74.] LEA workmen to the windward, v/hen they opfu bales of Turkey cotton, wliiqli have not been unpacked since thiy were shipped, perhaps during the jtrevalence of the plague. Iliis easy kind of attention will not occasion great loss of time, or any additional expc-'nce3 vvhile it doubtless tends to avert impending, though distant danger, and to pre- vent the introduction of that dread- ful scourge, the plague. LEA, a measuie used in some parts of England, to express a cer- tain quantity of yarn. — ^The statute 22 Car. JI. directs a lea of yarn, at Kidderminster, to contain two hundred threads, on reels that are four yards in circumference. LEAD, one of the imperfe6i metals, is of a dull while, inclin- ing to a blue colour ; and, though the, least ductile and sonorous, it is The heavieiitof metallic bodies, ex- cept'ng mercury, gold, and platina. Ijead ,is found in various coun- tries; but it abounds in England, fspeciaily in the counties of Derby and Devon. When dug out of the earth, it is crushed in a mill, and snjelted in a manner similar to iron-ore, of whicii we have already treated. A patent was granted in 1/79) to Mr. W. KoE, for his new -in- vented process of extracting suL- phiir from poor lead ores, and ren- dering these as valuable, and sale- able, as any other ores of this metal.— As this patent is now ex- pired, and tl e principle c-f the in- ventor is equally simple and inge- liious, we trust it is, or will be, genera'ly adopted in our amtlting- liouse,s : the inquisitive reader will lind it.luUy specitied in the 6th vol. of the " Itcperivry of Jrts a7id J^ilanq/'aiiures." Lead is cn^ployed in making va- LEA rious vessels, such as cisterns for water, large boilers for chemical purposes, &c. Conbiderab'e quan- tities are likewise used in the cast- ing of shot, for which' a patent was granted in 17&2, to Mr. Villi.m V^ATTs, in consequence of his invention of gra:iu!aling lead solid throughout, without those imper- ledions which other kinds ot shot usually present on their surface. — The patentee dire6ts 20 cwt. of soft pig-lead to be melted in an iron pot, round the edge oi which, a peck of coal-a.shes is to be strew- ed upon the surface of the metal, so as to leave the middle oi the latter exposed. Forty pounds of arsenic are next to be added to the uncovered lead, and the pot closely shut: the edges of the lid being carefully luted with mortar, clay, . or otiier cement, in order to pre- vent the evaporation of the arstnic. A bri.sk tire is then kindled, so that the two substances may be properly incorporated; when the metal ought to be skimmed and laded into mculd.s, that it may cool in the torm of ingots or bars,
hich, v/hen cold, are called sing,
or poisoned metal. — 20 cwt. of soft pig-lead (according to the quantity ot shot intended tu be mauutactur- ed) are next to be melted in the manner above direded; and, when it is completely liquttied, one of the ingots or bars of slag must be added : as. soon as the v%hole i.s ctmbined, a bu.all quantity of the • liquid metal is to be ta. en out With a ladle, and dropped Irom a height of about two lect into the waicr. It the shot be not perteCtly round, it will be neces.sary to add Uiore slag, till it drops in a globu- lar form. Tl e metal is next skim- med, and the scum poured into an iron or copper frame perlorated witk
