TIN. 



of thf famplf triiT. After the tin is llius cleaned, it is 

 dried ; and if there he as much blaclc tin as will cover a 

 (hilling, or equal to the weight of a (hilling, it is called a 

 jhillin'; van, which is not rich ; but if the tan will cover or 

 equal the weight of a crown-piece, it is good tin-ftuft, and 

 called a crown van. The (liilling van, the tinners fay, will 

 produce one hundred avoirdupois weight of block or white 

 tin ; and the crown van will yield five hundred weight of 

 block tin, for every hundred facks in meafure of the rcfpec- 

 tive doles from which the fample or van was taken, and fo 

 ill proportion, to the richeft tin-duff, c^Wcd. f cove, which 

 is reckonc<I at the rate of ten thoufand of white tin-metal 

 for every hundred facks. But a better judgment may be 

 formed from the meafure of a wine half-pint, than from a 

 handful, which is indeed accounted a half pint. When the 

 tin, thus meafured, is reduced clean, and to a proper fize, 

 by ufing a large fhovel, and taking off the fized tin on an- 

 other (hovel, the van is dried in a fhovel upon the fire, and 

 then weighed by pennyweights and grains ; and for every 

 pennyweight and a half the van weighs, the produce will 

 be one hundred weight of black tin for every hundied facks 

 of tin-duff; and for three pennyweights, two hundred weight, 

 &c. in the fame proportion ; and if it be tin worth ten for 

 twenty, or one for two, then the tin-ftuff is valued at five 

 hundred weight of block or white tin for every hundred 

 facks : if it be worth twelve for twenty, the (luff is valued 

 at fix hundred weight of white tin a hundred ; or if it be 

 worth only eight for twenty, it is only valued at four hun- 

 dred weight of white tin a hundred, &c. This black tin is 

 rather of a liver colour, though called black in contra- 

 diftinclion from white tin, or the metal produced from this 

 black ore : it is very heavy, and may in general be com- 

 puted to hold one-half clean metal, and fome of it will pro- 

 duce thirteen, or even fourteen parts in twenty ; whence 

 the mode of expreffing fo much white tin for twenty of 

 black tin, t. e. eight for twenty, ten for twenty, twelve 

 for twenty, &c. Thus, if the van of one hundred facks 

 of tin-ftuff weighs fix pennyweights, being four hundred 

 weight of black tin at twelve for twenty, the white tin or 

 metal mud be two hundred weight one quarter fixteen 

 pounds. 



In this method of fampling, the tinners form a near con- 

 jedure of the quantity of white tin which their doles of 

 tin-ftuff will produce at the fmclting-lioufe, when it is 

 dreffed, and brought into black tin. But if the black tin 

 IS combined with any bad mixture, as of mock-lead, copper, 

 or mundic, after the van is bruifed fine and wa(hed, they 

 lay the (hovel over the fire, and burn the black tin, ftirring 

 it continually, till it has done fmoaking : they then wa(h 

 it again on the (hovel, and thus the heterogeneous matter, 

 becoming light by being burnt, is carried off by the water : 

 for when black tin is calcined or burnt, it flill retains its 

 fpccific gravity ; but copper, lead, and other crude mine- 

 rals, become much lighter by torrefaftion, and are eafily 

 f^parated from tlie tin by water. In the drclTmg and ma- 

 nagement of tin by ftamping, £cc. there are obtained two 

 forts of black tin, -uiz. the crop and rough, or the crop 

 and leavings of tin. The firft is the prime tin : immedi- 

 ately feparable from the bafer parts by its fuperior weight 

 and richnefs. The latter is that which is carried off, and 

 mixed with the Ughter earthy parts, by being under fize, 

 and, therefore, more eafily carried off by the water. 



The tin-iluff, after this previous preparation and adjuft- 

 ment, is carried to the ftamping-mill, in order to be dreffed 

 or pounded. 



