Lighting and Artificial Illumination

About 1855 R. W. von Bunsen invented a burner which bears his name. Eleven years later Dr. Carl Auer von Welsbach dis covered the gas mantle which today is used in nearly its original form. Welsbach made gas mantles by saturating cotton fabrics in a solution of certain salts and burning out the organic matter. His first mantle was made with erbium salts and gave a marked green light. He patented the mantle and the next year patented the use of thoria which added strength to the mantle. The incandescent gas mantle composed of thoria and ,ceria was announced in 1890. Thereafter, as soon as the collodion coating process was perfected, mantle lighting became practical. Many modifications and improvements have been made within the past 25 years. Acetylene generated from calcium carbide was first shown to be a possibility by Thomas M. Willson in 1892. The Pintsch system of gas lighting, invented by Richard Pintsch, a German, was brought to America in 1880. It uses distillation of oil.

Electric Lamp.

In 1752 Benjamin Franklin, experimenting with the Leyden jar, discovered the secret of lightning—nature's electricity. Fifty years later Sir Humphry Davy demonstrated the practicability of Volta's theory of obtaining electricity from cells consisting of unlike metals immersed in an acid solution. The earliest attempt at making an incandescent lamp was made by De la Rue in I82o. In 1840, Grove demonstrated his battery by lighting an auditorium with incandescent electric light. Foucault produced such a steady and continuous light that he was able to use it for photographic purposes. The first arc lamp patented in England was the Wright arc of 1845. These lamps were used for street lighting in Baltimore in the late '7os. The first patent on an incandescent lamp was granted by the British Government in 1841 to Frederick De Moleyns. J. W. Starr patented in 1845 the so-called Starr-King lamp, a "filament" formed of a stick of retort carbon. When new, the lamp gave a good, bright light, but blackened rather quickly. During the next few years, several in ventors, among whom were W. E. Staite, Edward C. Shepard, M. J. Roberts, De Changy and Moses G. Farmer, tried to make incandescent lamps, even though it was known that their use with current obtained from batteries would be impractical. The dynamo was not sufficiently improved for commercial purposes.

Sir Joseph W. Swan, who became one of the foremost incan descent lamp manufacturers in England, made from 1848--6o a number of experimental lamps. In 1865 Herman Sprengel in vented the mercury vacuum pump. In 1873 Crookes (afterwards Sir William Crookes) exhibited his radiometer and the improved means he employed, with the use of the Sprengel pump, for ob taining the near approach to a perfect vacuum which the con struction of the radiometer demanded. This led Sir Joseph Swan

to resume his incandescent lamp experiments. In 1877, with the assistance of Charles H. Stearn, he experimented with carbon conductors of various forms and sizes. These were mounted in glass bulbs which were exhausted to the highest possible degree by means of the Sprengel pump. These lamps rapidly deteriorated owing to the evolution of gases from the carbon. This difficulty was overcome by heating the outside of the bulb still connected to the exhaust pump while passing a strong current through the carbon. Straight carbon wires were found to buckle, but arch shaped carbon wires gave good results. In 1880 Swan invented the parchmentized thread which, when carbonized, produced a long, thin carbon, used for many years, made from cotton thread treated with sulphuric acid and dried, becoming agglutinated, los ing its fibrous condition and having the appearance and the hard ness of catgut.

In 1872 Lodyguine, a Russian scientist, made a lamp having a "V" shaped piece of graphite for a burner operating in nitrogen. In 1875, Kosloff, another Russian, made a lamp consisting of several graphite rods operating also in nitrogen. The rods were so arranged that only one operated at a time and, when it burned out, another was automatically connected in circuit. Konn, also a Russian, invented a lamp in 1875, similar to that of Kosloff, except that the graphite rods operated in vacuum. In 1876 Bouliguine, another Russian, made a lamp having a long graphite rod, only the upper part of which was in circuit. When this part burned out, a counterweight pushed the rod upward, placing a fresh portion of the long rod in circuit. It operated in vacuum. With the appearance of the Gramme dynamo (1875) and the use of the Sprengel vacuum pump, rapid progress was made. In 1876 Jablochkoff put his famous "candle" on the market. This simple arc lamp consisted of two carbon rods held together side by side and insulated from each other by kaolin. The kaolin vaporized as the carbons were consumed, giving the arc a peculiar colour. A complete system was developed by Jablochkoff, with an alternating-current generator used to offset the unequal con sumption of the carbons on direct current. A series system of distribution was used, and in order to prevent interruption, several candles were put in each fixture with an automatic device to con nect a fresh candle whenever one burned out. The Jablochkoff candle had a life of from about an hour and a half to three and a half hours. Thousands of candles were sold.