LAMPS were first invented by the Egyptians, from whom they passed to Greece and Rome. They were made of baked earth, iron, copper, silver, gold, and glass.
Ordinary lamps are only arrangements whereby materials which are fluid at common temperatures, as the oils, are consumed. The first object is to isolate as much of the oil as is required for the production of a flame. The simplest manner in which this can be effected, is that practised in the night-lights.
On a layer of oil covering the surface of the water there swims a brass cup, at the bottom of which is a small piece of glass tube, fitted tight by a cork. Al-: though, before ignition, the oil rises in the interior of that tube above the level on the outside, yet, as the capillarity of the tube is annihilated by the heat, the fluid is actually depressed. To ob viate this, the tube must be fixed so far below the surface of the oil, that the greater pressure of the oil without shall overcome the depression within. In this manner the insulated oil in the other end may be ignited, and continues to burn by itself. The eohditions under which the oil is consumed, so far as the production of light is concerned, are most unfavora ble, although the- purpose of a night lamp is fully answered ; for the flame is much too small for producing light for common purposes ; and, if the size of the tube is increased, the oil will no longer burn, and the flame is too low down to lighten well the room. Both of these evils, particularly the latter, are avoided by the use of wicks. The common kit chen lamp is a slight improvement on this. The following are the essential points, which it has been the object of inventors to attain, sometimes singly, sometimes several at once.
1. To select such a form (section) of wick, that the quantity of decomposed oil, and the simultaneous supply of air, may stand in the relation to each other that the hydrogen and carbon may be consecutively consumed, and consequent ly no smoke produced.
2. To make the distance between the burning part of the wick and the surface of the oil as unchangeable as possible, in order that as much oil may be drawn up at last as at first.
3. To place the reservoir of oil in such a position that the shadow shall occasion little or no inconvenience. The use made of the lamp will regulate its form. Occa sionally these cannot correspond.
Thus, the shadow of waif-lamps is un important, as the lamp covers its shadow ; so the shadow of a study-lamp is not a fault, as it is only used by one person ; yet still its prevention is an improve ment.
4. To throw the light, radiating from the flame, by means of collectors and re flectors, from those parts where it is of little or no service, in the direction most required.
The requisites stated, under No. 1, have have been complied with in two ways ; first, by controlling the access of air (the quantity of air) ; on the other by regu lating the supply, and often by both at the same time. We have reference to that part of the lamp called the burner.
When there is much oil burned at the one point, the current of air supplied on the outside is never sufficient for burning away the oil completely, so as to produce only water and carbonic acid ; on the contrary, an amount of carbon is deposit ed, owing to their not being oxygen enough to burn it fully away into carbo nic acid : the flame soots. This great
evil was to a certain extent remedied by the invention of the Argand lamp, called after Mr. Argand, who first produced it in 1784. The principle on which the su periority of the Argand lamp depends, is the admission of a larger quantity of air to the flame than can be done in the com mon way.
This is accomplished by making the wick of a circular form, by which means the current of air rushes through the cyl inder on which it is placed, with great force, and along with that which has ac cess to the outside, excites the flame to such a degree that the smoke is entirely consumed. : thus both the light and heat are prodigiously increased. The combus tion being exceedingly augmented by the quantity of air admitted to the flame, and what in common lamps is dissipated in smoke is here converted into' brilliant flame. This lamp is now very much in use, and is applied not only to ordinary purposes of illumination, but also to that of a furnace for chemical operations, in which it is found to excel every other con trivance yet invented. It consists of two parts, a reservoir for the oil, and the lamp itself. The argand burner is made by forming a hollow cylindrical cavity, which receives the oil from the main body of the lamp, and at the same time transmits air through its axis or central hollow ; in this cavity is placed a circular wick attached at bottom to a movable ring ; this ring may be raised or depressed by rack and pinion work, or more comme:ly a screw, so that the height of the wick may be va ried to regulate the size of the flame. On the outside is placed a glass chimney, which transmits a current of air on the same principles as a common smoke flue. When this lamp is lighted, the combus tion is vivid and the light intense, owing to the free and rapid supply of air. The flame does not waver, and the smoke is wholly consumed. The brilliancy is in creased if the air be made to impinge later ally against the flame. This is done by nar rowing the glass chimney near the blaze, so as to bend the air inward, or by plac ing a metallic button over the blaze, so as to spread the internal current outward. To avoid the shade occasioned in com mon lamps by the reservoirs for the oil being under the flame, various contriv ances have been introduced, in which the reservoir is placed at a distance from the flame. bathe astral and ginambra lamps, the principal of which was invented by Count Rumford, the oil is contained in a horizontal ring, having a burner at the centre, communicating with the ring by two or more tubes placed like rays. The wick is placed a little below the level of the flame, and from its large surface af fords a supply of oil for many hours. A small aperture is left for the admission or escape of the air in the upper part of the ring. When these lamps overflow, it is because the ring is not kept perfectly hor izontal, or else because the air hole is ob structed—a circumstance which may be produced by filling the lamp too high with oil.