TRA 



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pome bodies possess of permitting the pas- 

 sage of rays of light , but without sufficient 

 transparency to perceive the definite out- 

 line of objects through them. 



TRANSMOTA'TION, from trans and muto, 

 to change ; change into another nature or 

 substance. The great object of Alchemy 

 was the transmutation of base metals into 

 gold. 



TRAN'SOM, Lat. transenna. 1. A beam 



across a double-lighted window. 2. The 



lintel over a door. 3. A timber extend- 

 ing athwart the stern post of a ship, to 



fortify it and give it form. 1. The vane 



of the instrument called a cross-staff. 



TRANSPOSITION, from trans and position. 

 A changing of the place of things, as, 1. In 

 algebra, the bringing of a term of an equa- 

 tion to the other side. Thus ax + x 

 b = bx d by transposition becomes 

 * + (a 6) x = b d. 2. In gram- 

 mar, a change in the natural order of the 



words of a sentence. 3. In music, a 



change in the composition, either in the 

 transcript or performance, by which the 

 whole is removed into another key 



TRANSCBSTANTIA'TIOJJ, from trans and 

 substance; change of substance. In the 

 Homish theoloyy, the supposed conversion 

 of the bread and wine in the eucharist 

 into the body and blood of Christ. The 

 doctrine of the real presence assumes tha* 

 the body and blood of Christ are really 

 present with the bread and wine. 



TRANSUDA'TION, from tratistido. Passing 

 off through the pores of a substance. This 

 term should be distinguished (in physi- 

 ology), from perspiration, which implies a 

 function by which the perspired fluid is 

 secreted from the blood, whereas by trans- 

 udation a fluid merely oozes through un- 

 altered. 



TRANS'VERSE Axis. In conic sections, the 

 diameter which passes through both foci. 



TR.VNSVEH'SAL. In<7eotnefry,aline which 

 intersects any other lines. 



TRAP. Trap Hocks. A name given by 

 Kirwan, from Sax. trapp, a stair, to ba- 

 saltic rocks, on account of the stair-like 

 appearance which their vertical edges 

 exhibit. All the rocks of the trap-family 

 are of igneous origin, and bear a close 

 analogy, in their nature and composition, 

 to the products of the active volcanoes 

 erupted in our own time, and especially 

 to the beds of old lava. 



TRAP'EZIUM, T%aviiov, a little table. 

 1. In geometry, a quadrilateral figure, 

 whose four sides and angles are unequal, 

 but two of its sides parallel. 2. In an- 

 atomy, a bone of the second row of the 

 carpus, so called from its shape. 



TRAPE'ZIVS. A trapeziform muscle, 

 which serves to move the scapula in dif- 

 ferent directions. It is situated under 

 the intpsuments of the posterior part of 

 Uie cerk aud back. 



TRAP'EZOID, from trapezium and u3n t 

 like. An irregular figure, which has all 

 its four sides and angles unequal, aud 

 none of its sides parallel. 



TRAP'PISTS. A religious order still ex- 

 tant in Normandy. 



TRAP-TUFF. A variety of trap. A con- 

 siderable portion of Arthur's Seat, near 

 Edinburgh, is formed of this rock. 



TRAU'MATE. The name given by the 

 French geologists to Grauwacke. 



TRAUMAT'IC, from T^OU>U., a wound. 

 In surgery, relating to wounds, hence 

 traumatic balsams 



TRAV'ELLER. In navigation, a. description 

 of thimble, whose diameter is much larger 

 in proportion to the breadth of its sur- 

 face than the common ones. The tra- 

 vellers are intended to facilitate the hoist- 

 ing and lowering of the top-gallant-yards 

 at sea. 



TRA'VERSE, from transverse. 1. In geo- 

 metry, the same as transverse. 2. In 



fortification, a trench, with a little para- 

 pet, sometimes two, one on each side, to 

 serve as a cover from the enemy that might 

 come in flank. 3. In architecture, gal- 

 lery of communication in a church, or 

 other large building.^^-4. In law, tra- 

 verse denotes the denial of some matter 

 o f fa^t, alleged to be done in a declaration 

 o pleading; upon which the other side 

 maintaining that it was done, issue js 

 joined, for the cause to proceed to trial. 

 To traverse an indictment, is to deny some 

 chief point of it, and take issue thereon. 

 5. In navigation, traverse sailing im- 

 plies a compound course, in which several 

 different courses and distances are made 

 and known. To find the real course in this 

 case, traverse tables have been calculated, 

 where all the differences and departures 

 are given for any distance in 100 miles. 



TRAVER'TINO. An Italian name for a 

 calcareous tufa, deposited by water hold- 

 ing bicarbonate of lime in solution. In 

 Italy, immense masses of this substance 

 are constantly being formed, and the pro- 

 cess appears to have been in operation 

 since a very early period of the world's 

 physical history. The Coliseum, St. Pe- 

 ter's, and indeed most of the public build- 

 ings of Home, are composed of travertine. 



TRAVES'TIE, Fr. travestir, to disguise. A 

 word synonymous with parody. 



TREA'CLE, Lat. theriaca. The brown 

 viscid syrup which drains from sugar- 

 refining moulds. 



TREAD. In architecture, the horizontal 

 surface of a step. 



TREAD'LE, ) That part of a loom, turn- 



TRED'DLE. / ins-lathe, or other ;\>\:;'.n- 

 gous machine, on which the foot is set W 

 put it in motion. 



TRE.VD'MILL, ) A wheel exactlv simi- 



THEAD'WHEEL. J lar in its priuciw? *o 



3 A 2 



