624 



TIN TINDAL. 



combined by fusion. This alloy is often the prin- 

 cipal ingredient in the compound called pewter. 

 Lead and tin may be combined in any proportion 

 by fusion. This alloy i harder, and possesses 

 much more tenacity than tin ; and these qualities 

 are at a maximum when the alloy is composed of 

 three parts of tin and one of lead. The presence 

 of tin seems to prevent, in a great measure, the 

 noxious qualities of the lead from becoming sensi- 

 ble when food is dressed in vessels of this mixture. 

 This result is often employed to tin copper vessels ; 

 and the noxious nature of lead having raised a sus- 

 picion that such vessels, when employed to dress 

 acid food, might prove injurious to the health, Mr 

 Proust was employed by the Spanish government 

 to examine the subject. The result of his experi- 

 ments was, that vinegar and lemon-juice, when 

 boiled long in such vessels, dissolve a small portion 

 of tin, but no lead, the presence of the former 

 metal uniformly preventing the latter from being 

 iii-tcd on. The vessels, of course, are innocept. 

 What is called ley pewter is often scarcely any 

 thing else than this alloy. Tin foil, too,. i?> almost 

 always a compound of tin and lead. It is in the 

 formation of these alloys that tin is principally em- 

 ployed. Its oxides are used in epatnelling, and to 

 polish the metals ; and its solution in nitro-muriatic 

 acid is an important mordant in the art of dyeing, 

 rendering several colours, particularly scarlet, more 

 brilliant and permanent. 



Tin Ores. These are but two in number, tin 

 ore and tin pyrites. The first of these occurs crys- 

 tallized, and in a great variety of forms, but which 

 may all be derived from an octahedron with a square 

 base, the angle over the apex being 1 12 10'. The 

 majority of the crystals have the general figure of 

 a right square prism, with four-sided pyramids at 

 each extremity. The cleavages take place parallel 

 with the sides of this prism, and with both its dia- 

 gonals. The crystals may be cleaved also parallel 

 to the sides of the above-named octahedron, but 

 with difficulty. The prisms are sometimes verti- 

 cally streaked. Lustre adamantine ; colour various 

 shades of white, gray, yellow, red, brown and black ; 

 streak pale gray ; in some varieties it is pale brown ; 

 semi-transparent, sometimes almost transparent, and 

 at others opaque; brittle; hardness about that of 

 feldspar ; specific gravity 6-96. Tin ore presents 

 itself in a great variety of compound or macled 

 crystals. It also occurs reniform, rarely in botry- 

 oidal shapes, and massive, with a granular or co- 

 lumnar composition, the individuals being strongly 

 connected, and the fracture uneven. The wood tin 

 of the Cornish mines is a mere variety of tin ore. 

 The following ingredients were found in a speci- 

 men of crystallized, and in a massive tin ore : 



Oxide of tin, 

 Oxide of iron, 

 Silex, 



Crystallized. Missive. 



99-00 95-00 



. 0-25 5-00 



0-75 0-00 



In its greatest purity, it contains nothing but oxide 

 of tin. Alone, it does not melt before the blow- 

 pipe, but is reducible when in contact with char- 

 coal. It occurs disseminated through granite, also 

 in beds and veins. It also occurs in pebbles, and 

 is extracted in this shape from stream-works. The 

 variety called wood tin has hitherto been found only 

 in these repositories. There are but few countries 

 in which the present species is met with in consi- 

 derable quantities. These are Saxony, Bohemia, 

 Cornwall, in Europe, and the peninsula of Malacca, 

 and the island of Banca, in Asia. Within a few 



years, small crystals have been met with at Gosben, 

 in Massachusetts, in a granite rock, accompitnicd 

 by tourmaline and spodumenc. Tin pyrites, Hie 

 other ore of tin, occurs massive, with a granular 

 composition; fracture uneven, imperfectly conchoi- 

 dal ; lustre metallic ; colour steel-gray, inclining to 

 yellow; streak black; opaque; brittle; hardness 

 about that of fluor; specific gravity 4-35. Before 

 the blow-pipe, sulphur is driven off, and the mineral 

 melts into a blackish scoria, without yielding a 

 metallic button. It is soluble in nitro-muriuti<- 

 acid, during which the sulphur ia precipitated. It 

 consists of 



Tin, . 

 Copper, 



I run, . 

 Milplmr, 



34-00 



3C-00 



2-00 



25-00 



It is found only at St Agnes, in Cornwall. 



TINCAL. See JBoracic Acid. 



TINCTURE; a solution of any substance in 

 spirit of wine. Rectified spirit of wine is the 

 direct menstruum of the resins, and essential oils 

 of vegetables, and totally extracts these active 

 principles from sundry vegetable matters, which 

 yield them to water not at all, or only in part. It 

 dissolves, likewise, the sweet, saccharine matter of 

 vegetables, and generally those parts of animal 

 bodies in which their peculiar smell and taste re- 

 side. The virtues of many vegetables are extracted 

 almost equally by water and rectified spirit ; but 

 in the watery and spirituous tinctures of them there 

 is this difference, that the active parts in the watery 

 extractions are blended with a large proportion of 

 inert gummy matter, on which their solubility in 

 this menstruum in a great measure depends, while 

 rectified spirit extracts them almost pure from 

 gum. Hence, when the spirituous tinctures are 

 mixed with watery liquors, a part of what the 

 spirit had taken up from the subject generally sepa- 

 rates and subsides, on account of its having been 

 freed from that matter, which, being blended with 

 it in the original vegetable, made it soluble in 

 water. This, however, is not universal, for the 

 active parts of some vegetables, when extracted 

 by rectified spirits, are not precipitated by water, 

 being almost equally soluble in both menstrua. 



TINDAL, MATTHEW, LL.D., a controversial 

 writer, born about 1657, in Devonshire, where his 

 father was a clergyman, was admitted of Lincoln 

 college, Oxford, in 1672, elected a fellow of All 

 Souls' college, and afterwards became a doctor of 

 law. At the commencement of the reign of James 

 II., he turned Roman Catholic, but, in 1687, he re- 

 turned to the church of England. Having con- 

 curred in the revolution, he was admitted an advo- 

 cate, and sat as a judge in the court of delegates. 

 He published several pieces, political and theologi- 

 cal, among which were a Letter to the Clergymen 

 of the two Universities, on the subject of the 

 Trinity and Athanasian creed, and a treatise entitled 

 the Rights of the Christian Church. This work 

 excited a considerable sensation among the high 

 church clergy, who attacked it with great animosity. 

 Tindal published a defence, the second edition of 

 which the house of commons ordered to be burned 

 by the common hangman, in the same fire with 

 Sacheverel's sermon, thus treating the disputants 

 on each side in the same manner. In 1730, he 

 published his Christianity as old as the Creation, or 

 the Gospel a Republication of the Religion of Na- 

 ture, in which his object was to show that there 

 neither has been, nor can be, any revelation distinct 



