TIN 



[ 438 ] 



TOR 



siders that the Phoenician colony 

 of Gades, on the western coast of 

 Spain, was the medium or entrepot 

 of the commercial intercourse be- 

 tween Phoenicia and Cornwall. 

 Diodorus says, " we will now give 

 an account of the tin which is 

 produced in Britain." 



Tin occurs in rocks of granite, 

 gneiss, &c., in veins or fissures, 

 called lodes ; also in horizontal 

 beds termed floors ; and it is also 

 found loosely scattered among 

 pebbles. 



TINSTONE. Oxide of tin; an ore 

 containing tin. Tinstone sometimes 

 yields nearly 80 per cent, of its 

 weight in tin. 



TI'TANITE. The ore or oxide of ti- 

 tanium ; it is nearly a pure oxide, 

 is of a brown colour, and is met 

 with in granite and quartz. 



TITANIUM, (from T/TOI/OS, Gr.) One 

 of the substances commonly known 

 as metals. Titanium was first 

 discovered by the Rev. Mr. Gregor 

 in 1789 ; it is of a dark, copper- 

 red colour, with a strong metallic 

 lustre, which tarnishes by exposure 

 to the atmosphere. Werner gaVe 

 the name of Menak to titanium, 

 from the circumstance of its having 

 been first found at Menachan, in 

 Cornwall. 



TOAD-STONE. A provincial term for 

 a species of wack, or basaltick rock, 

 found in Derbyshire. Toad-stone 

 is a pyrogenous or volcanic pro- 

 duction that has been erupted in a 

 fluid state. Its ordinary colours 

 are brownish grey, purplish brown, 

 bluish, or greenish; and its vesicles 

 are either empty, or filled with 

 carbonate of lime. Toadstone is 

 found abundantly in Derbyshire, 

 lying between beds of limestone ; 

 in some instances, beds of toadstone 

 and limestone are found alternating 

 with each other. 



TONGUE- SHAPED. In botany, applied 

 to leaves of an oblong, blunt, thick 

 form, being generally of a cartila- 



ginous substance at the edges. 



TO'PAZ. (from TOTTCL^IOV, Gr. topaz, 

 Fr.) A precious stone or gem, 

 generally of a yellow colour. It 

 is the silice fluatee alumineuse 

 of Haiiy ; the topaze of Brongniart 

 and Brochant. It is harder than 

 quartz, hardness = 8, with a 

 specific gravity of from 3*4 to 3'6. 

 Is massive, in rounded pieces, and 

 crystallised ; most frequently crys- 

 tallised. According to Haiiy the 

 primitive form of topaz is a rec- 

 tangular octahedron. Mr. Allan 

 says " its structure is lamellar at 

 right angles to the axis of the 

 prism ; it also cleaves, though 

 with difficulty, parallel to the 

 sides of a right rhombic prism of 

 about 124 22' and 55 38'; and 

 it appears to yield to mechanical 

 division on all the angles of the 

 prism. There are many varieties 

 of topaz, differing greatly in form 

 and colour. The highly crystal- 

 lised and transparent varieties are 

 named precious topaz. In some 

 places, as in Scotland, the topaz is 

 found in alluvial earths. The 

 Scotch pebble, called cairn-gorum, 

 is a topaz. Generally, the topaz 

 occurs in primary rocks, the finest 

 specimens being obtained from the 

 mountains of Brazil, and from the 

 Uralian mountains of Asiatic Russia. 

 Other minerals are sometimes sold 

 for topaz, but it may generally 

 be distinguished by the rhombo- 

 hedron base of its crystals, straight 

 foliated cross fracture, and longitu- 

 dinally streaked lateral planes. The 

 precious topaz consists of alumina, 

 silica, and fluoric acid, with, some- 

 times, a small quantity of iron. 



TOPA'ZOLITE. A pale yellow, nearly 

 transparent, sub-variety of garnet, 

 found in Piedmont. Its constitu- 

 ents are, silex 37, alumine 2, linffc 

 29, glucine 4, iron 25, manganese 

 2. 



TOR. A small round hill; called 

 also Cam, or Kara. 



