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TBA'VEETIN. (Lapis Tilurtinm, Lat. 

 travertino, It.) An Italian name 

 for a concretionary limestone or 

 calcareous precipitate, deposited by 

 water holding in solution a consid- 

 erable quantity of carbonate of lime. 

 The water parting with some of its 

 carbonic acid gas, which rises in 

 bubbles to the surface, the lime be- 

 comes deposited. Thermal springs, 

 in volcanic districts, are found to 

 issue from the earth, so highly 

 charged with carbonate of lime, as 

 to overspread large tracts of country 

 with beds of calcareous tufa, or 

 travertin. Deposits of travertin 

 are by no means uncommon from 

 cold springs in the Apennines, par- 

 ticularly near the volcanic region 

 of Southern Italy. In Italy, im- 

 mense masses of travertin are being 

 constantly formed from waters 

 copiously charged with carbonate 

 of lime. At the baths of San 

 Fillippo a manufactory of medal- 

 lions in lasso-relievo is carried on. 

 The water is first conducted into 

 pits, where it frees itself from its 

 grosser parts ; it is then conducted 

 by a tube to the top of a small 

 chamber, and made to fall through 

 a space of ten or twelve feet in 

 height. The stream is broken in 

 its descent by means of numerous 

 sticks placed across, by which the 

 spray is dispersed upon moulds, 

 which are slightly soaped, and the 

 result is a cast of the figures formed 

 in the mould, of a solid, marble- 

 like substance. The waters of the 

 lake of the Solfatara, between Eome 

 and Tivoli, are so supersaturated 

 with carbonic acid gas, that they 

 appear in a constant state of ebul- 

 lition, from the extrication of the 

 gas. The Coliseum, and the ma- 

 jority of the public buildings of 

 Home, are composed of travertin. 

 The usual explanation of the depo- 

 sition of travertin seems very pro- 

 bable. It supposes the carbonic 

 acid to be derived from the volcanic 



regions beneath, which, passing 

 with the water through the calca- 

 reous strata, dissolves as much lime 

 as it can take up, giving off the 

 excess of carbonic acid under di- 

 minished pressure in the atmos- 

 phere, and causing the carbonate 

 of lime to be deposited. The car- 

 bonic acid found so abundantly in 

 acidulous springs is ascribed by 

 Von Buch, Brongniart, Boue, Von 

 Hoff, and other geologists, to vol- 

 canic or igneous action at various 

 depths beneath the surface. Masses 

 of travertin are very abundant in 

 districts which have been, or still 

 are, subjected to volcanic action; 

 they are, however, almost equally 

 abundant in countries where there 

 are no distinct appearances of vol- 

 canic action near the surface. All 

 that seems necessary for their pro- 

 duction is, that a spring, should 

 hold in solution a sufficient quan- 

 tity of carbonate of lime, which, 

 upon the escape of the excess of 

 carbonic acid gas into the atmos- 

 phere, deposits its earthy residuum 

 on any object over which it flows. 

 TBE'MOLITE. (from Tremola, a valley 

 of St. Gothard, where it was first 

 found.) A nearly white, grey, or 

 bluish, variety of hornblende or 

 hemiprismatic augite. It occurs 

 in crystals, but most commonly in 

 fibrous or radiated masses, composed 

 of minute, imperfect prisms or fibres. 

 There are several sub-varieties of 

 tremolite, namely, common tremo- 

 lite, glassy tremolite, fibrous tremo- 

 lite, and Baikalite. Tremolite is 

 found almost exclusively in primary 

 rocks, but it sometimes occurs in 

 secondary. Specific gravity from 

 2-9 to 3-2. Hardness from 5'0 to 

 6-0. Before the blow-pipe, tremo- 

 lite fuses into a white glass, full of 

 pores. Its consituents are silex, 

 lime, magnesia, water and carbonic 

 acid, and oxide of iron. Very dif- 

 fering analyses are, however, given 

 by different chemists and mineralo- 



