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470 
roodation, which is marked oat on an extenfive fcale ; 
and, for the Jafl three years, both fides of the river 
have been honoured with the prefence of many of the no¬ 
bility, and other families of character and diltinftion. It 
has been afcertained that not lefs than fifteen hundred per- 
fons vifited the place for the benefit of the waters dur¬ 
ing the lalt I'eal'on, exclufive of fervants and children. 
Notwithftanding the accommodations increafe very ra¬ 
pidly, they are not equal to the demand of the company; 
but that inconvenience will be fhortly obviated by the 
extenfive and commodious houfes now erefling by the 
Lemington Building Society, and other fpirited indivi¬ 
duals. Poor invalids, who feek the benefit of the waters 
in diftreffed circumitances, are liberally relieved from a 
fund eftablifhed for that laudable purpofe. 
LEM'KENDORF, a town of Denmark, in the ifland 
of Femern : four miles weft of Borg. 
LEMLAND, a fmall ifland in the Baltic, near the 
fouth-eaft of Aland, about twenty miles in circumfe¬ 
rence. Lat. 60. 4. N. Ion. 19. 58. E. 
LEM'LEM, a country of Africa, in the internal part 
of Negroland: 500 miles ealt-fouth-eaft from Tombudtou. 
LEM'LUM, a town of the Arabian Irak : thirty-three 
miles feuth-eaft of Helleh. Lat. 31. 43. N. 
LEM'MA, f. [Gr. of va, I allume.] In mathe¬ 
matics, a propofition previoully laid down in order to clear 
the way for fome following demonftration ; and prefixed 
either to theorems, in order to render their demonftration 
lefs perplexed and intricate ; or to problems, to make 
their refolution more eafy and Ihort, Thus, to prove a 
pyramid one third of a prifm, or parallelopiped, of the 
fame bafe and height with it, the demonftration whereof 
in the ordinary way is difficult and troublefome; this 
lemma may be premifed, which is proved in the rules of 
progreffion, that the fum of the feries of the fquares, in 
numbers in arithmetical progreflion, beginning from o, 
and going on 1, 4, 9, 16, 25, 36, Sec. is always fubtriple 
of the fum of as many terms, each equal to the greateft ; 
or is always one-third of the greateft term multiplied by 
the number of terms. Alfo, to find the inflection of a 
curve line, this lemma is firft premifed, that a tangent 
may be drawn to the given curve in a given point. So 
in phyfics, to the demonftration of rauft propofitions, fucli 
lemmata as thefe are necefiary firft to be allowed; that 
there is no penetration of dimenfions; that all matter is 
divifible; and the like. As alfo in the theory of medi¬ 
cine, that where the blood circulates, there is life, &c. 
Lemma, afubjefl propofed, or title.—That’s the lemma, 
mark it. Ben Johnfori's Poetajler. 
Lemma, in pharmacy, a term ufed to exprefs the hulk 
or (hell of certain fruits, as the almond and the like; ,and, 
in general, whatever is taken off in decortication ; thus, 
the hulks of oats, barley, &c. are the lemmata of thofe 
feeds. 
LEM'MER, a feaport of Friefland, fituated near the 
ZuyderZee. In Oflober 1799, this place fubmitted to the 
Britifh fliip the Wolverene, commanded by captain Bol¬ 
ton : it is twenty miles foutli of Lewarden, and fifteen 
weft of Staveren. Lat. 52. 52. N. Ion. 5. 30. E. 
LEM'MER, f. in zoology. See Mus. 
LEM'NA, /. Duck’s Meat; in botany, a genus of 
the clafs monoecia, order diandria, natural order of inif- 
cellanete, (naiades, JuJ[.) The generic characters are— 
I. Male flower. Calyx: one-leafed, roundiffi, gaping on 
the fide, obliquely dilated outwards, obtufe, fpreading.de- 
prefled, large, entire. Corolla: none. Stamina: filaments 
two, awl-fliaped, incurved, length of the calyx; antherse 
twin, globofe. Piftillum: germ ovate; ftyle ffiort, perma¬ 
nent; ftigma obfeure. Pericarpium : abortient. II. Fe¬ 
male flower in the fame plant with the male. Calyx as 
in the male. Corolla: none. Piftillum: germ fubovate; 
ftyle fliorr, permanent; ftigma Ample. Pericarpium: 
capfule globofe with a point, one-cel!ed. Seeds fome, 
oblong, (harp on each fide, nearly the length of the cap¬ 
fule, ftriated on one fide. Ehrhart and Hedwig have feen 
L E M 
hermaphrodite flowers. —EJfenlial Character. Male : Ca¬ 
lyx one-leafed ; corolla none. Female: Calyx one-leafed5 
corolla none; ftyle one; capfule one-celled. 
