T O U 



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TR A 



the horizontal coil, and through a circular 

 card placed above it, on which a gradu- 

 ated circle is drawn. It is then attached 

 to the torsion filament, which is fixed to 

 a screw A, supported by the frame of the 

 instrument. The filament may be of 

 glass, and the angle of torsion may be 

 easily measured upon the graduated card. 

 The wires of the coil are to be connected 

 with the plates of the circuit by means 

 of small mercury cups, a b. 



TOR'SO, Fr. torse. A name given by 

 artists to all mutilated statues, of which 

 nothing remains but the trunk. The 

 term is also applied by architects to 

 columns with twisted shafts. 



TORT. In law, a personal injury done 

 to another. 



TOR'TOISE. All tortoises are placed in 

 one genus, Testudo, by Linnaeus, but 

 Brongniart and others have subdivided 

 them, chiefly according to the forms and 

 teguments of their shell, and their feet. 

 The land tortoises form the genus Testudo ; 

 the fresh-water tortoises, the genus Emys ; 

 and the sea tortoises, the genus Chelonia. 

 Merrem has further distinguished by the 

 name of Sphargit those cheloniae whose 

 shell is destitute of plates, and merely 

 covered with a sort of leather. The Tes- 

 tudo Jimbria, Gm., found in Guiana, has 

 been placed in a subgenus, Chelys, by 

 Dumeril; and the soft-shelled tortoises 

 have been arranged in a genus, Trionyx, 

 by Geoffroy. To this belongs the tyrse 

 of Egypt ; and the soft-shelled tortoise, 

 which inhabits the Carolinas, Georgia, 

 the Floridas, and of Guiana, so highly 

 esteemed for its flesh. 



TOR'TOISE-SHELL. The yellowish-brown 

 scales of the Testudo imbricata, Lin., a 

 species of the tortoise, which inhabits 

 tropical seas. It is extensively used in 

 the manufacture of combs, snuff-boxes, 

 &c., and in several kinds of ornamental 

 work. It is worth in the London market 

 from forty to sixty shillings per Ib. 



TOR'TTLOUS, Lat. tortulosus. Bulged 

 outaj intervals, like a cord having several 

 knots on it. Applied in Natural History. 



TO'RUS. In architecture, a large semi- 

 circular moulding, used in the bases of 

 columns, Ac. 



TO'TIES QCO'TIES. So often as a thing 

 shall happen. A legal phrase. 



TOTIPALM A'TJE, from totus, complete, and 

 pnlmatus, palmate. A family of palmi- 

 pede birds, remarkable for having the 

 rhumb united with the toes by one single 

 membrane, a mode of organisation which 

 renders their feet complete like ours. 

 They nevertheless perch on trees. The 

 pelican is an example. 



TOUCH. In MM! affairs, sails are said 

 to touch when the wind comes edgeways 

 %pon them. 



IOCCH-NSE'DLES. Small masses of gold 



silver, and copper, each pure, and In til 

 the different combinations, proportions, 

 and degrees of mixture, prepared for the 

 triai of gold and silver, on the touch- 

 stone, by comparison of the mark they 

 respectively leave on it. 



TOUCH'STONE A variety of extremely 

 compact siliceous schist, almost as close 

 as flint, used for ascertaining the purity 

 of gold and silver by the streak impressed 

 on the stone by the article tried. 



TOUR'M ALINE. A mineral of the gem 

 order, of many varieties, which occurs 

 imbedded in granite, gneiss, mica-slate, 

 &c., in Scotland, Sweden, Spain, France, 

 Siberia, and many parts of America, aa 

 Massachusetts and Brazil. The funda- 

 mental form of the crystal is a rhombo- 

 hedron. Lustre, vitreous ; colour, brown, 

 green, blue, red, white, frequently black, 



fenerally dark, and scarcely ever bright, 

 treak white. Transparent. Hardness 

 7 to 7'5. Sp. gr. 3-1. Constituents, silica, 

 alumina, soda, coloured by oxide of man- 

 ganese when red, and with oxide of iron 

 when black. The green, blue, &c. varie- 

 ties contain usually both these oxides. 

 Plates, particularly of the brown tour- 

 maline, if cut parallel to the axis, absorb 

 one of the polarised pencils of light. The 

 name is a corruption of the Ceylonese 

 name tournamal. 



TOUR'NIQUET, Fr. from tourner, to turn 

 A surgical instrument, used for stopping 

 the flow of blood into a linib, by compres- 

 sion of the main artery. 



Tow. (Sax.) 1. The coarse and broken 

 part of flax or hemp, separated from the 



finer part by the hatchel or swingle. 



2. A rope. 



TOW'INO. Drawing a vessel forward in 

 the water by means of a rope or tow at- 

 tached to another vessel or boat. .Steam- 

 vessels are often employed to tow sailing 

 vessels up rivers, &c. 



ToxicoL'ooY,froniT;*sv,a poison, and 

 Asyo?, a discourse. The study of poisons, 

 a treatise on poisons. 



TOX'OTES. The generic name given by 

 Cuvier to a fish characterised like the 

 Cheetodon rostratus, by spurting water on 

 insects which frequent aquatic plants, to 

 beat them down, and thereby bring them 

 within its reach. 



TRABEA'TION, Lat. trabes, a beam. In 

 architecture, the same as entablature. 



TRAB'ICULE, Lat. trabicula. A little 

 beam. A term applied by anatomists to 

 designate the thread-like processes in the 

 longitudinal sinus of the dura mater. 



TRACHE'A, r^a^ua. 1. The windpipe. 



2. In natural history, the air-tubes of 



plants are by botanists called trachea, and 

 the same term is applied by entomolo- 

 gists to those vessels which receive the 

 arterial fluid, and distribute it to ever/ 

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