LAM 
L A M 
der, in the polyandria class of plants, and in 
the natural method ranking with those of 
which the order is doubtful. The corolla is 
pentapetalous, or none; the calyx is penta- 
phyllous; the fruit is unilocular and trigonal; 
the seeds have a pulpy ai illus or coat. There 
are four species, natives of America. One of 
them, the apetala, or gum-wood, Dr. Wright 
informs us, is very common in the woodlands 
and copses of Jamaica, where it rises to a 
considerable height and thickness. Pieces of 
the trunk or branches, suspended in the heat 
of the sun, discharge a clear turpentine or 
balsam, which concretes into a white resin, 
and which seems to be the same as gum san- 
darach. Pounce is there made of it ; and 
our author is of opinion t hat it might be use- 
ful in medicine like other gums of the same 
nature: 
LAGERSTR.OEMIA, a genus of the mo- 
nogvnia order, in the polyandria class of 
plants. The corolla is hexapetalous, and 
curled; the calyx sexful, and campanulated; 
there are many stamina, and of these the six 
exterior ones thicker than tire rest, and long- 
er than the petals. There are four species, 
trees of the East Indies. 
LAGOECIA, a genus of the monogynia 
order, in the pentandria class of plants, t he 
involucrum is universal and partial ; the pe- 
tals bifid; the seeds solitary, inferior. There 
is one species, wild cummin, an annual, of the 
Levant. 
LAGUNEA, a genus of the class and or- 
der monadelphia polyandria. The calyx is 
simple, five-cusped ; style simple ; stigma 
peltated ; capsule five-celled, five-valved. 
There are three species, shrubs of the East 
Indies and Surinam. 
LAGURUS, a genus of the digynia or- 
der, in the triandria class of plants, and in 
the natural method ranking under the fourth 
order, gramma. The calyx is bivalved with 
a villous awn, the exterior petal of the co- 
rolla terminated by two awns, with a third on 
its back retorted. There is one species, a 
grass of the south of Europe. 
LAKES, certain colours made by com- 
bining the colouring matter of cochineal, or 
of certain vegetables, with pure alumine, 
or with oxide of tin, zinc, &c. 
LAMA, the sovereign pontiff, or rather 
god, of the Asiatic Tartars, inhabiting the 
country of Barantola. The lama is not only 
adored by the inhabitants of the country, but 
also by the kings of Tartary, who send him 
rich presents, and go in pilgrimage to pay 
him adoration, calling him lama-congiu, i. e. 
God the everlasting father of heaven. lie is 
never to be seen but in a secret place of his 
palace, amidst a great number of lamps, sit- 
ting cross-legged upon a cushion, and adorned 
all over with gold and precious stones ; where, 
at a distance, they prostrate themselves be- 
fore him, it not being lawful for any to kiss 
even his feet. He is called the great lama, 
or lama of lamas, that is, priest of priests. 
And to persuade the people that he is im- 
mortal, the interior priests, when lie dies, 
substitute another in his stead, and so conti- 
nue to cheat from generation to generation. 
These priests persuade the people that the 
lama was raised from death many hundred 
years ago, that he has lived ever since, and will 
continue to live for ever* 
LAM 
LAMINAE, in physiology, the thin plates I 
of which many substances consist. 
LAMIUM, dead-nettle, a genus of the 
gvmnospermia order, in thejdidynamia class 
ot plants, and in the naturaFmethod ranking 
under the 42d order, verticillata*. The upper 
lip of the corolla is entire, arched, the under 
lip bilobous ; the throat with a dent or tooth 
on each side of the margin. There are 13 
species, of which only two, viz. the album, 
white archangel or dead-nettle, and the pur- 
pureum, or red archangel, deserve notice. 
1 lie flowers of the first, which appear in 
April and May, have been particularly cele- 
brated in uterine fluors, and other female 
weaknesses, and also in disorders of the lungs ; 
but they appear to be of very weak virtue. 
The young leaves of both species are boiled 
and eaten in some places like greens. 
LAMP, a vessel containing oil, with a 
lighted wick ; of which there an indefinite 
number made of various constructions for va- 
rious purposes. We shall particularly notice 
Argand’s lamp, and an improvement made 
upon it. 
Argand’s lamp is a very ingenious contriv- 
ance, and is the invention of a citizen of Ge- 
neva. '1 he principle on which the superiority 
of the lamp depends, is the admission of a 
larger quantity of air to the flame than can 
be done in the common way. This is ac- 
complished by making the wick of a circular 
form, by which means a current of air rushes 
through the cylinder on which it is placed, 
with grea,t force ; and, along with that which 
has access to the outside, excites the flame to 
such a degree that the smoke is entirely con- 
sumed. Thus both the light and heat are 
prodigiously increased, at the same time that 
there is a very considerable saving in the ex- 
pence of oil, the consumption of the inflam- 
mable matter being exceedingly augmented 
bv the quantity of air admitted to the flame ; 
so that what in common lamps is dissipated 
in smoke is here converted into a brilliant 
flame. 
