TIN. 



off into another pit, the copper might be feparated by iron 

 in a metallic ftate. 



Tiie leavings of tin, confiding of the (lime and tails, «. e. 

 of tin-mud and tin-gravel, are dreffed by a particular kind 

 of apparatus, for the conftruftion and ufe of which, we 

 muft refer to Pryce's Min. Corn. p. 226, &c. 



Each ilamping-mill, which has conftant work and water, 

 will employ one man and five boys ; and one hundred facks 

 are carried, ilamped, and dreffed, in the fpace of a few 

 days, at the average rate of about four-pence per fack, or 

 one guinea and a half per hundred. 



When the tin-ore is dreffed, it is divided into as many 

 fliares as tlierc are lords and proprietors. 



The next operation pertaining to tin-ore, or black tin, 

 is that of fmeltlng it. The Phoenicians, who traded to 

 Cornwall for tin in the earlier ages, probably condudled this 

 procefs by digging a hole in the ground, and flrewing the 

 ore on a charcoal fire, which perhaps was excited by a bel- 

 lows. But having no idea of confining the fire, and direft- 

 ing its force on the fubflance to be fmelted, they made no 

 ufe of furnaces, either fimple or reverberatory. Charcoal 

 was long ufed in the operation of fmclting, till at length 

 iieceflity fuggefled the introduftion of pit-coal ; and in the 

 ..fecond year of queen Anne, a patent was granted for fmelt- 

 *ing black tin with fofllle coal in iron furnaces. The inven- 

 tion of rcverberatory-furnaces built with brick, ftone, fand, 

 lime, and clay, foon followed this difcovery ; the form of 

 which, being fimple, has admitted of little improvement to 

 the prefent time. The chai'ge for one of the tin fmelting- 

 furnaces is from five to fix hundred weight of black tin, 

 well mixed with a tenth or twelfth or eighth its weight of 

 culm, which is a fpecies of coal from South Wales, that is 

 very free from fulphur. The furnace is charged through a 

 hole in its fide with a fliovel, and the tin levelled over the 

 bottom with an iron rake or paddle. The apertures are 

 then clofed, and the lire raifed to a very great ftrength, in 

 which ftate it is left for four or five hours, when the door is 

 taken off, and the whole cliarge well ftirred together. The 

 ilate of the metal is examined, and more culm thrown in if 

 neceffary ; the furnace is again clofed, and the fire kept up 

 till the end of about fix hours from its receiving the charge ; 

 when it is again examined, and if proper, it is then tapped, 

 and the metal let out into a fixed bafon made of clay, and 

 large enough to hold fomewhat more than the metal of the 

 chai"ge. The fcoria in the bottom of the furnace is raked 

 out at the mouth into a fmall pit made for this purpofe, 

 where it generally forms itfelf into a cake. When cold, it 

 is carried to the ftamping-mill, in order to feparate the 

 . globules of melted tin diffeminatcd through the fcoria or 

 flag. This, being broke by hammers to the fize of goofe- 

 eggs, is put into the firft ftamping-mill, and paffed through 

 fmall iron bars ; by which means the pillion (for fo all tin re- 

 covered out of the flags is called) of the larger fize is taken 

 out and prevented from wafte by too much ftamping. The 

 refufe of this firft ftamping is put into other ftamping-mills 

 of a fecond, third, or even fourth fize. Of the pillion, fe- 

 parated from the fcoria, all the rough or grainy parts are 

 confidered as metals, and refined accordingly, by being 

 fmelted without any flux, and the produce of this fmelting 

 refined, with the tin firft tapped. 



The tin in the bafon, or float (as it is called), as foon as 

 it comes down to a moderate heat, is laded out into the 

 moulds, in flabs or pigs of about three-fourths of a hundred 

 weight. 



