There is scarcely any fixed or fatty oil which has not been used, more or less, for burning. Many oils are so used in the districts which produce them, although they hardly enter into ordinary commerce under the name of burning oils. The so-called fish oils (sperm, whale, and seal) were, in recent times, principal burning oils, and to a limited extent are still so employed. Of the vegetable oils of commerce, colza oil is the most extensively used as an illuminant, and after it come other rape oils, poppy oil, the lower qualities of olive oil, sesamum or gingelly oil, candle-nut oil, and ground-nut oil, all of which, however, are local or restricted in consumption. The suitability of fixed oils for burning purposes depends on their purity or freedom from foreign matters, and on their limpidity, or, what is in effect the same thing, the temperature at which they solidify. Thus cocoa-nut fat is consumed in ordinary lamps in tropical regions, although in temperate latitudes it is a permanent solid. In the combustion of a fixed oil in lamps, the oil undergoes destructive distillation, and at the burning point is resolved into a gaseous mixture. The comparative viscosity of all fixed oils renders it necessary to adopt some device supplementary to the capillary action of the wick for maintaining at the level of the burner a supply of oil sufficient to support uniform combustion. Again, the lubricant properties of fixed oils make it practicable to adopt various mechanical devices to regulate the supply of fuel to the burner, and otherwise control illumination.

The mineral oils, on the other hand, are, as sold, mixtures of various volatile hydrocarbons which give off inflammable vapours at comparatively low temperatures, und in consumption in lamps they come to the burning point in the condition of vapour. With highly volatile oils, and the use of imperfectly fitted lamps, though not •with proper oil and fittings, there is some danger of explosion; there is also a risk that with imperfect combustion deleterious gases may be diffused through an apartment. Mineral oils possess such a high degree of limpidity that the suction of the wick alone is generally sufficient to bring the necessary supply of fuel to the burner.

The qualities of a lamp are judged of by the brilliance, steadiness, and uniformity of light it yields in proportion to the quantity of oil it consumes; by the convenient position of the light in relation to the equal illumination of the space it has to light; by the form, portability, and convenience of the lamp itself; and by the simplicity and economy of its construction, regard being had to efficiency. The chief points to consider in connexion with the structure of lamps are (1) the means of supplying oil to the burner and of regulating that supply, (2) the form and arrangement of the wick or medium over which the flame is supported, (3) the regulation and control of the currents of air in the lamp which support combustion, and (4) the position of the oil reservoir in relation to the dissemination of the light and the stability of the lamp itself.

The simple form which was used down to the end of the 18th century, and which as a “cruisie” continued in common use in Scotland till the middle of this century, illustrates the most elementary and most imperfect arrangement of a limp. Here, as in the lamps of antiquity, the oil vessel lies immediately behind the burning point of the wick, with which the oil is about level when the reservoir is full. The wick is a round soft cord or fibrous mass. Such a lamp has no merit but simplicity. The light is thrown only forward and to the sides, the back being entirely in shadow. The wick, being a round solid mass, takes up oil equally at the centre and circumference; but to the outer edges of the flame only is there any access of air; consequently combustion in the centre is imperfect, resulting in a smoky unsteady flame, and a discharge into the atmosphere of the acrid products of destructive distillation. Further, as the level of the oil sinks in the reservoir, the wick has to feed the flame from a greater distance by mere capillary force, and, the supply thus diminishing, the light decreases in proportion.

Since the time when inventors first began to better the primitive lamp, just one hundred years ago, the improvements in lamp construction have been enormous; the forms and modifications of invention bearing on lamps have been innumerable, and many excellent devices which did good service have been superseded by others simpler and more efficient. Notice can here be taken only of such inventions as developed new principles and features of originality.