This operation of pounding in the ftamping-mill is efl"en- 

 tial to the complete feparation of the ore from the matrix. 



through which it is difleminated. If full of flimc, it i; 

 thrown into a ])it, called a Imdilh; to wa(h away the earth) 

 matter, and render the ftamping more free, without choak- 

 ing the grates. The ore is fliovelled into a kind of flopinp 

 canal of^timber, called the />;?/}, whence it Hides by its owi 

 weight, and the alTiftance of a fmall ftream of water, intr 

 the box where the lifters work : the lifters are r.uted by ; 

 water-wheel, and are armed at the bottom with large 

 maffes of iron, weighing nearly two hundred weight each : 

 thefe pound or ftamp the ore fufficiently to enable it to 

 pafs through the holes of an iron grate fixed at one end 

 of the box. To affift its pulverization, a rill of water keeps 

 it conftantly wet, and it is carried by a fmall gutter into 

 the fire -pit, where it makes its firft depofition ; the lighter 

 particles running forward with the water into the middle 

 pit, then into a third, where what is called i\\e Jl'ime fettles 

 (See Drejfing of Or-es, and Buddle. ) From thefe pits 

 the ore is carried to the keeve, which is a large vat containing 

 water; in which it is farther purified by an operation 

 itvmeA pncklng, and which confifts in beating the upper 

 part of the contents with mallets for fome minutes, by 

 which the lighter particles are kept fufpended, whilft the 

 tin-ore, from its great fpecific gravity, fubfides. The wafte 

 is flcimmed and laid by, to be again huddled, under the. 

 name of ihs fihnpings . The tin is fifted through a copper- 

 bottom fieve into another keeve of water, by which the 

 gravelly wafte ftill remaining is feparated from the clean tin ; 

 and the tin that runs through the fieve, if it requires no 

 farther huddling, may be cleaned by repeatedly toffing and 

 packing it as before. If it be necelfary to buddle it again 

 after it is fifted, let it be huddled and diftributed in three 

 parts, viz. the crop or pureft, the creafe or next in purity, 

 and the hind-creafe or tail, which is the moft impure. The! 

 crop is to be cleanfed by tolling, &c. and the creafe mull 

 be huddled again, and out of this mull be referved as much 

 as may be cleanfed by toffing and packing. The remainder 

 muft be cleanfed by an operation called dilLughing, from 

 dilleugh, to let go, or fend away. A dilleugher is a large' 

 fine hair-fieve, which the drelTer holds in a keeve one-third 

 full of water, into which the tin is thrown by a fhovelful 

 at a time, and which is fliook fo as to put the tin into mo- , 

 tion : one fide of this dilleugher is dipped in water, and 

 raifed again in fuch a manner, that the wafte may run over, 

 which is laid afide to mix with the fliimpings, to make the 

 famples of low value, called the rough [or row) tin. This 

 ufually undergoes another operation, in which, by a rill of" 

 water paffing over the buddle in which it is placed, it is 

 farther cleanied, and then dilleughed, fo as to be fit to mix 

 with the crop-tin. 



Upon the fame mechanical principle of feparation, the 

 tinner is capable of eftimating the value of a fample of ore. 

 For this purpofe, the pounded tin-ore, or tin-ftuff, as it is 

 called, is placed on a ftiovel and wafhed under a ftream, till 

 the impure earthy parts are carried off by the water from 

 its fides, when, by a particular and dexterous motion, not 

 eafily defcribed, all the metallic particles are collefted to- 

 gether on the fore-part of the (hovel : this operation is 

 called vanning, which we have already defcribed. 



When the tin-ore is contaminated with the different pyri- 

 tous ores of copper, arfenic, and iron, it is firft roafted in 

 a burning-houfe, and then wafhed in water, by which means 

 the tin, which is heavy, is eafily feparated. 



By this procefs, as at prefent condufted in Cornwall, a 

 confiderable quantity of copper is loft ; for being converted 

 into fulphate of copper, which is foluble in water, it is loft 

 by waftiing ; whereas, if the roafted ore were fuffered to 

 remain in a clofe pit for a few days, and the water drawn 



off 



