Читать книгу Artificial Light: Its Influence upon Civilization - Matthew Luckiesh - Страница 16

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It will be noted that the light-sources throughout the early ages were flames, the result of burning material. This principle of light-production has persisted until the present time, but in the latter part of the nineteenth century certain departures revolutionized artificial lighting. However, it is not the intention to enter the modern period in this chapter except in following the progress of the oil-lamp through its period of scientific development. The oil-lamp and the candle were the mainstays of artificial lighting throughout many centuries. The fats and waxes which these light-sources burned were many but in the later centuries they were chiefly tallow, sperm-oil, spermaceti, lard-oil, olive-oil, colza-oil, bees-wax and vegetable waxes. Those fuels which are not liquid are melted to liquid form by the heat of the flame before they are actually consumed. The candle is of the latter type and despite its present lowly place and its primitive character, it is really an ingenious device. Its fuel remains conveniently solid so that it is readily shipped and stored; there is nothing to spill or to break beyond easy repair; but when it is lighted the heat of its flame melts the solid fuel and thus it becomes an "oil-lamp." Animal and vegetable oils were mainly used until the middle of the nineteenth century, when petroleum was produced in sufficient quantities to introduce mineral oils. This marked the beginning of an era of developments in oil-lamps, but these were generally the natural offspring of early developments by Ami Argand.

Before man discovered that nature had stored a tremendous supply of mineral oil in the earth he was obliged to hunt broadcast for fats and waxes to supply him with artificial light. He also was obliged to endure unpleasant odors from the crude fuels and in early experiments with fats and waxes the odor was carefully noted as an important factor. Tallow was a by-product of the kitchen or of the butcher. Stearine, a constituent of tallow, is a compound of glyceryl and stearic acid. It is obtained by breaking up chemically the glycerides of animal fats and separating the fatty acids from glycerin. Fats are glycerides; that is, combinations of oleic, palmetic, and stearic acids. Inasmuch as the former is liquid at ordinary temperatures and the others are solid, it follows that the consistency or solidity of fats depend upon the relative proportions of the three constituents. The sperm-whale, which lives in the warmer parts of all the oceans, has been hunted relentlessly for fuels for artificial lighting. In its head cavities sperm-oil in liquid form is found with the white waxy substance known as spermaceti. Colza-oil is yielded by rape-seed and olive-oil is extracted from ripe olives. The waxes are combinations of allied acids with bases somewhat related to glycerin but of complex composition. Fats and waxes are more or less related, but to distinguish them carefully would lead far afield into the complexities of organic chemistry. All these animal and vegetable products which were used as fuels for light-sources are rich in carbon, which accounts for the light-value of their flames. The brightness of such a flame is due to incandescent carbon particles, but this phase of light-production is discussed in another chapter. These oils, fats, and waxes are composed by weight of about 75 to 80 per cent. carbon; 10 to 15 per cent. hydrogen; and 5 to 10 per cent. oxygen.

Until the middle of the eighteenth century the oil-lamps were shallow vessels filled with animal or vegetable oil and from these reservoirs short wicks projected. The flame was feeble and smoky and the odors were sometimes very repugnant. Viewing such light-sources from the present age in which light is plentiful, convenient, and free from the great disadvantages of these early oil-lamps, it is difficult to imagine the possibility of the present civilization emerging from that period without being accompanied by progress in light-production. The improvements made in the eighteenth century paved the way for greater progress in the following century. This is the case throughout the ages, but there are special reasons for the tremendous impetus which light-production has experienced in the past half-century. These are the acquirement of scientific knowledge from systematic research and the application of this knowledge by organized development.

The first and most notable improvement in the oil-lamp was made by Argand in 1784. Our nation was just organizing after its successful struggle for independence at the time when the production of light as a science was born. Argand produced the tubular wick and contributed the greatest improvement by being the first to perform the apparently simple act of placing a glass chimney upon the lamp. His burner consisted of two concentric metal tubes between which the wick was located. The inner tube was open, so that air could reach the inner surface of the wick as well as the outer surface. The lamp chimney not only protected the flame from drafts but also improved combustion by increasing the supply of air. It rested upon a perforated flange below the burner. If the glass chimney of a modern kerosene lamp be lifted, it will be noted that the flame flickers and smokes and that it becomes steady and smokeless when the chimney is replaced. The advantages of such a chimney are obvious now, but Argand for his achievements is entitled to a place among the great men who have borne the torch of civilization. He took the first step toward adequate artificial light and opened a new era in lighting.

The various improvements of the oil-lamp achieved by Argand combined to effect complete combustion, with the result that a steady, smokeless lamp of considerable luminous intensity was for the first time available. Many developments followed, among which was a combination of reservoir and gravity feed which maintained the oil at a constant level. In later lamps, upon the adoption of mineral oil, this was found unnecessary, perhaps owing to the construction of the wick and to the physical characteristics of the oil which favored capillary action in the wick. However, the height of the oil in the reservoir of modern oil-lamps makes some difference in the amount of light emitted.

The Carcel lamp, which appeared in 1800, consisted of a double piston operated by clockwork. This forced the oil through a tube to the burner. Franchot invented the moderator lamp in 1836, which, because of its simplicity and efficiency soon superseded many other lamps designed for burning animal and vegetable oils. The chief feature of the moderator lamp is a spiral spring which forces the oil upward through a vertical tube to the burner. These are still used to some extent in France, but owing to the fact that "mechanical" lamps eventually were very generally replaced by more simple ones, it does not appear necessary to describe these complex mechanisms in detail.

When coal is distilled at moderate temperatures, volatile liquids are obtained. These hydrocarbons, being inflammable, naturally attracted attention when first known, and in 1781 their use as fuel for lamps was suggested. However, it was not until 1820 that the light oils obtained by distilling coal-tar, a by-product of the coal-gas industry which was then in its early stage of development, were burned to some extent in the Holliday lamp. In this lamp the oil is contained in a reservoir from the bottom of which a fine metal tube carries the oil down to a rose-burner. The oil is heated by the flame and the vaporized mineral oil which escapes through small orifices is burned. This type of lamp has undergone many physical changes, but its principle survives to the present time in the gasolene and kerosene burners hanging on a pole by the side of the street-peddler's stand.

Although petroleum products were not used to any appreciable extent for illuminating-purposes until after the middle of the nineteenth century, mineral oil is mentioned by Herodotus and other early writers. In 1847 petroleum was discovered in a coal-mine in England, but the supply failed in a short time. However, the discoverer, James Young, had found that this oil was valuable as a lubricant and upon the failure of this source he began experiments in distilling oil from shale found in coal deposits. These were destined to form the corner-stone of the oil industry in Scotland. In 1850 he began producing petroleum in this manner, but it was not seriously considered for illuminating-purposes. However, in Germany about this time lamps were developed for burning the lighter distillates and these were introduced into several countries. But the price of these lighter oils was so great that little progress was made until, in 1859, Col. E. L. Drake discovered oil in Pennsylvania. By studying the geological formations and concluding that oil should be obtained by boring, Drake gave to the world a means of obtaining petroleum, and in quantities which were destined to reduce the price of mineral oil to a level undreamed of theretofore. To his imagination, which saw vast reservoirs of oil in the depths of the earth, the world owes a great debt. Lamps were imported from Germany to all parts of the civilized world and the kerosene lamp became the prevailing light-source. Hundreds of American patents were allowed for oil-lamps and their improvements in the next decade.