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A Short History of Electric Light

by Frank Andrews

The Arc Lamp

The very first form of practical lighting produced by electricity was virtually an open flame. It bore little relationship to the lightbulb except for sharing a common purpose and source of energy. The arc lamp operates by positioning two pointed carbon rods opposite one another, each connected to a different pole of the power supply. The tips are then brought into contact so that the electricity flows through them causing the tips to heat up slightly. They are then pulled apart very slowly and a spark, or arc, of electricity leaps the gap, causing the temperature of the tips to rise further. When the tips are hot enough, vaporising carbon becomes incandescent giving an intense blue white light. It requires about fifty volts to create this arc and the tip temperature rises to about 4,000° Centigrade. The original arc lamps were powered from batteries given a continuous DC current, most of the light was generated on the tip of the positive rods. As the carbon was consumed by the arc a hollow formed on the positive tip and the negative tip remained pointed. The positive rod was used up at about twice the rate of the negative. If the light source was to remain central the adjustment of the rods had to allow for the different rates of consumption. When observing a DC arc lamp, using dark UV filter glasses to protect the eyes from intense light high in Ultra Violet radiation, it can be seen that the source of the light is within the hollow of the positive tip. One would observe too that the actual arc although visible gives off very little light itself. When an alternating current AC supply is used the burn tends to be little irregular. The light output for a given voltage would be less with AC than with DC. On AC arcs both tips give a similar intensity and will be consumed at an equal rate because the polarity of the tips is changing many times per second. With both types, if the rods are not kept at a constant distance, the arc will grow and the temperature fall giving less light until it can no longer cross the gap and stops completely. After the discovery of the arc lamp most of the development was in the methods of maintaining the gap automatically and in the formulation of the rods themselves. It was not a cheap method of lighting and the intense brightness was not a practical proposition for domestic use. Later arc lamps were given a removable glass jacket. The arc is cleaner and brighter if it burns in a fairly well sealed glass envelope to reduce the amount of oxygen. The glass enclosure also protects the arc from draughts which could affect the arc. Some of the lamps made in the 1930’s to 1960’s had the external appearance of ordinary, but large, light bulbs.

Sir Humphrey Davy, used wood charcoal for his demonstration of the Arc Lamp at the Royal Society, The Royal Society in 1808. He connected two thousand cells for the demonstration which must have been very impressive. They impressed Michael Faraday who had been attending Davy’s lectures in his spare time and was later to become very important in the development of lighting.

Jean Bernard Léon Foucault was born in 1819 in France. He introduced Plumbago, gas-carbon, rods which were of a more consistent quality and would burn at a slower rate. He also invented some important mechanisms for automatically feeding the rods towards each other. These were clockwork driven and controlled by an electro-magnet operated by the current across the arc. Later even denser artificial coke carbons were developed for reliability and longevity. He died in 1868. There were very many variations on Foucault’s drive mechanism. In France by Duboscq Soleil, Serrin, Joseph Deleuil and in England by Staite, Slater & Watson and by M. J. Roberts.

An English engineer William Edward Staite, born 1809, produced a weight driven mechanism in 1846. It was controlled by the heat of the arc expanding and contracting a copper strip. While technically better than Foucaults it made little progress due to the renowned short-sightedness of the English business community. Edison & Swan both used versions of Staite’s lamp with improvements by W. Petrie in the 1870’s. Staite died in 1854.

Paul Jablochoff was born in Russia in 1847. He was a telegraph engineer in the Russian Army and in 1876 he developed the ‘Electric Candle’, in which two thin carbon rods were fixed parallel with a separating layer of Plaster of Paris. To light the lamp there was a thin strip of carbon across the top that quickly burnt away and started the arc after connecting the power. The arc would vaporise the plaster as it burnt down and the only mechanical task necessary was replacing the rod assembly. As the rods had to burn at the same rate this system had to use alternating current and at the time when most power was from batteries this was thought to be inconvenient. French businessmen saw its potential and set up a company Compagnie Générale d’Électriqué (CGE) to manufacture and market it. Its first major installation was at the Grand Magasins de Louvre, Paris, where 80 were used. They were also used for the experimental installations on the Thames Embankment and Holborn Viaduct in London. By 1881 there were more than 4,000 in use although the differential arc lamp was beginning to replace it by then. Jablochoff died in 1894.

In Germany Friederich von Hefner‑Alteneck of Siemens & Halske developed a 1,000 cp (candlepower) self regulating differential arc in 1878. This began Siemens & Halske’s involvement in the electric lighting business. Colonel R. E. B. Crompton also developed a differential arc the following year in the UK.

Joseph Deleuil gave a demonstration of the arc lamp in the Place de la Concorde, Paris, in 1844. The first installation of arc lamps was at the mill of Heilmann, Ducommun and Steinlein at Mülhausen in France during August 1875. This was followed by platform lighting at La Chapelle station by the railway company Compagnie de Nord. In England the first electric street lighting was on the Thames Embankment, London in 1878 using Jablochoff Candles. Godalming, Surrey was the first site for municipal street lighting using Arc lamps and the worlds first public generating station in 1881. The first major installation in Germany was for street lamps on the Potsdamer Platz in Berlin. In the U.S.A. Charles Francis Brush installed his arc lamps and dynamo at Wannamakers Philadelphia department store in 1879.

