We shall now give a more particular description of Argand's lamp, with re ference to figures. Pig. 1, Plate Argand's Lamp, is an upright elevation ; fig. 2, a section ; and figs. 0, 4, and 5, parts of this usefid instrument. A A (fig. 1 and 2) is a reservoir containing oil, whose shape is immaterial ; in the present instance it is that of an urn : B is a tube to convey the oil to the lamp, where it is con sumed. The lamp is composed of seve ral tubes, one within the other: the ex ternal, a a, is only a case to defend the others within it, having a small cup, b b, screwed to it at bottom, to receive the dropping of oil : at dthe tube is enlarged by a projection soldered to it, and into which the tube B delivers the oil it brings from the urn A A : e e (fig. 2) is the second tube, supported concentrical with the other by the enlargement d, which it is open to all down one side ; the oil, therefore, has free passage into this tube ; but as it is closed at bottom, and the cavity, d, tight, it cannot get in the external tube, a a ff is the internal tube, supported by being soldered to the bottom of the second, e e: another move able tube is placed between the tube e e and f f, as seen in the section (fig. 2), but better explained in a separate figure (fig. 4), where g h is the tube ; it is divided by a slit from top to bottom on the side g; on each side of this slit a small piece of brass plate, i, is soldered to support a frame, k, in which a small pinion works (as shown in fig. 2) ; this pinion gives Motion to a rack, 1, (fig. 5) bent at right angles at the lower end, and holding a short tube, or rather ring, in, on which the wick, 7Z, is held; this ring and the wick slide within the tubes g h, and out side of the internal tube,ff. its arm con necting it with the rack, 1, goes first through the slit down the side, g, of the tube (fig. 4), and next through the open ing in the side of tht tube, e e, where it communicates With the cavity d. At the top of the lamp a glass chimney, o o, is fixed, (as shown in fig. 3), where o o is the glass tube, with a small enlargement or ring at the bottom : pp is a brass ring going over the glass, and catching the rim at the bottom ; it is cut into a female screw withinside, and screwed upon another ring, r this presses against the bottom edge of the glass tube, and thus holds it fast between them.: the ring r
fits tight by friction upon the top of the tube, a a ; but so as to be easily removed when the glass is to be cleaned or taken away. The great advantage of this lamp is, that the wick is hollow, and the air brought to it, both on the inside by the tubes ff, and outside between the tubeil e e and a a, and by the rarefaction of the air in the glass chimney, a considerable draught is created, and the air forming, which is forced to pass through the flame. In the urn, A, is a contrivance to regulate the quantity of oil coming from it, that the lamp may not be overflowed : it unscrews at t; (fig. 2) and terminates below the screw in a small pipe, te closed at bottom : a hole is made in the side of this Pipe, through which the oil flows : it is closed occasionally by a' small tube sliding upon the other, v, and moved by a small handle, t, coming thrOugh the screw, t: a small hole should be drilled through the screw in the same direction as the wire of the handle, t, to supply air to this part. When the urn is to be fill ed with oil, it is unscrewed at t, and the oil poured in at the hole in tube v: the hole must then be closed, by pushing down the handle, t: the oil cannot now get out, and the urn is screwed into its place ; when the handle, t, is pushed down, the hole is opened by removing the tube, u, from before the hole in the pipe, v : the oil now runs out, the air en tering at the same hole, until it rises in • the cistern at the end of the pipe, B, above the level of the hole; the air can not now enter, and consequently the oil will not come out, until by the burning of the lamp the oil is drawn down below the hole ; a bubble of air then gets into the urn, and an equivalent drop of oil runs down: by this means, though the lamp is always plentifully supplied, yet it never runs over.