LIB 
line, red, or beam, supported in a single 
point on a fulcrum or prop, and used for 
the raising of weights; being either void of 
weight itself, or at least having such a 
weight as may be commodiously counter- 
balanced. 
The lever is the first of those called me- 
chanical powers, or simple machines, as 
being of all others the most simple ; and 
is chiefly applied for raising weights to 
small heights. See Mechanics. 
LEVISANUS, in botany, so called from 
the Rev. Mr. Lewis, a genus of the Pentan- 
dria Monogynia class and order. Essential 
character: flowers aggregate; calyx one- 
leafed, superior, five-cleft; corolla five pe- 
talled, superior ; filaments inserted into the 
base of the perianth ; styles two, conjoined ; 
berry two celled ; seeds five or six, com- 
pressed. There are five species, which are 
all shrubs, and natives of the Cape of Good 
Hope. 
LEYSERA, in botany, a genus of the 
Syngenesia Polygamia Superflua class and 
order. Natural order of Compositse Dis- 
coideee. Corymbifer®, Jussieu. Essential 
character : calyx scariose ; down chafiy ; in 
the disk feathery also ; receptacle subpa- 
leaceous. There are three species. 
LEY, or lees, a term usually applied to 
any alkaline solution made by levigating 
any ashes that contain an alkali. Soap- 
lees is an alkali used by soap-boilers, or 
potash or soda in solution, and made caustic 
by lime. Lees of wine are the refuse, or 
sediment, that deposits from wine by stand- 
ing quiet. 
LEYDEN phial, in electricity, is a glass 
phial or jar, coated both within and with- 
out with tin foil, or other conducting sub- 
stance, that it may be charged, and em- 
ployed in a variety of experiments. Flat 
glass, or glass of any shape, may be used in 
the same way. 
LIATRIS, in botany, a genus of the Syn- 
genesia Polygamia iEqnalis class and order. 
Natural order of Composit® Capital®. 
Cinarocephal®, Jussieu. Essential charac- 
ter : calyx oblong, imbricate, awnless, co- 
loured; down feathered, coloured; recep- 
tacle naked, hollow, dotted. There are 
eight species. 
LIBELLULA, in natural history, dragon- 
fly, a genus of insects of the order Neurop- 
tera. Mouth armed with jaws, more than 
two in number; lip trifid; antenn® very 
thin, filiform, and shorter than the thorax ; 
wings expanded; tail of the male insect 
furnished with a forked process. There 
LIB 
are about sixty species, divided into two 
families. A. wings expanded when at rest. 
B. wings erect when at rest ; eyes distinct ; 
outer divisions of the lip bifid. The whole 
tribe of the libellula are remarkable for 
being ravenous : they are usually to be seen 
hovering over stagnant waters, and may, in 
the middle of the day, be observed flying 
with great rapidity in pursuit of the smaller 
insects. These brilliant and beautiful ani- 
mals were once, and for a considerable time, 
inliabitants of the water : in that state, as 
larva, they are six-footed, active, and fur- 
nished with an articulate forcipated mouth. 
They prey upon aquatic insects, and the 
larva of others: the pupa resembles the 
larva, but has the rudiments of wings. 
The most remarkable of the English species 
is the L. varia, or great variegated libellula, 
which makes its appearance towards the 
decline of summer, and is an animal of sin- 
gular beauty. Its length is about three 
inches; and the wings, when expanded, 
measure nearly four inches from tip to tip. 
The female libellula drops her eggs in the 
water, which, on account of their specific 
gravity, sink to the bottom : after a certain 
period they are hatched into larv®, having 
a singular and disagreeable aspect: they 
cast their skins several times before they 
arrive at their full size, and are of a dusky 
brown colour : the rudiments of the future 
wings appear on the back of such as are 
advanced to the pupa state in the form of 
oblong scales, and the head is armed with a 
singular organ for seizing its prey. They 
continue in the larva and pupa state two 
years; when having attained to their full 
size, they prepare for their ultimate change, 
and creeping up the stem of some water 
plant, and grasping it with their feet, they 
make an efibrt, by which the skin of the 
back and head is forced open, and the en- 
closed libellula gradually emerges. This 
process takes place in a morning, and dur- 
ing a bright sunshine. The remainder of 
the animal’s life is short, the frosts of autumn 
destroying them all. “ It is impossible,” 
says Dr. Shaw, “ not to be struck with ad- 
miration on contemplating the changes of 
the libellula, which, while an inhabitant of 
the water, would perish by any long expo- 
sure to the air, while the complete animal, 
once escaped from the pupa, would as ef- 
fectually be destroyed by submersion under 
water, of which not an hour before it was 
the legitimate inhabitant.” In this, and 
other species of the libellula tribe, the 
structure of the eye is deserving of notice. 