Species. 1. Lemna trifulca, or ivy-leaved duck’s meat: 
leaves petioled, lanceolate. Stem dichotomous, filiform, 
divaricated, having a lanceolate leaf at the angle of the 
branches, but proliferous ones terminating the branches ; 
that is, fimilar leaves growing out of their fides at right 
angles; where thefe three leaves are conjoined, there 
flioots out a pendent radicle, with a conical papilla at its 
bafe. Linnaeus obferves, that the ftems are flatted and 
proliferous, crofting each other, and thus refembling in 
the mode of growth Cadlus opuntia, or Indian fig. Dr. 
Withering adds, that the leaf-ftalks ifiue from the edge 
of another leaf, from a fiffure parallel to the fides of the 
leaf. Native of moft parts of Europe in ditches and ftag- 
nant waters; flowering from June to September. 
2. Lemna minor, or leaft duck’s meat, or duck-weed : 
leaves feffile, flattifh on both fides, roots folitary. The 
leaves of the common duck-weed are very fmall, of a 
roundifh ovate form, collected into heaps, by twos or 
threes, and forming extenfive green plats on ftagnant wa¬ 
ters, and covering the ditches; each leaf drops a Angle 
radicle. It is common in moll part of Europe, and flow¬ 
ers from June to September; Linnaeus fays in the dog- 
days. This plant affords nourifliment not only to ducks, 
but to the frelh-water polype, Phalaena lemnata, See. 
Its quick and extenfive propagation makes it troublefome 
in fome cafes; but at the fame it mult be confidered that 
it arrefts a vaft quantity of inflammable air from putrid 
water, and converts it into vital elaftic air, adapted to re- 
fpiration. It is remarked, in the third volume of the 
Atta della Societa di Firenze, that duck-weed, in places 
where it totally covers the water, retires, or contracts it- 
feIf, as foon as a branch of the Rhus radicans is dipped 
into the water near it. If a bit of the leaf-ftalk of the 
latter be thrown into the water, it moves itfelf for fome 
time in all directions, while an oily matter ifiues fome- 
times from one end and fometimes from the other; which, 
without doubt, is the caufe of its movement. A like 
motion is obferved in other plants which emit a milky 
juice; theSchinus molleexhibits this phenomenon ftrongelt 
next to the Rhus. 
3. Lemna gibba, gibbous duck’s meat, or duck-weed: 
leaves feffile, hemifpherical underneath, roots folitary. 
This differs from the preceding in having the leaves obo- 
vate, or narrowed where they are joined together, the un¬ 
der furface flightly convex, and generally tinged with 
purple; the upper furface very convex, white, of a reti¬ 
culated fpongy appearance, and filled with water, fome- 
thing refembling the internal ftruClure of Scirpus lacuf- 
tris, but not fo regular, Roots filiform, from the centre 
of the under fide of the leaf; leaves three, four, or five, to¬ 
gether, one growing out of the edge of the other. Cap¬ 
fule two-celled, containing two feeds, fomewhat com- 
prefled, and a little deprefled in the middle, more globu¬ 
lar when farther advanced. According to Gerard and 
Hudfon, this is a mere variety of the preceding. Native 
of feveral parts of Europe, in ditches and ponds ; flower¬ 
ing in July and Auguft. 
4. Lemna polyrhiza, greater duck's meat, or duck¬ 
weed : leaves feffile, roots cluttered. The leaves of this 
are much larger than in the common fort; they are thick, 
fucculent, inflated, oblong-cordate, blunt, grooved above, 
bright green, fmooth; purple underneath; five lines long, 
and four wide. This fpecies is alfo difiinguifiied by its 
dropping packets of thick black fibres from the lower fur¬ 
face of the leaves. The flowers are the fame as in the 
preceding, but are placed differently; they are to be found 
between the duplicature of each lamina, on that fide 
where one leaf infinuates itfelf into the other. The fruit 
is larger and more flatted. Linnseus fays, it floats on the 
furface of the water on the appearance of the fwallows, 
and finks again at their difappearance. All the fpecies 
fink in the winter, and rife again in the fpring. Native 
