TROMPE, THE 



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TRAVERTIN. A white concretionary limestone deposited from springs holding 

 carbonate of lime in solution. Travertin is compact ; tufa is a porous body. 



TREACIiE is the viscid brown uncrystallisable syrup which drains from the sugar- 

 refining moulds. Its spec. grav. is generally 1'4, and it contains upon an average 75 

 per cent, of solid matter. See SUGAR. 



TREFOIL, BITTER. One of the clovers which possesses a bitter taste. 



TRENT SAND or WHARPE. A river sand found in some parts of the Trent, 

 and also in the Severn, and some other places ; used for polishing German silver. 



TRIPOLI ( Terre pourrie, Fr. ; Tripel, Ger.) is a mineral of an earthy fracture, a 

 yellowish-grey or white colour, composition impalpably fine, meagre to the touch, 

 does not adhere to the tongue, and burns white. 



M. Ehrenberg has shown that those friable homogeneous rocks, which consist 

 almost entirely of silica, are actually composed of the exuviae or rather the skeletons 

 of Infusoria (animalcules'), of the family of Barccllariee, and the genera Cocconema, 

 Gonphonema, &c. They are recognised with such distinctness in the microscope, that 

 their analogies with living species may be readily traced, and in many cases there is 

 no appreciable difference between the living and the fossil forms. The species are dis- 

 tinguished by the number of partitions or transverse lines upon their bodies. The 

 length is about 5 ggth of a line. M. Ehrenberg made his observations upon the tripolis 

 of Billen in Bohemia, of Santafiora in Tuscany, of the Isle of France, and of Francisbad, 

 near Eger. 



Tripoli is said by Brooke and Miller to be found near Prague in Saxony, in France, 

 Tripoli, Corfu. Tripoli has been confounded by many writers with the English 

 Eottenstone. Mr. Kirwan, in his ' Elements of Mineralogy,' says, ' Mr. Haase who 

 has lately analysed it found 100 parts of it to contain 90 of silicious earth, 7 of argill, 

 and 3 of iron ; but the red sort probably contains more iron.' 



TROXVXPE, THE. The trompe, or water-blowing engine, figs. 2019, 2020, 2021, 

 is employed in some of the great metallurgical works of the Continent. Fig. 2019 is 



the elevation ; fig. 2020 is a vertical section, made at right angles to the elevation. 

 The machine is formed of two cylindrical pipes ; the bodies of the trompe, b b, set up- 

 VOL. III. S 17 



