LAMP, ARGAND'S. 



inches : whence It appeared, that the 

 light of the lamp was equal to 28 can- 

 dles in this state. On snuffing 1 the can- 

 dle, however, its light was so much aug- 

 mented, that it became necessary to re- 

 move it to the distance of 67 inches, be- 

 fore its light became equal to that of the 

 lamp at 129 inches : whence it was con- 

 cluded, that the light of the lamp was some- 

 what less than that of four candles fresh 

 snuffed. At another trial, in which the 

 lamp was placed at the distance of 13 1^- 

 inches, and a candle at the distance of 55 

 inches, the lights were equal. In these 

 experiments the candles made use of 

 were 10 inches long, and 2^ inches in 

 diameter. When the candle was newly 

 snuiTed it appeared to have the advan- 

 tage; but the lamp soon got the supe- 

 riority; and on the whole it was conclud- 

 ed, that the lamp is at least equivalent to 

 half a dozen of tallow candles, of six in 

 the pound; the expense of the one be- 

 ing only 2 \d. and the other 8d. in seven 

 hours. 



We shall now give a more particular 

 description of Argand's lamp, with re- 

 ference to figures. Fig-. 1, Plate Argand's 

 Lamp, is an upright elevation ; fig. 2, a 

 section ; and figs. 3, 4, and 5, parts of this 

 useful instrument. A A (fig. 1 and 2) 

 is a reservoir containing oil, whose shape 

 3s 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 t 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 the 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 :ffh 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//, as seen in the section (fig. 2), but 

 belter 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 ,f; 

 on each side of this slit a small piece of 

 brass plate, /, is soldered to support a 

 frame, A?, in which a small pinion works 

 (as shewn in fief. 2> ; this -pinion crive-s 



VOL IV 



motion to a rack, /, (fig. 5) bent at right 

 angles at the lower end, and holding a 

 short tube, or rather ring, m, on which 

 the wick, n, is held ; this ring and the 

 wick slide within the tubes g h, and out- 

 side of the internal tube,//, its arm con- 

 necting it witli the rack, /, goes, first 

 through the slit down the side, g; of the 

 tube (fig. 4), and next through the open- 

 ing in the side of the tube, e e, where it 

 communicates with the cavity d. At the 

 top of the lamp a glass chimney, o o, is 

 fixed, (as shewn 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 withinsidc, and screwed upon 

 another ring, r . this presses against the 

 bottom edge of the glass tube, and thus 

 holds it f:ist 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// and outside between the tubes 

 c 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 t (fig. 2) and terminates 

 below the screw in a small pipe, v } 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, corning through the 

 screw, t : a small hole should be. drilled 

 tlrrough 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, f, 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, 13, 

 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 

 H 



