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may have their proper effect with those in authority, andthat laws so oppressive and so injurious may shortly beabolished. A greater attention to sanitary regulations willgo far to prevent the generation of disease at home; andthen, even without quarantine laws, we need have littleapprehension of contagion from abroad.

LEAD, (from the Saxon Iced.) The colour of lead is ofa bluish-white ; when tarnished, it becomes yellowish-white,then bluish, and at last bluish-black. Lustre, when untar-nished, 3; hardness, 5; and specific gravity, somewherebetween 11 and 12. According to Brisson, it was 11 "352;and a specimen tried by Gellert, which was found at Frey-burg, was estimated at ll - 445. Next to gold, platina, andmercury, it is the heaviest metal, being upwards of eleventimes heavier than an equal bulk of water. The heaviest isreckoned the best. It stains paper and the fingers. Nextto tin, it is the most fusible of all the metals. It is solublein most of the acids, though more readily so in the nitrousdiluted than the others. By exposure to the moist atmos-phere, it rusts, or oxides. It is malleable and unelastic, andits oxide is easily fusible into a transparent yellow glass.

Lead is much used in building, particularly for coverings,gutters, pipes, and in glass windows. For which uses, it iseither cast into sheets in a mould, or milled; which last,some have pretended, is the least serviceable, not only onaccount of its thinness, but also because it is so exceedinglystretched in milling, and rendered so porous and spongy, thatwhen it comes to lie in the hot sun, it is apt to shrink andcrack, and consequently will not keep out the water. Othersj have preferred the milled lead, or flatted m,etal, to the cast,

! because it is more equal, smooth, and solid,i The lead used by glaziers is first cast into slender rods,

I twelve or fourteen inches long, called canes; and these, beingj afterwards drawn through their vice, come to have a groovei on either side for the panes of class; and this they calll turned lead.

! The method of paling or soldering lead for fitting on of| embossed figures, &c., is by laying the part whereon thefigure is to be paled, horizontally, and strewing bn it somej pulverized resin; under this they place a chafing-dish of: coals till such time as the resin becomes reddish, and rises inj pimples; then the figure is applied, and some soft solderrubbed into the jointings ; when this is done, the figure willbe paled on, and as firm as if it had been cast on. For otheruses in building, see the article Sheet Lead.

LEAN-TO, a small building, with a shed-roof attached toa larger one.

LEAVER. See Lever.

Leaver Boards. See Lever Boards.j LEAVES, a representation in marble, stone, brass, wood,j or other material, of natural leaves. See Ornament.

LEDGE, a surface on which to support a body in motion,or to support a body at rest.

The ledges of a door are the narrow surfaces wrought uponthe jambs and soffit parallel to the wall, in order to stop thedoor, so that when the door is shut, the ledges coincide withthe surface of the door.

The ledges of a door are, therefore, one of the sides of therebate, each rebate having only two sides. In temporaryworks the ledges of doors are formed by fillets.

LEDGEMENT, the development of a surface, or thesurface of a body stretched out on a plane, so that thedimensions of the different sides may easily be ascertained.

LEDGERS, in scaffolding for brick buildings, the hori-zontal pieces of timber parallel to the wall, fastened to thestandards by cords, in order to support the put-logs, on whichare laid the boards for working upon.

LEGAL COLUMN, see Column.

LEGS, of a right-angled triangle, the two perpendieulasides. ,

Legs, of an hyperbola, the two parts on each side of t0vertex.

LENGTH (from the Saxon leng), the greatest extensioof a body. In a right prism, the length is the distancebetween the ends : in a right pyramid, or cone, the leng 1is the distance between the vertex and the base.

LENGTHENING, of timber, is the method of join 10 ®several beams, so as to form a long beam of any gi v ' elength. See Scarf.

LESBIUM MARMOR, a name given by the ancients 10a species of marble of a bluish white, sometimes used *°vases, and other ornamental works, but principally in t0walls of public buildings.

LEVEL, a mathematical instrument, used for drawingline parallel to the horizon and continuing it out at pleasure*and by this means, for finding the true level, or the differenceof ascent or descent between any two places, for convey 111 *water, levelling the surface of floors, and for various ot° epurposes in architecture, hydraulics, surveying, &c.

Level, Carpenter's, consists of a long rule, straight on 1lower edge, about ten or twelve feet in length, with a ^upright piece fixed to its upper edge, perpendicular to, a °in the middle of the length, having its sides in the same p ia °with those of the rule, and a straight line drawn on °°of its sides perpendicular to the straight edge of the r ule jThis standing piece is generally mortised into the other, a °.^firmly braced on each side, in order to secure it from aC , cldents, and has its upper end kerfed in three places,through the perpendicular line, and on each side.straight edge of the transverse piece has a hole or notch cout on the under side, equal on each side of the perpencular line. A plummet is suspended by a string from 1middle kerf at the top of the standing piece, so that, ' v ° , flhanging at full length, it may vibrate freely in the, 0 jor notch. When the straight edge of the level is apP 1 jfto two distant points, with its two sides placed verticall^^the plummet hangs freely, and coincides with the strata .j,line on the standing piece, the two points are level; h ut , l6not, suppose one of the points to be at the given height; 1other point must be lowered or heightened, as the case n^require, until the thread is brought to a coincidence with fperpendicular line. By two points is meant two surfacescontact, as two blocks of wood, or chips, or the upper eu»of two distant beams. g

The use of the level in carpentry, is to lay the upper .of joists in naked flooring horizontal, by first levelling 1 ibeams as remote from each other as the length of the ^will allow; the plummet may then be taken off, and the i . gbe used as a straight edge. In the levelling of joists,best to make two remote joists first level in themselves, ^is, each throughout its own length, then the two level 1each other ; after this, bring one end of the interm® 0 ^joists straight with the two which have been levelled j ]tthe other end in the same manner; then try the 8tr °. ,i ’ a jiedge longitudinally on each intermediate joist, and sueare found to be hollow must be furred up straight. flll

To adjust the level .—Place it in its vertical situation ,two pins or blocks of wood ; then, if the plummet, hn°o o[ ,freely, settle upon the line on the standing piece, (or, 11 j 0one end being raised, or the other end lowered, to make 1so,) turn the level end for end, and if the plummet fallthe line, the level is just; but- if not, the bottom edge ube shot straight, and as much taken off the one end aS 'may think necessary; then trying the level first one