T I N 



[ 2CO ] 



T O U 



100 feet, it seldom or never happens that 

 tin is found below it in the same vein." 

 There are, however, many instances of 

 tin-ore accompanying copper-ore to great 

 depths. 



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 contain- 

 ing tin. Tinstone sometimes yields nearly 

 80 per cent, of its weight in tin. 



TITANI'FEROUS. (from titan or titanium, 

 and fero, Lat. to produce.) Yielding 

 titanium ; containing titanium. 



TI'TANITE. The ore or oxide of titanium ; 

 it is nearly a pure oxide ; is of a brown co- 

 lour, and is met with in granite and quartz. 



TITA'NIUM. (from riravoc, Gr.) One of 

 the substances commonly known as me- 

 tals, forming one of the fifty-five simple or 

 elementary bodies. 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 tar- 

 nishes by exposure to the atmosphere. 

 Werner gave the name of Menak to tita- 

 nium, from the circumstance of its having 

 been first found at Menachan, in Cornwall. 



TOAD-STONE. A provincial term for a spe- 

 cies of wack, or basal tick rock, found in 

 Derbyshire. Mr. Phillips asks whether 

 this word is derived from the German 

 todstein, in which case it would signify, 

 in mining language, a rock unproductive 

 of mineral treasures, a character generally 

 applicable to toadstone. It appears, how- 

 ever, that writers on mineralogy generally 

 state the name to be given to toadstone 

 from a supposed resemblance in its general 

 aspect to the exterior of a toad. Toad- 

 stone is a pyrogenous or volcanic produc- 

 tion 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 in- 

 stances, 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 cartilaginous sub- 

 stance at the edges. 



TOOTHED. See Dentate. 



TO'PAZ. (from ro7ratov, 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, with a specific gravity of 

 from 3'4 to 3-6. There are many varie- 

 ties of topaz, differing greatly in form 



and colour. The highly crystallized 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. The precious topaz con- 

 sists of alumina, silica, and fluoric acid, 

 with, sometimes, a small quantity of iron. 



TOPA'ZOLITE. A pale yellow, nearly trans- 

 parent, subvariety of garnet, found in 

 Piedmont. Its constituents are, silex 

 37, alumine 2, lime 29, glucine 4, iron 25, 

 manganese 2. 



TORNATE'LLA. A genus of oval, spirally 

 grooved, marine, univalves, belonging to 

 the family Plicacea. Recent tornatellse 

 are found in shallow water, creeping on 

 sands, and leaving furrows. Several spe- 

 cies are found in the oolite and super- 

 jacent strata. 



TORO'SE. ^ (torosus, Lat.) Swelling into 



TO'ROUS. $ knobs or protuberances. A 

 term used both in botany and conchology. 



TORPE'DO. (torpedo, Lat. from torpeo, to 

 benumb.) A subgenus of fishes, be- 

 longing to the genus Raia. The torpedo 

 is found fossil in the tertiary formations. 

 The torpedo is furnished with an elec- 

 trical apparatus, resembling the voltaic 

 battery, which it has the power of charg- 

 ing and discharging at pleasure. The 

 benumbing effect producible by the tor- 

 pedo depends on certain singularly con- 

 structed organs composed of membranous 

 columns, filled from end to end with la- 

 minae, separated from each other by a fluid. 



TO'RRELITE. A new mineral brought from 

 the United States, and thus named after 

 Dr. Torrey. 



TO'RTOISE. (tortue, Fr.) An order of the 

 class Reptilia, or reptiles ; tortoises are 

 also termed Chelonians. The chelonians, 

 or tortoises, were all included by Lin- 

 meus in one genus, namely, testudo ; they 

 are now divided into five subgenera. 

 1. Testudo, or land- tortoise ; 2. Emys, 

 or fresh-water tortoise ; 3. Chelonia, or 

 sea- tortoise ; 4. Chelys ; 5. Trionyx, or 

 the tortoise with a soft shell. 



This order of reptiles, geologists inform 

 us, began to exist at about the same 

 period with the order of Saurians, and 

 has continued from that time to the pre- 

 sent. No fossil remains of the tortoise 

 have been discovered in any strata not 

 more recent than the coal formations. 



TOU'RMALINE. } A mineral which has been 



TOU'RMALIN. $ divided by some miner- 

 alogists into two sub-species, namely, 

 schorl and tourmaline ; by others, tourma- 

 line is regarded as a sub-species, or va- 