The first improvement was in wicks and burners. In 1783 Leger of Paris devised a flat band or ribbon wick and burner, which produced a broad thin flame with no core, so that all parts of the oil supply were brought into intimate contact with the air, and perfect combustion and a steady flame were secured. The deficiencies of the flat wick flame were that the light was comparatively thin and impoverished, and that the parts of a room facing the thin ends of the flame were badly illuminated. To some extent these evils were overcome by the adoption of a curved form of burner, which in the end led up to the burner invented by Ami Argand of Paris, and patented in England in 1784. In its simplest form the Argand burner consists of two concentric tubes or cylinders, between which the tubular wick is contained. The inner tube is open throughout, and to it a current of air passes from below, and, being carried upwards by the draught of the flame, atmospheric oxygen for combustion is supplied as well to the inner circumference as to the outer side of the flame, whence the name “double current burner” which it frequently receives. An adequate and controllable flow of air to the interior of the Argand burner having been secured, it remained to devise some means by which the current supplied to the outer circumference of the flame could be strengthened and regulated. This Argand secured by means of a chimney, which was made at first of sheet iron and suspended over the flame; but that device was quickly abandoned in favour of a glass chimney which rested on a perforated gallery placed a little below the level of the burner. Subsequent experience suggested the formation of a shoulder or constriction on the chimney at a point a little above the level of the flame, whereby the air current is directed inward against the external surface of the flame, thus materially improving the combustion. Argand’s original burner is the parent form of innumerable modifications all more or less complex in their adaptations.

A typical example of the burner and chimney is represented in fig. 1, in which the burner is composed of three tubes, d, f, g. The tube g is soldered to the bottom of the tube d, just above o, and the interval between the outer surface of the tube g and the inner surface of the tube d is an annular cylindrical cavity closed at bottom, containing the cylindrical cotton wick immersed in oil. The wick is fixed to the wick tube ki, which is capable of being moved spirally; within the annular cavity is also the tube f, which is capable of being moved round, and serves to elevate and depress the wick. P is a cup that screws on the bottom of the tube d, and serves to receive the superfluous oil that drops down from the wick along the inner surface of the tube g. The air enters through the holes o, o, and passes up through the tube g to maintain the combustion in the interior of the circular flame. The air which maintains the combustion on the exterior part of the wick enters through the holes w, with which rn is perforated. When the air in the chimney is rarefied by the heat of the flame, the surrounding heavier air, entering the lower part of the chimney, passes upward with a rapid current, to restore the equilibrium. RG is the cylindrical glass chimney with a shoulder or constriction at R, G. The oil flows from a side reservoir, and occupies the cavity between the tubes g and d. The part ki is a short tube, which receives the circular wick, and slides spirally on the tube g, by means of a pin working in the hollow spiral groove on the exterior surface of g. The wick-tube has also a catch, which works in a perpendicular slit in the tubef; and, by turning the tube f, the wick-tube will be raised or lowered, for which purpose a ring, or gallery, rn, fits on the tube d, and receives the glass chimney RG; a wire S is attached to the tube f, and, bending over, descends along the outside of d. The part rn, that supports the glass chimney, is connected by four other wires with the ring q, which surrounds the tube d, and can be moved round. When m is turned round, it carries with it the ring q, the wire S, and the tube ∕, and thereby produces elevation or depression of the wick.

A device in the form of a small metallic disk or button, known as the Liverpool button from having been first adopted in the so-called Liverpool lamp, effects for the current of air passing up the interior of the Argand burner the same object as the constriction of the chimney RG secures in the case of the external tube. The button fixed on the end of a wire is placed right above the burner tube g, and throws out equally all round against the flame the current of air which passes up through g. The result of these expedients, when properly applied, is the production of an exceedingly solid brilliant white light, absolutely smokeless, this showing that the combustion of the oil is perfectly accomplished.

The means by which a uniformly regulated supply of oil is brought to the burner varies of course with the position of the oil reservoir. In some lamps, not now in use, by ring-formed reservoirs and other expedients, the whole of the oil was kept as nearly as possible at the level of the burner. In what are termed fountain, reading, or study lamps, the principal reservoir is above the burner level, and various means are adopted for maintaining a supply from them at the level of the burner. But the most convenient position for the oil reservoir in lamps for general use is directly under the burner, and in this case the stand of the lamp itself is utilized as the oil vessel. In the case of fixed oils it is necessary with such lamps to introduce some appliance for forcing a supply of oil to the burner, and very many methods of effecting this have been devised, most of which were ultimately superseded by the moderator lamp. The Carcel or pump lamp, invented by Carcel in 1800, is still to some extent used in France. It consisted of a double piston or pump, forcing the oil through a tube to the burner, worked by ingenious clockwork arranged to go a certain number of hours.

