an energy meter incorporating pendulum clocks and the first practicable portable ammeter and voltmeter, the latter being extensively used until superseded by instruments of greater accuracy. An optical indicator for high-speed steam engines was among Perry's many patents. Having made a notable contribution to education, particularly in the teaching of mathematics, he turned his attention in the latter period of his life to the improvement of the gyrostatic compass.

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SUBJECT AREA: Metallurgy

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His family emigrated to Australia when he was 5 years old. He was educated at Wesley College, Melbourne, and attended Queen's College, University of Melbourne, graduating in physics and engineering in 1897. As an 1851 Exhibitioner he then spent three years at St John's College, Cambridge, under Sir Alfred Ewing, where he studied the microstructure of deformed metal crystals and abandoned his original intention of becoming a civil engineer. Rosenhain was the first to observe the slip-bands in metal crystals, and in the Bakerian Lecture delivered jointly by Ewing and Rosenhain to the Royal Society in 1899 it was shown that metals deformed plastically by a mechanism involving shear slip along individual crystal planes. From this conception modern ideas on the plasticity and recrystallization of metals rapidly developed. On leaving Cambridge, Rosenhain joined the Birmingham firm of Chance Brothers, where he worked for six years on optical glass and lighthouse-lens systems. A book, Glass Manufacture, written in 1908, derives from this period, during which he continued his metallurgical researches in the evenings in his home laboratory and published several papers on his work.

In 1906 Rosenhain was appointed Head of the Metallurgical Department of the National Physical Laboratory (NPL), and in 1908 he became the first Superintendent of the new Department of Metallurgy and Metallurgical Chemistry. Many of the techniques he introduced at Teddington were described in his Introduction to Physical Metallurgy, published in 1914. At the outbreak of the First World War, Rosenhain was asked to undertake work in his department on the manufacture of optical glass. This soon made it possible to manufacture optical glass of high quality on an industrial scale in Britain. Much valuable work on refractory materials stemmed from this venture. Rosenhain's early years at the NPL were, however, inseparably linked with his work on light alloys, which between 1912 and the end of the war involved virtually all of the metallurgical staff of the laboratory. The most important end product was the well-known "Y" Alloy (4% copper, 2% nickel and 1.5% magnesium) extensively used for the pistons and cylinder heads of aircraft engines. It was the prototype of the RR series of alloys jointly developed by Rolls Royce and High Duty Alloys. An improved zinc-based die-casting alloy devised by Rosenhain was also used during the war on a large scale for the production of shell fuses.

After the First World War, much attention was devoted to beryllium, which because of its strength, lightness, and stiffness would, it was hoped, become the airframe material of the future. It remained, however, too brittle for practical use. Other investigations dealt with impurities in copper, gases in aluminium alloys, dental alloys, and the constitution of alloys. During this period, Rosenhain's laboratory became internationally known as a centre of excellence for the determination of accurate equilibrium diagrams.

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SUBJECT AREA: Electricity, Photography, film and optics

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At the age of 14 Swan was apprenticed to a Sunderland firm of druggists, later joining John Mawson who had opened a pharmacy in Newcastle. While in Sunderland Swan attended lectures at the Athenaeum, at one of which W.E. Staite exhibited electric-arc and incandescent lighting. The impression made on Swan prompted him to conduct experiments that led to his demonstration of a practical working lamp in 1879. As early as 1848 he was experimenting with carbon as a lamp filament, and by 1869 he had mounted a strip of carbon in a vessel exhausted of air as completely as was then possible; however, because of residual air, the filament quickly failed.

Discouraged by the cost of current from primary batteries and the difficulty of achieving a good vacuum, Swan began to devote much of his attention to photography. With Mawson's support the pharmacy was expanded to include a photographic business. Swan's interest in making permanent photographic records led him to patent the carbon process in 1864 and he discovered how to make a sensitive dry plate in place of the inconvenient wet collodian process hitherto in use. He followed this success with the invention of bromide paper, the subject of a British patent in 1879.

