: 



MAM'KACTURK. 



LEAD-LINK. 



163 



i thioksr than u wW. must be lengthened, while iu sub- 

 i H rsduosd. by drawing it through a suoceasioii of holes in 

 pfcta, ^i-.j.ut.?^ gradually in diameter, similarly to the method 



adopted in drawing iron rods. The machinery employed for this pru- 

 COM has at different tiim-.i been much improved in its constnu-t. 

 that it u now of rare occurrence to meet with .m imperfect 



Driving Bench for I.c.ul Pipe. 



Lead Aot u made by pouring the melted metal from great height 

 into water. Thi* process was invented in 1782 by a workman named 

 Watte, reading at Bristol ; who U said to have conceived the idea in a 

 dream, and to bare proved iU practicability by pouring some melted 

 lead from the tower of the church of St. Mary Redcliffe at Bristol. 

 Having secured the invention by a patent, he sold it to parties possessed 

 of adequate capital ; and the patent having long since expired, the 

 process U now in common use. In order to give to the lead the quality 

 of asmming a more perfectly globular form in cooling, the metal is 

 previously alloyed with 2 per cent of arsenic, or with a small quantity 

 of mercury, which Utter U used in order to obviate an objection caused 

 by the poisonous quality of arsenic. Shot formed by granulation ore 

 made in a high tower, in the top of which the melting-room U built. 

 Clow to the furnace is placed a large colander or perforated plate, into 

 which a portion (determined by experiment) of the scoria produced in 

 melting the metal U placed ; after which the metal is ladled into it. Being 

 somewhat detained by the scoria, the lead is partially cooled and divided 

 into separate portions, which pan through the colander in the form of 

 globules ; then globules follow in such rapid succession as to have the 

 appearance, to a cursory observer, of a continued stream. The globules 

 fall into a vessel of water placed on the lower floor of the tower. Near 

 Newcastle, deserUid coal-pits are used instead of lofty towers. At New- 

 York, lead shot are made in a building of moderate height, with a blast 

 of air coostanUy rushing upwards ; this quickens the cooling, and the 

 shot are said to comprise a smaller number of defective globules. Under 

 any system of manufacture, however, the shot are of various sizes, and 

 a small proportion are imperfect as regards sphericity. Having been per- 

 fectly dried by artificial heat, they are sorted according to their sizes 

 by means of a aeries of sieves, the meshes of which have different 

 degrees of fineness. A sieve having the smallest mesh U first used, 

 that the amallest sized shot may pass through and be collected. What 

 remain are transferred to the sieve next in fineness, to separate shot of 

 of the wound size, and so on in succession. The process of separating 

 the imperfect shot U very simple. A shallow wooden tray is suspended 

 by cords from the ceiling of the room, and into this a certain quantity 

 of shot is put. By raising one end of the tray, and giving it a motion 

 from aid* to aide, the shot will roll about : such as are perfectly 

 spherical finding their way off the tray into a reservoir placed at its 

 lowest aid* ; while those which are of imperfect funn run against and 

 are detained by the sides of the tray, so that they can be collected in a 

 separate vtssf after the perfect shot have all run off. A very delicately 

 constructed machine is now used in some shot-works instead of this 

 tray. The shot thus sorted are then polished by putting about half 

 a ton together into an iron barrel which that quantity will nearly fill. 

 By means of a rotary movement given to the barrel, the shot are made 

 to rub against each other, and thus acquire a black colour and a lustrous 

 appearance. The finished shot, varying from Jth to ,\,th of an inch in 

 diameter, are finally tied up in bags. 



LilkanH, RriHtad, and Wnttr-ltoil are compounds, the chemical 

 ml in i of which has been noticed in connection with the chemistry of 

 lead ; w treat nan simply of a few manufacturing details. Litharge 

 is produced in the act of eupellation for extracting the silver, already 

 described. It is used in the nuking of flint-glass ; and in preparing 

 eerum salts of lead which are employed in dyeing and calico-printing ; 

 or, when mixed with coal and heated in a furnace, it may be made to 

 yisM up Ma metallic element, which U then called rejintd lead. Rtd- 

 Msf, or minium, w made by the medium of a reverberatory furnace. 