The method of fmelting in Saxony and Bohemia, does 

 not differ greatly from that praftifed in Cornwall. When 

 the ore has been roafted it is waflied upon tables, to feparate 



the oxyd of iron and the oxyd of copper, which are ligliter 

 tiian tin-ore. At Alt-Saint-Jolm, llie oxyd of tin is mixed 

 with the black oxyd of iron : tiiis is feparated by a powerful 

 magnet, which is drawn over the table. That the powdered 

 oxyd of tin may not be blown away by the blaft of the 

 furnace, it is previoufly moiftened with water ; but as the 

 flame always carries away a part of the ore, a chamber is 

 conftrufted about the middle of the chimney, made of wood 

 lined with clay, where tiie powdered ore that has been driven 

 up by the flame is depofited. 



The next procefs is that of rejining. The furnace having, 

 by the fide of the fmall float now defcribed, a larger one 

 capable of holding twenty, or more blocks, is for this pur- 

 pofe fuffered to cool to a certain degree, and then charged 

 full with the flabs juft mentioned, the tap-hole being kept 

 open, fo that as the tin melts in this moderate fire, it makes 

 its exit through it into the float ; where, while running out, 

 it is frequently ftirred and toffed by a ladleful at a time held 

 arm-high, letting it fall in a ftream into the mafs of metal, 

 when the fcum which arifes is taken off. While the metal 

 already put into the furnace is melting, more is added, fo as 

 to be juft enough to fill the float with good tin : and this, 

 after being tolfed and flcimmed as before, and fuffered to 

 cool to a proper temper, is carried in iron ladles to moulds 

 holding generally fomewhat above three hundred weight 

 (then denominated block-tin), where they are marked as the 

 fmelters chufe with their houfe mark, which may be a peli- 

 can, plume of feathers, ftag, or horfe, by laying brafs or 

 iron ftamps, in the face of the blocks while the tin is in a 

 fluid ftate, and yet cool enough to fuftain the ftamping iron. 

 The blocks are then ready to be weighed, numbered, and 

 fent to the neareft coinage town to be coined. The privi- 

 leged towns for coinage of tin, were anciently Liflteard, 

 Loftwithiel, Truro, and Helfton : but foon after the Re- 

 ftoration, Penzance was added to the number ; in which laft 

 place there is every quarter more tin coined than in the 

 towns of Lilkeard, Loftwithiel, and Helfton, for a whole 

 year. When the tin is brought to be coined, the affay- 

 mafter's deputy afTays it by cutting off with a chiffel and 

 hammer a piece of one of the lower corners of the block, 

 about a pound weight, partly by cutting and partly by 

 breaking, in order to prove the roughnefs and firmnefs of 

 the metal. If it is a pure good tin, the face of the block 

 is ftamped with the duchy feal, which ftamp is a permit for 

 the owner to fell, and at the fame time an affurance that 

 the tin fo marked has been examined and found merchant- 

 able. The ftamping of this imprefTion by a hammer is coin- 

 ing the tin, and the man who does it is called the hammer- 

 man. The duchy feal is argent, a lion rampant gules, 

 crowned or, within a border garnifhed with bezants. 



The drofty part remaining in the furnace is by an increaf- 

 ing fire wholly melted, which is then tapped into the fmall 

 float, where the tin fubfiding, and the drofs rifing to the 

 top, the latter is taken off, and the tin laded into fmall flabs, 

 as at firft, to be again refined. The tin that remains in and 

 about the fcoria and drofs of the laft tappings, &c. is re- 

 covered by repeated fmeltings, till at laft, being almoft 

 entirely drained of that metal, they become what the work- 

 men generally call hard heads, and efteemed of no farther 

 value. 



M. GrofFe, in the Memoirs of the Academy of Sciences 

 of Paris, has delivered a method he had invented of fepa- 

 rating tin from lead or filver. Having tried an experiment 

 on the fcoricc of metal, which contained with the tin a large 

 quantity of filver, it feemed to him that one great ftep to- 

 ward the reparation of the filver, was the haflening of the 

 calcination of the tin, and with this view he tried a mixture 

 4 T 2 of 