An example of a form of reading lamp still in general use is seen in section in fig. 2. The lamp is mounted on a standard on which it can be raised or lowered at will, and fixed by a thumb screw. The oil reservoir is in two parts, the upper ac being an inverted flask which fits into bb, from which the burner is directly fed through the tube d; h is an overflow cup for any oil that escapes at the burner, and it is pierced with air-holes for admitting the current of air to the centre tube of the Argand burner. The lamp is filled with oil by withdrawing the flask ac, filling it, and inverting it into its place. The under reservoir bb fills from it to the burner level ee, on a line with the mouth of ac. So soon as that level falls below the mouth of ac, a bubble of air gets access to the upper reservoir, and oil again fills up bb to the level ee, and so on it goes as long as combustion continues and the supply of oil in ac endures. The principle is susceptible of numerous modifications.

The moderator lamp (fig. 3), invented by Μ. Franchot about 1836, from the simplicity and efficiency of its arrangements rapidly superseded almost all other forms of mechanical lamp. The two essential features of the moderator lamp are (1) the strong spiral spring which, acting on a piston within the cylindrical reservoir of the lamp, serves to propel the oil to the burner, and (2) the ascending tube C through which the oil passes upwards to the burner. The latter consist of two sections, the lower fixed to and passing through the piston A into the oil reservoir, and the upper attached to the burner. The lower or piston section moves within the upper, which forms a sheath enclosing nearly its whole length when the spring is fully wound up. Down the centre of the upper tube passes a wire, “the moderator,” G, and it is by this wire that the supply of oil to the burner is regulated. The spring exerts its greatest force on the oil in the reservoir when it is fully wound up, and in proportion as it expands and descends its power decreases. But when the apparatus is wound. up the wire passing down the upper tube extends throughout the whole length of the lower and narrower piston tube, obstructing to a certain extent the free flow of the oil. In proportion as the spring uncoils, the length of the wire within the lower tube is decreased; the upward flow of oil is facilitated in the same ratio as the force urging it upwards is weakened. In all mechanical lamps the flow is in excess of the consuming capacity of the burner, and in the moderator the surplus oil, flowing over the wick, falls back into the reservoir above the piston, whence along with new supply oil it descends into the lower side by means of leather valves a, a. B represents the rack which, with the pinion D, winds up the spiral spring hard against E when the lamp is prepared for use. The moderator wire is seen separately in GtG; and FGÙ illustrates the arrangement of the sheathing tubes, in the upper section of which the moderator is fixed.

Lamps for Mineral Oils. — At an early period numerous attempts were made to utilize the highly inflammable volatile hydrocarbons and alcohols, which from their cheapness and abundance offered some hope of competing with the fixed oils then in universal use for illuminating purposes. These lamps had little success, and no small danger accompanied their limited use. The Vesta lamp of Young, introduced in 1834 for burning spirit of turpentine under the name of camphine, procured a smokeless flame by means of the Argand burner, constricted chimney, and Liverpool button, with the access of abundant air. It was not, however, till the introduction of paraffin oils and petroleum that mineral oil lamps became of great importance. Lamp makers had not to direct their attention to mechanical arrangements, for mineral oils rise abundantly by capillarity alone; the problem was to produce a sufficiently powerful current of air to ensure complete and smokeless combustion of these richly carbonaceous compounds, and, in view of the highly volatile nature of the liquids dealt with, to prevent their exposure to the air, and more particularly to prevent the heating of the oil reservoir which would generate explosive mixtures, or vapours of dangerous tension.

Mineral oil lamps, like those for fixed oils, are constructed with both circular or tubular and flat-wick burners. In the case of the latter a cone or brass cap is placed over the burner, having a slit or opening a little longer and wider than the wick-holder itself. This cone serves to direct the whole current of air which enters below against the surface of the flame, and mingling with the vapour of the oil produces perfect combustion, with a white flame which rises over the slit in the cone. The cool air current entering under the cone is also beneficially utilized in preventing the undue heating of the oil reservoir and the metallic wick-holder which passes down into it.

These flat wick lamps are simple in construction, cheap, and, so far as they go, economical light producers, but their flame is thin, and it is not practicable to compensate for the thinness by increased breadth of wick, because in such a case the edges of the light come so near the chimney that at these points the glass becomes rapidly heated, causing unequal expansion and destruction of the chimney. In 1865 Messrs James & Joseph Hinks of Birmingham secured a patent for improvements in the burners of mineral oil lamps, “whereby two or more flat flames or one circular or nearly circular flame may be produced by the use of two or more single flat wicks.” Under this patent was manufactured their well-known duplex lamp, which has gone far to supersede all other forms.