Swan resumed his interest in electric lighting. Sprengel's invention of the mercury pump in 1865 provided Swan with the means of obtaining the high vacuum he needed to produce a satisfactory lamp. Swan adopted a technique which was to become an essential feature in vacuum physics: continuing to heat the filament during the exhaustion process allowed the removal of absorbed gases. The inventions of Gramme, Siemens and Brush provided the source of electrical power at reasonable cost needed to make the incandescent lamp of practical service. Swan exhibited his lamp at a meeting in December 1878 of the Newcastle Chemical Society and again the following year before an audience of 700 at the Newcastle Literary and Philosophical Society. Swan's failure to patent his invention immediately was a tactical error as in November 1879 Edison was granted a British patent for his original lamp, which, however, did not go into production. Parchmentized thread was used in Swan's first commercial lamps, a material soon superseded by the regenerated cellulose filament that he developed. The cellulose filament was made by extruding a solution of nitro-cellulose in acetic acid through a die under pressure into a coagulating fluid, and was used until the ultimate obsolescence of the carbon-filament lamp. Regenerated cellulose became the first synthetic fibre, the further development and exploitation of which he left to others, the patent rights for the process being sold to Courtaulds.

Swan also devised a modification of Planté's secondary battery in which the active material was compressed into a cellular lead plate. This has remained the central principle of all improvements in secondary cells, greatly increasing the storage capacity for a given weight.

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SUBJECT AREA: Electronics and information technology, Telecommunications

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After attending schools in Palo Alto and Halcyon, Russell Varian went to Stanford University, gaining his BA in 1925 and his MA in 1927 despite illness and being dyslexic. His family being in need of financial help, he first worked for six months for Bush Electric in San Francisco and then for an oil company in Texas, returning to San Francisco in 1930 to join Farnsworth's Television Laboratory. After a move to Philadelphia, in 1933 the laboratory closed and Russell tried to take up a PhD course at Stanford but was rejected, so he trained as a teacher. However, although he did some teaching at Stanford it was not to be his career, for in 1935 he joined his brothers Sigurd and Eric in the setting up of a home laboratory.

There, with William Hansen, a former colleague of Russell's at Stanford, they worked on the development of microwave oscillators, based on some of the latter's ideas. By 1937 they had made sufficient progress on an electron velocity-bunching tube, which they called the klystron, to obtain an agreement with the university to provide laboratory facilities in return for a share of any proceeds. By August that year they were able to produce continuous power at a wavelength of 13 cm. Clearly needing greater resources to develop and manufacture the tube, and with a possible war looming, a deal was struck with the Sperry Gyroscope Company to finance the work, which was transferred to the East Coast.

In 1946, after the death of his first wife, Russell returned to Palo Alto, and in 1948 the brothers and Hansen founded Varian Associates to make microwave tubes for transmitters and linear accelerators and nuclear magnetic-resonance detectors. Subsequent research also resulted in the development of a satellite-borne magnetometer for measuring the earth's magnetic field.

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See also: Varian, Sigurd Fergus

SUBJECT AREA: Electronics and information technology, Telecommunications

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Sigurd Varian left school in 1920 and entered California Polytechnic to study engineering, but he soon dropped out and trained as an electrician, taking up employment with the Southern Californian Edison Company. As a result of working on an airfield he developed an interest in flying. He took lessons and in 1924 bought a First World War biplane and became a "barnstorming" pilot, giving flying displays and joy-rides, etc., to earn his living. Beset by several prolonged bouts of tuberculosis, he used his periods of recuperation to study aerial navigation and to devise navigation instruments. In 1929 he took a permanent job as a pilot for Pan American in Mexico, but in 1935 he went to California to work on electron tubes with his younger brother, Eric. They were soon joined by Russell, and with William Hansen they developed the klystron. For details of this part of his life and the founding of Varian Associates, see under Russell Varian. In later years, his health increasingly poor, he lived in semi-retirement in Mexico, where he died in a plane crash while flying himself home.

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