Colonel R. E. B. Crompton was born in 1845. He developed steam engines during his army commission in India and on leaving the army continued his engineering career. He installed a Gramme dynamo and arc lamps at his brother’s iron foundry, in Nottinghamshire, to improve efficiency for nightworking. Following this success he was commissioned to install a similar system at Whiteley’s department store in Queensway, London. In 1878 he set up Crompton & Company to manufacture arc lamps and the Burgin dynamo with A. P. Lundberg. Crompton & Company lit the St. Enoch’s railway station in Glasgow, Scotland, the Alexandra Palace and the Law Courts in London. In 1879 he developed a small version of the Gramme dynamo for mounting on steam tractor engines and used one of these to supply power for arc lamps at his home in London. He was actively involved in the early marketing of Swan’s incandescent lamps and later manufactured them under licence. In 1886 he formed the Kensington & Knightsbridge Electric Supply Company providing the first house to house to house electrical supply and was a staunch advocate of direct current supplies. He died in 1940.

Sebastian Ziani Ferranti was born in 1864. He started work with Siemens at their English works from 1881 to July 1882. He left to develop his zig-zag armature for a revolutionary design of alternator. In September 1882 he set up his own company, Ferranti Thompson and Ince Limited, in Appold Street, London, where he manufactured the alternator and arc lamps. In 1883 he merged with the Hammond Company to form the Ferranti Hammond Electric Light Company in Bermondsey Street, London. After this business failed he set up another company in Hatton Garden to manufacture his alternator and a mercury supply meter he had developed. Within a year he took over the Grosvenor Gallery lighting installation. In 1887 the London Electricity Supply Corporation Ltd was set up to exploit his innovative ideas on electricity supply that laid the foundation for the modern system. A power station was built at Deptford with sufficient output to provide all the lighting needs of London at that time but government legislation localising power supply prevented its full use.

Most of the early installations in Europe and the UK were carried out by French companies. French businessmen had been more longsighted than the English who were suspicious of electricity. The Compagnie de l’Alliance and Sulzer brothers were the largest operations. Sulzer Brothers installed arc lighting at the Royal Opera House in London and the Burg theatre in Vienna.

Charles Francis Brush born in the USA in 1849 designed and marketed a dynamo and arc lamp in 1876. A drawback of the Foucault gap regulating system was that if more than one lamp was connected in series the current of each would affect the others and the strongest carbon would cause the weakest to be burnt at a different rate. While only single battery powered arcs were used this was not a problem but with the advent of cheap mains power it became desirable to connect several lamps in series. To overcome this problem Brush developed a new regulator system in 1879. This used solenoids, electro-magnetic devices that give a push or pull in one direction, to maintain the gap. One would be driven by the current passing through the arcs and was used to pull the rods apart. The other was driven by a current that is proportional to the voltage difference across the arcs pushing them together. When the arcs were at the correct distance the effect of these two solenoids was equal and the illumination remained constant. This arrangement also caused the rods to come together when power was first connected to the circuit thus making the operation of the arc lamp fully automatic until the rods were consumed. Eventually a magazine was devised that automatically replaced the rods as they got used up. He formed the Brush Electric Company which became one of the largest generator manufacturers. He died in 1929.

Pure carbon rods tended, especially with alternating current, to burn erratically because of the arc wandering to the softest spots of the rods. Rods were developed that had a soft core surrounded by a hard casing, ensuring that the arc stayed central and the illuminating crater formed with regular edges.

A later variation on this principle was the Flame Arc Lamp developed by Hugo Bremmer in 1889. In these the arc itself is the main source of illumination. These were made by impregnating the carbon rods with highly volatile metallic salts which become incandescent as they burnt in the arc. The lower resistance of such rods allowed them to be made longer. The arc was more inclined to wander so they had to be cored and as thin as possible. Because they were thinner they burnt faster, to reduce the rate of burning soft metal cores were then added. The rods were arranged in a ‘V’ formation with the arc at the bottom. By adding an electromagnet above the gap the length of the arc itself could be increased. Feed was by the dual solenoid system and street lights using this type were invariably fitted with a magazine.

In 1890 there were over 130,000 arc lamps in use nightly in the United States. On the 20th October 1884 at Hallets Point, Aston, New York State, nine 250ft high towers were installed to illuminate the busy channel on the East River known as Hells Gate. Each light produced 3,000 candlepower and as a side effect illuminated the whole of Aston. Normal street arc lamps produced around 700 candlepower. They were removed in 1888 as their benefits to navigation were not as great as had been hoped for. There were no mechanical failures during their lifespan a superb illustration of the reliability of the feed mechanisms used.

Arc lamps have been in use until recent times, being replaced as a source of intense light by the short-arc xenon lamp in 1951 and by quartz‑iodine lamps in the 1960’s. Being a source of Ultra Violet light, arc lamps were also used as Sun Tan lamps.

Next Chapter - The Incandescent Lamp, 1800-1900

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