 The pigs of lead are melted in these fumaces.and while in a fluid state, 

 the metal is raked and stirred by means of an apparatus suspended 

 from a chain, and held by a workman. The stirring continues several 

 hours, by which time the metal, through imbibing oxygen, has lost its 

 fluidity, its whitish colour, and its metallic lustre, and has become 

 a grayish-yellow powder. A farther process separates a small |.ntion 

 of unchanged lead from the powder, which then becomes a yellow 

 pigment called moment ; and this massicot, by a second exposure to 

 th nrrerbsratory furnace, becomes converted into the still more useful 

 pigment red lead. M'nit-ltad forms the louis of nearly all the pigments 

 ttssd by the home-painter. It is very mwbolesome, giving rim to a 

 : called the f*itUtri cJ-c [PAttTMi'i Couc], and attempts have 



frequently been made to supersede it by other substances, but it ^ t ill 

 remains the staple article of the trade. It is a carbonate of lead, and is 

 produced in various ways; but the usual process in the Newcastle 

 district is the following. In a large square room ashes are laid on the 

 floor ; then a thick layer of tanner's spent bark ; then a series of earthen 

 pots, each containing about a pint of vinegar ; then a series of small 

 plates of sheet-lead, covering the open mouths of the vinegar-pots ; 

 then a layer of boards ; then a second layer of tan ; then a - 

 series of vinegar-pots, covered by a second series of leaden plate* and 

 so on : until a pile 20 or 30 feet high is built up. The room thus 

 filled often contains 10,000 or 12,000 pots of vinegar. . . three 



or four tons of lead; and in a large factory there may be ten or a 

 dozen of such rooms. The room is then closed, anrt U kept clo 

 many weeks. The tan gives forth heat enough to induce cli 

 action, and an intricate series of decompositions and re-compc 

 follow. The result is, that the lead combines with oxygen and carbonic 

 acid to form a flaky white substance, which, after a few more processes, 

 becomes white-lead sold either as a dry earthy substance, or as a kind 

 of thick paste ground up with linseed oil. The late Mr. 1'attinson was 

 among those who introduced substitutes for white-lead. One was an 

 oxychloride, made from a solution of chloride of lead with a solution 

 of lime, soda, or other alkali. 



In the lead trade, the imports, which are only small, art) almost 

 wholly from Spain, the produce of exceedingly rich mines situated at 

 Adra in Granada. The quantity furnished by these mines varies 

 much ; their greater or less produce has a great influence upon the 

 price of lead in every market of the world ; and at times has acted 

 injuriously upon the mine-owners in this country. The home produce 

 was about 78,000 tons of ore in 1848, yielding 55,000 tons of lead ; and 

 97,000 tons of ore in 1857, yielding 69,000 tons of lead the ratio 

 being about 70 per cent, of lead in the ore. England produces three- 

 fourths of all the lead ore raised in the United Kingdom. At the 

 prices of 1857, the lead was worth about 1.500.000/., besides the M!V,T 

 extracted from it. The Alston district, on the confines of Northum- 

 berland and Durham, yielded* the largest return in 1857 (17,000 tons); 

 but Cornwall gave the richest per-ceutoge of silver, averaging 37 ounces 

 to the ton. Tbe imports of lead (pig and sheet) in 1858, were about 

 14,000 tons. The exports in the same year were about 20,000 tons ; 

 besides 6000 tons of white lead, red lead, and litharge. 



LEAD-LINK. Ships are said to be in tuumlunji when the sea 

 bottom can be reached by a weight lowered from a ship with a line 

 attached. Of late years the depths at which this can be conveniently 

 done have increased in extent. Lead-lines are carried by evrry ship or 

 vessel afloat; and are either called Imml Una or deep tea, (or " dip sea " ) 

 Una. The hand-lead weighs usually about 7 Ibs., and its line \ .irii-.s 

 in length from 20 to 35 fathoms, or sometimes 40 fathoms, being 

 marked as follows : 



At 2 fathoms from the lead, with a strip of black leather. 

 3 with ditto notched. 



6 with a piece of white rag or bunting. 



7 ., with a piece of red rag or bunting. 



10 with a wide strap of leather with a hole in it. 



13, 15, and 17, as at 3, 5, and 7. 



20 a cord with two overhand knots. 



25 a cord with a half knot. 



30 a cord with three overhand knots. 



35 ., a cord with a half knot. 



40 ., ., ,, a cord with four overhand knots. 



The marked depths are called marks, the unmarked are called deeps. 

 Hence we say " by the mark seven," but " by the dttp nine," 4c., and 

 for portions of a fathom in shallow water we denote (say, for instance) 

 3} and 4J. by the words " quarter less four "and "and a half four," Ac. 



A good leadsman will swing the lead over hix head and tlinnv it well 

 forward, so that it may reach the bottom by the time the ship's i 

 brings it abreast the gangway, when ho dexterously feels the ground 

 and gets his " cast," and reads and sings the true depth. It is usual to 

 have a hollow in the bottom of the lead filled with till' 

 loose substances at the bottom adhere, and thow the nature uf the bed 



