A vessel in which fluid combustibles are burned for the purpose of affording artificial light. This is effected by means of a wick or burner (commonly composed of a few threads of linen or cotton), which is immersed in the fluid, and its upper extremity lighted; the fluid then rising gradually by capillary attraction to the lighted end becomes decomposed, and its constituent parts form various gaseous compounds, most of which are inflammable, and these take fire and burn with a degree of brilliancy varying with the nature of the fluid from which they are obtained. The wick being now surrounded by the flame of the burning gases is maintained at a heat sufficient to decompose fresh portions of the combustible matter as they continue to rise to it. The office of the wick, therefore, is merely to decompose the oil or other fluid, and not to afford light by the burning of its own substance; for although the wick or burner is generally composed of some combustible material, yet provided that it be kept plentifully supplied with oil it is consumed so slowly as to afford no perceptible increase of light; and frequently wicks composed of incombustible substances are employed, as asbestos, metallic wire, glass, etc.; and some years back Messrs. S. and D. Gordon obtained a patent for lamps with incombustible wicks, formed of the above-named substances, by drawing the material into fine threads, which are afterwards formed into small bundles and bound round spirally with wire, or rolled up in a piece of fine wire gauze, forming a cylindrical bandage or covering to each bundle.
The wicks thus formed contain a vast number of minute interstices, arranged longitudinally in parallel lines, and being placed in an inflammable volatile liquid (as naphtha or alcohol), the liquid is conveyed by capillary attraction to the upper part of the wick for ignition. The composition to be burned in these lamps constitutes another branch of the improvements mentioned in the patent, and consists of a mixture of one part of essential oil with, five or six of alcohol or naphtha (which latter is much more economical.) By this admixture a much more brilliant light is obtained than when alcohol alone is used, whilst the smoke and deposit of carbonaceous matter upon the wick which attends the combustion of essential oils by themselves is avoided. These lamps have been made up into a great variety of elegant designs, both modern and antique; they have also been fitted into frames and stands to be placed under tea-urns, coffee-biggins, and tea-kettles, and are extremely convenient in numerous situations, whilst the expense is inconsiderable. They have a circular ring at top for receiving the kettle or other culinary vessel, with the lamp in the centre, lying in a frame, which may be taken out at pleasure as a distinct apparatus to afford light instead of heat.
The wicks being incombustible, no snuffing or attention to them is requisite during the time of ignition; all that is necessary is to keep them free from dust when not in use, by screwing on a cap over each wick tube, and to put the plug in the central air-hole to prevent evaporation.
Mr. Blackadder, of Edinburgh, has also paid attention to the subject of lamps with incombustible wicks, and has given in the Edinburgh Philosophical Journal a description of several lamps of this description which he had contrived, some of which were well adapted for the combustion of essential oils, spirits of turpentine, etc. The burners he employed consisted of short pieces of bugle heads; some of these he inserted in pieces of talc, and found them to form a very convenient floating light when placed upon the surface of a portion of oil in a glass vessel. Mr. Blackadder's account of these lamps having called the attention of manufacturers to the subject, gave rise to the floating lights now in such general use as night lights, consisting of a short piece of capillary glass tube of very small diameter inserted in the bottom of a thin metallic dish or cup, and placed in a glass vessel containing oil. The cut in the following page represents an improved lamp of this description, which has this peculiar advantage over the ordinary ones, that it is capable of yielding four distinct degrees of flame, so that it may be accommodated to the occasion; a larger or a smaller one being used according as convenient This effect is produced by means of two small weights in the form of rings, fitted to lie in a recess at the bottom of the floating dish; by the addition or removal of these weights the immersion of the dish is regulated so as to cause a greater or less flow of oil through the tube, and consequently to produce a larger or smaller flame; when both weights are removed, the lowest degree of flame, marked 1 in the drawing, is produced;with the smallest ring the flame 2 will be obtained; with the largest, the flame 3; and with the two rings together, the flame will be equal to that marked 4.
We extract from the Edinburgh Philosophical Journal, the following description of a "self-generating gas lamp," a title which is equally applicable to every other kind of lamp, since all generate the gas from which the light is obtained; the difference is, that in this lamp the oil is decomposed and converted into gas by falling on a substance previously heated, and the gas is ignited as it issues from the orifice of a tube situated beneath the decomposing chamber, the heat of which is maintained by the flame of the gas; whereas, in the ordinary lamps, the oil is decomposed and ignited at the same point, viz. at the wick. "The oil vessel of this lamp is represented at A., B is the tube by which the oil is admitted; C is the generator; D is a hollow vessel, where the heat from the burners F, underneath, is collected; the dotted lines are projecting ridges on it within the generator, to prevent the oil running down and collecting at the bottom of the generator. E is a circular piece of iron to collect and retain the heat; G are tubes to conduct the gas from C to F; L is a tube to supply the vacancy in it with gas, as the oil is discharged into C; H is a metal heater to fit into D. To use the lamp, fill A par-cially with oil, alcohol, or any fluid from which gas is produced, and having made the metal heater H red hot, place it in the bulb D; after it has continued in it a minute or two, turn the stop-cock I, allowing the fluid to drop slowly on the heated bulb D below, by which it will be converted into gas.