This lamp is now very much in use, and is 
consequently well known. 
We shall now describe an improvement o-f 
this neat invention. See Plate Lamp, &c; 
The upper compartment of the Plate repre- 
sents an improved construction of Argand ! s 
lamp. A, fig. 1, is the reservoir for the oil, 
which unscrews at B; in order to- fill it the 
oil is poured in at a hole a, fig. 4, in the 
lower end of the reservoir, which is covered, 
when the lamp is not burning, by a sliding 
collar, b, drawn up by a handle, d, which 
comes through- a hole" in the screw e, by 
which the reservoir is screwed' in the short 
tube, E, fig. 1 : there being no vent-holes in 
the upper part of the reservoir, A, to admit 
the air as the oil runs out, a bubble of air 
must enter the hole a, fig. 4, to supply the 
place of every chop of oil that comes out, 
when the reservoir, A, is screwed to the tube, 
E; the collar. In, being down, the oil runs 
out (the air being admitted from without 
through a small hole,/), till E is filled above 
the level of the hole, a, which prevents more 
air getting in ; it remains in this state till by 
the burning of the lamp the oil is drawn down 
beneath the hole a, when it is filled again as 
before ; by this means the lamp is always well 
supplied, but never Overstocked with oil. 
From the bottom of the tube, E, lig. 1, the 
oil is conveyed by a pipe, D, to the lamp,. 
47 
the constitution of which is best explained in 
fig. 2 ; EF is the external tube of brass, which 
is supplied with oil by tbe pipeD; in the 
centre of this another tube, GG, is soldered, 
which is open at both ends : between these 
tubes is a cylinder of slightly wove cotton, 
gg, called the wick ; this is fastened to a small 
cylinder of brass, hh (shewn separately in tig. 
3), which can be moved down and up as the 
wick burns. The wick is lowered or raised 
by turning round the cylinder, HH (shewn 
separately in figs. 5), by means of its rim, 11, 
fastened to the cylinder, I1H, by three small 
rods, ii ; the cylinder, HH, iig‘. 5, has a spi- 
ral groove, kk, cut obliquely round it : the 
cylinder, hh, figs. 2 and 3, which goes within 
the cylinder, HH, has a small stub, /, pro* 
jeering from it, which works into the groove, 
kk, fig. 5 ; the leaf, /, is long enough to pro- 
ject a small distance through the groove, k/c, 
and when in its place takes against a. small 
bead, n, fig. 2, fixed withinside the cylinder, 
l’ 1' , so as to prevent.its turning,, when I1H is 
turned by its rim, II. By the above arrange- 
ment it is evident, that when the cylinder, 
HH, fig. 5,. is turned' round, and h is pre- 
vented from, turning, the sides of the groove, 
k, will act as an inclined, plane against the 
stub, /, and raise the cylinder h down or lip, 
and the cotton, wick, with it. The rim, 11, 
figs. 1,2, and 5* has an ornamented border, L, 
round it, which, serves to secure the glass 
chimney, o, from being overthrown. To. 
prevent the cylinder, HII, from being lifted 
out by accident, it has'a rim„o, figs. 2 and 5, 
at the lower end, cut through in one place to 
allow it t<? pass down by the bead, n ; when 
it is below the end of the bead it cannot be 
raised, unless the notch in the rim, o, cor- 
responds with tiiu bead. When the wick, 
gg, figs. 1 and 5, is lighted,, it rarefies the air 
in the glass chimney, O, and causes a draught 
through the tube, GG, to supply the inside of 
the wick, and aLo under the edge of the glass 
chimney to- supply the outside: as the wick 
burns down it can be raised from time to 
rime by turning the rim, I, as before describ- 
ed.. 1 he tube, FF, is always nearly full of. 
oil, brought by the pipe, D. When it is re- 
quired to put in a new wick, the glass cliim- 
ney, O, is lifted off ; the tube, hh, is screw- 
ed up to the top ; by turning the rim, II, the 
tube, lig. 3, is then taken out, the old wick- 
pulled ofl, and a new one is put round the 
small part, m, ot the tube, which* is then put 
in again, and screwed down to* the proper 
depth for lighting the v ick- 
Rolling- Lamp, a machine, AB(seePI. Mis- 
cp l; fig* 145.) with two moveable circles,. 
DE, I’G, within; whose common centre 
of mot ion and gravity is at K, where their axes, 
of motion cross one another. If the lamp, 
KC, made pretty heavy, and moveable about 
its axis, H I, and whose’centre. of gravity is at 
C, be fitted within the inner- circle, the com- 
mon centre ot gravity of the whole machina 
will fall between K and C ; and by reason of 
the pivots A, B, D, E, H, I, will 'be always 
at liberty to descend: hence, though the 
whole machine be rolled along the ground, or 
moved in any manner, the flame will always: 
be uppermost, and the oil cannot spill. 
It is in this manner they hang the com- 
pass at sea; and thus should alf the inooiir- 
lanterns be made that are carried lav tyre 
coaches, chaises, and the like. 
