LAMP, ARGAND'S. 
held even at the distance of an inch below 
the lower aperture of the cylinder ; and 
there is also a certain length of wick at 
which the effect of the lamp is strongest. 
If the wick be very short, the flame, though 
white and brilliant, emits a disagreeable 
and pale kind of light; and if very long, the 
upper part becomes brown, and smoke is 
emitted. The saving of expense in the use 
of this instrument for common purposes is 
very considerable. By some experiments 
it appears, that the lamp will continue to 
burn three hours for the value of one penny ; 
and the following was the result of the 
comparison between the light emitted by it 
and that of a candle. The latter having 
been suffered to burn so long without snuf- 
fing, that large lumps of coaly matter were 
formed upon the wick, gave a light at 24 
inches distance equal to the lamp at 129 
inches: whence it appeared, that the light 
of the lamp was equal to 28 candles in this 
state. On snuffing the candle, however, its 
light was so much augmented, that it be- 
came necessary to remove it to the distance 
of 67 inches, before its light became equal 
to that of the lamp at 129 inches : whence 
it was concluded, that the light of the lamp 
was somewhat less than that of four candles 
fresh snuffed. At another trial, in which 
the lamp was placed at the distance of 131 j 
inches, and a candle at the distance of 55 
inches, the lights were equal. In these ex- 
periments the candles made use of were 
10| inches long, and 2,^ inches in diameter. 
When the candle was newly snuffed it ap- 
peared to have the advantage ; but the 
lamp soon got the superiority ; and on the 
whole it was concluded, that the lamp is at 
least equivalent to half a dozen of tallow 
candles, of six in the pound ; the expense 
of the one being only 2id. and the other Sd. 
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; tig. 2, a sec- 
tion ; and tigs. 3, 4, and 5, parts of this use- 
ful instrument. A A (fig. 1 and 2) is a re- 
servoir containing oil, whose shape is imma- 
terial ; in the present instance it is that of 
an urn : B is a tube to convey the oil to the 
lamp, where it is consumed. The lamp is 
composed of several tubes, one within the 
other : the external, a a, is only a case to 
defend the others within it, having a small 
cup, b h, screwed to it at bottom, to 
receive the dropping of oil: at d 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 tlie 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 moveable tube is placed be- 
tween the tube e e and f f, as seen in the 
section (fig. 2), but better e.Kplained 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 solder- 
ed to support a frame, fc, in which a small 
pinion works (as shewn in fig. 2) ; this pi- 
nion gives motion to a rack, I, (fig. 5) bent 
at right angles at the lower end, and hold- 
ing a short tube, or rather ring, m, on which 
the wick, m, is held ; this ring and the wick 
slides within the tubes g ft, and outside of 
the internal tube,//, its arm connecting it 
with the rack, I, goes first through the slit 
down the side, g, of the tube (fig. 4), and 
next througlrthe opening in the side of the 
tube, e c, where it communicates with the ca- 
vity d. At the top of the lamp aglass chimney, 
0 0 , 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 . 
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 ea- 
sily 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 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. lu 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 f, (fig, 2) and ter- 
minates 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, coming through the screw, t : a 
Small bole should be drilled through the 
