TRA 



TRA 



means of which the culminations of ce- 

 lestial objects are observed. It consists 

 of a telescope firmly fastened on a hori- 

 zontal axis directed to the east and west 

 points of the horizon, or at right angles 

 to the plane of the meridian of the place 

 of observation. 



TRANSITION SERIES. Submedial 

 rocks. A geological designation of the 

 upper metamorphic rocks, which form a 

 kind of link between the primary and 

 the secondary rocks, partaking of the 

 characters of both. They are divided 

 into two series or systems, the Greywacke 

 and the Silurian. 



TRANSLATION. This word is used 

 in Mechanics, as distinguished from Ro- 

 tation, in the following manner: — A 

 body has motion of translation when all 

 its points move in parallel straight 

 lines ; when, in fact, all its points have 

 the same motion. If all have not the 

 same motion, there is either simple 

 rotation, that is, about one permanent 

 axis ; or rotation about a varying axis ; 

 or else a compound of translation and 

 rotation. The motion of a single point 

 must always be called translation, rota- 

 tion being an inadmissible idea. — Pen. 

 Cycl. 



In Geometry, the word translation has 

 a wider sense; perhaps, transference 

 might be a preferable term, as applied to 

 the motion of a figure from one part of 

 space to another. The case meets us at 

 the fourth proposition of the First Book of 

 Euclid's Elements, in which we have to 

 conceive of one figure being transferred 

 by some means ; for it is impossible to 

 imagine space removed, or any part of 

 space made to change place. — Ibid. 



TRANSLU'CENT and TRANSPA'- 

 RENT. 1. Translucent hodXe^ are those 

 which permit light to pass through them, 

 but not in sufficient quantity to render 

 objects distinct, as to colour, distance, or 

 form, when viewed through them. 2. 

 Transparent bodies are those which per- 

 mit the rays of light to pass freely 

 through them, as air and some of the 

 gases, which transmit light without 

 being visible themselves : glass and 

 water are less transparent. Translucent 

 bodies might be termed semi-transpa- 

 rent. 



TRANSMUTATION. The alchemi- 

 cal operation of changing the imperfect 

 into the perfect metals. In geometry, the 

 changing of one figure into another of 

 equal area or content, as of a triangle 

 into a square, of a sphere into a cube. 

 342 



TRANSPOSITION. In Algebra, the 

 process of removing or transposing a 

 term from one side of an equation to the 

 other, at the same time changing its 

 sign. Thus, the equation, a = h + c 

 becomes, by transposition of c, the equa- 

 tion a—c=b, the value of which is pre- 

 cisely the same as that of the preceding. 

 The process amounts to merely subtract- 

 ing c from both sides of the equation. 



TRANSVE'RSAL. The name given 

 in Mathematics to a line, whether right 

 or curved, which is drawn across or in- 

 tersects a system of other lines, right or 

 curved 



TRANSVERSE. The name frequently 

 given to one of the axes of a figure, 

 usually that of the greater magnitude or 

 which goes across the figure. Thus, the 

 longer axis of an ellipse or of a hyper- 

 bola is the transverse axis ; the equato- 

 rial axis of the globe is the transverse. 

 Properly speaking, the term is merely 

 relative : each axis is transverse to the 

 other. 



TRANSVERSE MAGNET. A pecu- 

 liar variety of bar magnets, whose poles 

 are not at the ends, but at the sides : 

 these magnets have always some even 

 number of polar lines. They are made 

 by thrusting 2, 4, 6, &c. bar magnets 

 through a ring in the direction of its 

 diameter, and with their unlike poles 

 opposite to each other; a suflBcient space 

 is left between these magnets to pass the 

 bar between them which it is proposed 

 to magnetise, so that it may touch them 

 as it is drawn through. 



TRAP and TRAPPEAN ROCKS 

 {trappa, Swedish, a stair). Volcanic rocks 

 composed of felspar, augite, and horn- 

 blende. The various proportions and 

 state of aggregation of these simple mi- 

 nerals, and diflTerences in external forms, 

 give rise to varieties, which have received 

 distinct appellations, as Basalt, Amygda- 

 loid, Dolorite, Greenstone, and others. 

 The term is meant to denote that the 

 rocks of this class sometimes occur in 

 large tabular masses, which rise one 

 above another, like steps or stairs. 



Trap conglomerate. The name given 

 to conglomerates formed of fragments 

 of greenstone, basalt, or claystone, to- 

 gether with portions of stratified rocks, 

 more or less rounded by attrition, and 

 imbedded in a paste of the same nature, 

 or having their intervals filled up by it. 

 Such deposits, usually in the form of 

 irregular beds, are named by many geolo- 

 gists trap tufa. A considerable portion 