An improved form of their lamp is shown in fig. 4, in which a portion of the cone B is removed to show the two parallel flat wicks A, A, which have each a separate slit or opening in the cone. C is the coincident winder for raising or lowering the wicks in the tubes, by which the wicks can be moved separately or simultaneously as desired. D is a lever for raising the extinguishers E, whereby not only is the light instantly extinguished, but the wicks are also covered and protected from dirt, while all evaporation by the wick-holder is prevented. Messrs Hinks & Son have further devised an automatic lighting attachment which obviates the necessity of raising the glass chimney for lighting the lamp.

Messrs Hinks claimed in their 1865 patent the use of “two or more flat flames,” and since that period numerous burners have been produced in foreign countries in which more than two flat wicks are used. The crown burner of Brünner in Vienna contains no less than six flat wicks. There are triplex burners, too, in which the wicks are arranged as a triangle; a most valuable lamp of this construction is the “Hesperus” of Messrs Jones & Willis of Birmingham. Another form, the triplexicon, has three burners so closely placed together that the flames coalesce into a solid flame about half an inch in thickness. Further, there are star-shaped and cruciform burners, and others of little practical value.

The circular or tubular burners for mineral oils have been much simplified from the forms necessary in the case of colza, &c. A tubular wick is no longer required; a simple flat wick of a size that will allow its edges exactly to meet round the upper edge of the burner ring is used instead. In the form shown in fig. 5 the wickholder and burner consists of a hollow truncated cone, with a vertical conical section removed from its side. The flat wick passes up through this cone, its edges meeting and forming in effect a circular wick at the top, while the central current of air gets ready access to the tube by the conical opening formed in its side, and the outer current passes up within the chimney walls as usual. This form also is easily susceptible of numerous modifications. (J. PA. )

Ancient Lamps.— Though Athenaeus states (xv. 700) that the lamp (λύχνο?) was not an ancient invention in Greece, it had come into general use there for domestic purposes by the 4th century B.C., and no doubt had long before been employed for temples or other places where a permanent light was required...

Lampedusa is the Lopadussa of Strabo. In 1555 Andrew Doria anchored the vessels of Charles V. at Lampedusa, after an engagement with the Turks. Alphonso of Aragon made the island a fief of one of his courtiers, who sold it in 1677 to the prince Ferdinand Tommasi. But no permanent settlement seems to have been effected; the place, according to popular belief, was too terribly haunted by apparitions. Sir Kenelm Digby relates (1628) that his m m told him “there dwelt no persons in Lampedusa, but there is a lamp perpetually burning. The Turks have great reverence to the place, and always leave oil or bread or something behind them through devotion, but they know not for whom, and it hath proved very fatal to carry away anything from thence as well to Christians as to Turks.” Dumont, who personally visited the island, mentions a “little chapel dedicated to the Virgin, in which there is an altar with a turban laid upon it, which is usually called Mohammed’s tomb,” and adds the popular belief that any one attempting to carry off the gifts would be miraculously prevented escaping the island. The earl of Sandwich (1737) found Lampedusa with but a solitary inhabitant; and Captain Smyth states that about 1815 it was leased by an Englishman, Fernandez, who lived alone with his family. Ferdinand II. of Bourbon claimed it as Government property, and from 1843 attempts were made to establish a regular colony at the national expense. About £17,000 per annum was expended on the project, but the result was far from satisfactory. The population, introduced from Sicily, remained stationary during twenty years. Catherine II. at one time proposed to purchase Lampedusa for the purpose of making it a Russian naval station.

If it could be shown that Shakespeare derived the material of The Tempest from an Italian original, Lampedusa would have very strong claims to be considered the first prototype of the enchanted isle. It is the Lipadosa of Orlando Furioso, the scene of the shipwreck of Roger of Sicily and of his conversion by the hermit. A Sicilian legend which forms the subject of Wieland’s poem Klelia und Sinibald, oder die Bevölkerung von Lamped use, tells how two ladies of Palermo were cast ashore on the island, and found there two hermits who fell so deeply in love with them as to renounce their ascetic life. In Sicilian the “hermit of Lampedusa” corresponds to the English Vicar of Bray, lighting up the chapel near his cell with equal readiness for the Crescent or the Cross.

See Crusiιιs, Turco-Graecia, Ba-el, 1584; Digby, Journal of a Voyage into the Mediterranean, Camden Society, 1868: Dumont, 'Nouvelle Voyage au ierant, The Hague, 1694, London, 1702; Captain Smyth, Memoir Descriptive of the Resources of Sicily, 1824; Joseph Hunter, New Illustrations of Shakspeare, vol. i., 1845.