LAMP

(Yunanca köken — orijinale bakınız.) The general term for the well-known contrivances used in producing artificial light from the combustion of liauid or other inflammable bodies. The peculiar applicability of oil to the production of artificial light, which could not fail to be discovered at a very early period, rendered the use of lamps universal among the nations of antiquity. The Egyi)tians, the Hebrews, Greeks, and Romans, vied with each other in the construction of those instruments; and the specimens of some that have been transmitted to our times display much taste and elegance of external design. It would seem, however, that the ancients had confined 634 LAMP. themselves merely to the external embellishment of the lamp; for it is a singular circumstance, that notwithstanding the simplicity of the invention, and its obvious capability of improvement, it is only within the last sixty years that any material improvement has been effected m its original construction. To give any thing like a complete view of the principles and structure of the numerous lamps of which the present age has witne ed the invention would be quite impracticable without a multiplicity of illustrative diagrams, which would be foreign to the purpose of this work; but a brief notice of the principle on which the action of every lamp, both simple and complicated, depends, and of some of the most celebrated improvements in their structure, may not be considered out of place. The most simple lamp consists in a ve el of any shape filled with oil or other inflammable liquid, and having a short depre ion or spout on one side, in which lies a wick composed of any fibrous substance, and capable of imbibing the oil by its capillary attraction. The oil thus raised and diff'used through the wick, when ignited, admits of being heated to such a degree of temperature as is capable of volatilizing the oil, the vapour of which, in a state of combustion, constitutes the flame of the lamp. The wick of a lamp serves only for the purpose of raising up the oil by capillary attraction, and thus giving a constant and adequate supply to the flame. It furnishes no part of the light by the combustion of its own substance; for the quantity consumed is too small to merit attention, and it is usually coated over with a broad deposit of carbonaceous matter, which cannot burn for want of the acce of air, from which it is kept by the flame. To render the air acce ible to every part of the flame in order to ensure the most perfect combustion of the oil, is one of the most e ential objects in the modern improvement of lamps; and hence the texture, materials, and dimensions of" the wick are matters of much importance. If, on the one hand, the wick be large, a great deal of carbon vapour remains unburnt in the interior of the flame, and breaks out in the form of smoke, producing a most disagreeable smell; and if, on the other hand, the wick be too small, though the unconsumed carbon will naturally be le , and the flame consequently clearer than those of the larger wick, it will yield but very little light, as the light diminishes with the superficies of the flame. The inconvenience of a thick wick had been long observed, and attempts were often made to remove it; in some instances by substituting two or more small wicks for one large one, and in others by making the wick flat instead of cylindrical. These experiments, though limited in their operation, were no doubt beneficial; and in houses where economy more than elegance was studied, they procured for the lamp a more extended use than it previously enjoyed. Still, however, the smoke and disagreeable smell arising from the burning of oil in common lamps, and the unsightly appearance of the whole proce , had long banished the lamp from the apartments of the wealthy; and it was not till the year 1780, when M. Argand invented the well-known lamp which bears his name, that the instrument came into general use. This invention embraces so many improvements upon the common lamp, and has become so general throughout Europe, that it may be justly regarded as one of the greatest discoveries of the age. As a substitute even for the best wax candles, it combines the advantage of economy and convenience, with much greater brilliance; while even as a means of producing heat it is found to be of most e ential service in chemical operations. The great principle on which the superiority of this lamp depends is the admi ion of a quantity of air into the centre of the flame. This Argand accomplished by making the wick of a circular form, instead of a solid cylinder as before; by which means a current of air rushes through the hollow cylinder while the wick is burning, thus admitting air into the centre of the flame. Improving upon this invention, which was found perfectly to succeed, he added a gla cylinder or chimney, open at bottom, to surround the flame at a short distance; by which another current of air is made to pa upwards on the exterior part of the flame, and between it and the gla . Thus every part of the thin circular flame is between two currents of air, which supply the combustion with such a quantity of oxygen as to create a heat sufficient to convert into a brilliant flame the smoke which escapes from an ordinary lamp. Such is a brief accotmt of the leading principles of Argand's invention. Various improvements have since been made on the original by the Sinumbra, the French, the Iris lamp (now in general use as a table lamp), and a variety of others, which it would be superfluous to enumerate; all of which, however, may be regarded as improvements more of detail than principle. Indeed, the great merit of Argand's invention consists in the facility with which it can be ingrafted on lamps of every variety of form and structure; while not all the beauty of design and execution witne ed in the endle diversity of the lamps at present in general use, would be sufficient [s. 647]