TIN. 



In the thirty-third year of Edward I. the above charter 

 feems to have been confirmed, and the tinners of Cornwall 

 were made a dittinft body from thofe of Devonfliire, before 

 which time the tinners of both counties were aceullonicd to 

 meet on Hingfton-Hill every feventh or eighth year, to con- 

 cert the common intereft of both parties. Two eoinasjcs 

 of tin yearly were alfo granted by this charter, and the 

 tinners had the liberty of felling their own tin, imlefs the 

 king infilled on buymg it himfelf. Other laws and regu- 

 lations for the encouragement and protection of the miners, 

 were palTed in the reigns of Edward III., Henry VII., 

 and Elizabeth. The mines having been much negledled 

 during the reign of Mary, Elizabeth invited German miners 

 into the country, and great encouragement was given to 

 mining operations in Cornwall, and various parts of England. 

 The quantity of tin procured annually in the fucceeding 

 reigns of James I. and Charles, amounted to fixtcen hundred 

 tons. During, and for fome time after the civil wars, the 

 tin-trade declined, but revived again in the reign of 

 George I., and has fince been increafing. For an account 

 of the annual produfts of the tin-mines of Cornwall and 

 Devonfhire, fee the article Mine. 

 .AH the tranfatlions connefted with the tin-mines are 

 Bnder the controul of the ftannary laws : courts are held 

 every fix months, and they decide by juries of fix perfons, 

 with a progreffive appeal to the lord warden and lords of 

 the duke of Cornwall's council. By whatever method or 

 accident a vein is difcovercd, permiffion of the proprietor 

 muft be obtained before any operations can be commenced, 

 except in the cafe of fuch tin-mines as are anciently em- 

 bounded according to the provifion of the ftannary laws. 

 (See Stannary Courts.) The owner of the foil is 

 technically called the lord, whofe {hare (which is called 

 his dyj}) is generally one-fixth or one-eighth of the ore. 

 The duke of Cornwall receives a duty of four (hillings 

 per hundred weight of tin, which is taken when the tin 

 IS affayed and licenfed : this procefs is called the coinage, 

 from the French word coin, a corner, A corner is chipped 

 off each block at the ofGce, and if it be found fuffi- 

 ciently pure, the blocks are ftamped with the arms of 

 the duke. The annual revenue of the tin is about 

 10,000/.; the average annual amount being about 3200 

 I tons, and the value about 120/. per ton. The mode 

 of aflay is obvioufly rude and imperfeft ; and we have 

 I heard that foreigners have recently complained that the 

 Britifii tin was not fo pure as that obtained from the 

 Eaft. But whatever be the purity of Britifh tin, there 

 ■ can be no doubt that it is greatly adulterated on the con- 

 t dnent. It is faid that every tin-founder in Holland has 

 I Enghlh ftamps, and be the quahty of the tin what it may, 

 I the infcription makes it pafs for Englifh. The metal with 

 which Britifh tin is adulterated on the continent is lead, 



• which being five times cheaper, and when mixed in fmall 

 quantities not eafily detefted, the temptation for fuch 



Jiraud is great. It is not true, as afferted by fome foreign 



• writers of rafpeftability, that Britifli tin is purpofely 

 jajjpyed with certain portions of copper and lead before it 

 lis exported from Cornwall. The ores of tin, in the tin- 



• mines of Cornwall, are fo intimately alfociated with portions 

 of copper-ore, lead-ore, arfenical pyrites, and oth^r metals, 

 of which a fmall mixture will remain in the block-tin, and 

 can only be feparated by fubiequent refining, that any confi- 

 dcrable portion of alloy may I')e detefted by the increafe of 

 fpccific gravity. Graia-tin, which is the purelt tin of com- 

 merce, is fmeited from the fined ore by a charcoal fire : 

 'he common block- tin is fmeited with pit -coal or culm, as 



before Hated. Grain-tin is ufcd for various piirpofes in tlir 

 arts, where tin of the pureft quality is required. 



Long as the tin-mines of Cornwall have been worked, 

 they ilill continue to fiipply in abundance this ufful metal ; 

 but from the greater extent of the prefent works, and from 

 the circumllance of tin always occupying the upper part of 

 the vein, we may infer that the tin-mines of that county 

 will be exhaufted at no very dillant period. At prefent, 

 the principal part of the tin is obtained from the wellern 

 extremity of the county ; but when the tin-mines in that 

 diftrift are worked out, we may confider the tin-trade of 

 Cornwall as nearly cxtinft. The granitic range of Dart- 

 moor, in Devonfhire, has been lefs explored than Cornwall ; 

 but there is reafon to believe that the metallic repofitories 

 of tin and copper which it contains will furnirti an ample 

 field for the induftry of future adventurers, and a failure in 

 the fupply from Cornwall would greatly enhance tlie price 

 of this metal, and give increafed fpirit to mining fpcculations. 



Tin, in Chemtjlry and the Arts. The colour of tin is 

 white, like that of iilver : it has a fenfible tafte, and when 

 rubbed, emits a peculiar fmell : its hardnefs is greater than 

 that of lead, and lefs than that of xinc : its fpecific gravity 

 is ftatcd by Briffon to be 7.291, and it is faid to become a 

 little greater by hammering : it is very malleable, and may 

 be beaten into very thin leaves. Tin-foil, as it is termed, is 

 ufually about -nrV^th of an inch in thicknefs ; but this is by 

 no means the utmoft degree of thinnefs which it will bear. 

 Its duftility and tenacity are rather low : a tin wire, -^ -^-th 

 of an inch in diameter, is ftated by Mufchenbroeck (as 

 quoted by Dr. Thomfon) to be capable of lupporting a 

 weight of 31 lbs. only, without breaking. Tin may be 

 eafily bent, and when bent, produces a peculiar crackling 

 iioife : it fufes at about 442° of Fahrenheit's fcale, but will 

 bear a moft intenfe heat before it is volatilized. On being 

 expofed to the atmofphere, its furface becomes (lightly tar- 

 niflied, but it undergoes no other change. When kept 

 under cold water it undergoes no change ; but red-hot tin, 

 expofed to the vapour of water, decompofes it, an oxyd 

 of tin is formed, and hydrogen gas is evolved. Expofed to 

 the aftion of the air in a melted ftnte, it quickly becomes 

 covered with a greyifli powder, or oxyd ; and if the heat is 

 very violent, it is ftated to take fire, and to burn with a 

 pale white light. 



Tin unites with oxygen in two proportions, as has been 

 lately proved by Gay Lulfac, in oppofition to Berzelius, who 

 concluded from his experiments that there were three oxyds 

 of tin. (See Annal. de Chimie et Phyf. vol. i. p. 40.) The 

 firft oxyd, or protoxyd, of tin, confifts of about 



Tin 

 Oxygen 



The fecond, or pcroxyd, of about 



100. 

 13.6 



Tin 

 Oxygen 



100. 

 27.2 



This gives the weight of the atom 7-352. Dr. Thomfon is 

 inchned to confider it as 7.375 ; but it perhaps will be 

 found hereafter either 7.25 or 7.5. The firil of thefe 

 oxyds may be formed by difTolving tin in muriatic acid, 

 either by means of heat, or by adding occafionally a little 

 nitric acid : when dilfolved, add to it a folution of potafti ; 

 a white precipitate falls, which is partly taken up again ; 

 but the remainder, on ftanding, alTunies a dark grey colour, 

 and even a metallic luftre ; and on being heated to whitenels, 

 is pure protoxyd of tin. The peroxyd may be formed by 



bailing 



