TEL 



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T E M 



terior extremity of the beak. Professor 

 Buckland. 



TKLLI'NA. (tellina, Lat. a limpin.) A 

 genus of orbicular or ovate transverse 

 equivalved, marine bivalves, with a fold 

 on the anterior part, and short beaks, 

 found in sands, at depths varying to 

 fifteen fathoms. Hinge with usually three 

 teeth, the lateral ones smooth on one 

 side. The shells of this genus are chiefly 

 known by the inflection, or irregular fold, 

 on the fore part ; in the one valve the 

 fold is convex, in the other, concave. 

 There are three families of tellinse : ovate 

 and thickish, ovate and compressed, sub- 

 orbicular. Some conchologists have di- 

 vided tellina into three genera ; Tellina, 

 Cyclas, and Pandora. Ninety-four spe- 

 cies are described in Turton's Linne, 

 twenty-two of which have been found in 

 the seas of our coasts. The tellina is 

 remarkable for the quickness and agility 

 with which it can spring to considerable 

 distances, by first folding the foot into a 

 small compass, and theu suddenly ex- 

 tending it ; while the shell is at the same 

 time closed with a loud snap. 



Many species of this genus are found 

 fossil ; Lamarck enumerates ten, as hav- 

 ing been found in the neighbourhood of 

 Paris. Dr. Man tell gives three species 

 as occurring in Sussex ; two in the lower 

 green sand, Tellina sequalis and Tellina 

 inaequalis, and one in the alluvial depo- 

 sites, Tellina solidula. 



TELLI'NIDES. A genus of sub-equivalve, 

 inequilateral, transverse, marine bivalves, 

 found in sandy mud at depths varying 

 from five to fifteen fathoms. 



TE'LLINITE. A fossil tellina. See Tellina. 



TELLU'RIUM. The name given by Klap- 

 roth to a metal first discovered by him or 

 by Miiller in 1782, from an ore of gold, 

 with which metal it is found combined 

 in the Transylvanian mines. Its colour 

 is nearly a tin white, with a shade of 

 blue. Structure foliated. Specific gra- 

 vity 6-1. Before the blow- pipe it fuses 

 easily, and is very volatile, giving out a 

 pungent odour, compared by some to that 

 of a radish. Tellurium is not used in 

 any form. 



NA'TIVE TELLD'RIUM. Rhombohedral Tel- 

 lurium. The tellure natif auro-ferrifere 

 of Hau'y ; gediegen silvan of Werner ; 

 tellure natif ferrifere of Brongniart. This 

 ore is never perfectly pure. It always 

 contains a greater or less quantity of gold, 

 and sometimes silver, lead, copper, and 

 sulphur. It is found in Transylvania 

 only, in veins, traversing greywacke. It 

 is of a white colour ; of a shining and me- 

 tallic lustre ; brittle and frangible. Its 

 constituents are tellurium 92'6, iron 7-2, 

 gold 0-2. 



TE'MPERATURE. (temperatura, Lat. tem- 

 ptrature, Fr. tempra, It.) Constitution of 

 nature ; the constitution or state of the at- 

 mosphere, whether it be hot or cold, humid 



or dry ; the condition of a body, as mani- 

 fested by its influence on the thermometer. 

 A question of great importance, in the 

 study of geology, arises as regards the 

 existing and the former temperature of 

 this planet. Whether the nebular hypo- 

 thesis be correct, (and assuredly, if we 

 dispassionately examine the question with 

 our minds divested of prejudices and pre- 

 conceived notions, there are many very 

 powerful arguments in its favour,) or 

 otherwise, it certainly does appear 

 that a very high temperature did once 

 exist on this planet ; and that such tem- 

 perature has been gradually diminishing. 

 Whether also the nucleus of the globe be 

 in a state of incandescence or fusion is a 

 question which probably never will be 

 solved, till the heavens shall be rolled 

 away as a curtain, and the elements shall 

 melt with fervent heat. Still we well 

 know that the temperature of the earth 

 does increase in a fixed and certain ratio 

 as we descend into its depths. The fol- 

 lowing observations on this interesting 

 subject are extracted from some of our 

 most able geologists and greatest autho- 

 rities. There is so much grandeur and 

 simplicity in the idea of the condensation 

 of gaseous matter into those spheres and 

 spheroids which exist, not only in our 

 solar system, but also by myriads through- 

 out the universe, that we are irresistibly 

 led to adopt some view of this kind, more 

 particularly as it would accord with the 

 unity of design so evident throughout 

 creation. There is no argument, a priori, 

 against the hypothesis that the matter 

 composing our globe may once have 

 existed in a gaseous state, and in that 

 state have revolved round the sun. If it 

 be highly probable that heat to a certain 

 extent resists the action of gravitation in 

 the sun, Jupiter, and Saturn, there is 

 nothing unphilosophical in the inference 

 that heat has resisted, and may continue 

 to resist, in a minor degree, the action of 

 gravitation in our planet. The following 

 are general results from the various facts 

 observable on the earth's surface, and 

 such depths thereof as man has hitherto 

 been able to penetrate. 1. Numerous 

 experiments in mines show an increase of 

 temperature from the surface downwards, 

 that is, from those depths where the 

 action of the solar rays ceases to produce 

 a Variable heat. 2. Thermal springs 

 occur in all parts of the world, and among 

 all varieties of rock. 3. The temperature 

 of the water in Artesian wells is found to 

 increase with the depth. 4. Terrestrial 



