T R O 



T R O 



ijcrUx of the trochoid ; and the plane comprehended between 

 the trochoid and its bafe, the trochoidal fpace. 



The trochoid is the fame with what we otherwife call 

 the cycloid ; for the properties, &c. of whicli, fee Cycloid. 



TROCHOIDES Lacus, or Trachoide Lake, in Ancient 



Geography, a lake in the ifle of Delos. It was on the bor- 



TROCHMI, in Ancient Geography, the name of one of ders of this lake, that, according to the mythologifts, La- 



toaa was brought to bed of Apollo and Diana; and here 

 the firft of thefe deities had a temple. 



TROCHTELFINGEN, in Geography, a town of 



TROCHLEA, r^oj/n^ia, one of the mechanical pcfwers, 

 ufually called a/a&j'j which fee. 



Trochlea, in Anatomy, a name given to feme articular 

 emanations of bones, which refemble in form the groove of 

 a pulley : w'z. that of the humerus, adapted to the ulna. 



TROCHLEARIS, a mufcle of the eye. See Eye. 



the three Gaulifh nations, which, according to Strabo 



eflablifhed themfelves in that part of Galatia which refpefts 



■ the Euxine fea, and that which touches on Cappadocia. 



TROCHOCARPA, in Botany, from Tpo;^oc, a ivheel, 



and xstpirsc, fruit, ferving to exprefs the orbicular depreffed 



form of the nut, hke a little toothed wheel Brown Prodr. 



Nov. HoU. v. I. 548 Clafs and order, Pentandria Mono- 



gynia. Nat. Ord. Epacrideie, Brown. 



Gen. Ch. Cal. Perianth inferior, of five equal, ereft, 

 ovate leaves, with two fmaller ones, of the fame fhape, at 

 the bafe, permanent. Cor. of one petal, funnel-fhaped ; 

 tube cyhndrical, pervious, longer than the calyx ; limb in 

 five deep, ovate, fpreading fegments, bearded on the upper 

 fide. Neftary cup-(haped, five-lobed, furrounding the 

 bafe of the germen. Stam. Filaments five, thread-lhaped, 

 the length of the tube, inferted into its lower part ; anthers 

 oblong, incumbent, included within the tube. Pifl. Ger- 

 men iuperior, ovate ; ftyle very fhort ; (ligma fimple. 

 Perk. Drupa globofe, depreffed, juicy. Seed. Nut orbi- 

 cular, with ten lobes, finally feparating into as many dif- 

 tinft cells, with a kernel in each. 



Eff. Ch. Outer calyx of two fcales. Corolla funnel- 

 (haped, with a pervious naked tube, and a five-cleft, fpread- 

 ing, bearded limb. Stamens within the tube. Drupa 

 pulpy. Nut wheel-{haped, ten-lobed, ten-celled. 



1. T. laurtna. Laurel -leaved Trochocarpa. Br. n. i. 

 (Cyathodes laurina ; Rudge Tr. of Linn. Soc. v. 8. 293. 

 t. 9.) — Found near Port Jackfon, New South Wales. A 

 fmall tree, fmooth in every part, with very hard wood. 

 Leaves fcattered, on fhort ftalks, elliptic -lanceolate, acute, 

 entire, many-ribbed, with fomewhat of the afpedl of a 

 Rufcus, each near two inches long. Spikes rather lax, ter- 

 minal and axillar)-, fhorter than the leaves. Floiueri white, 

 fmall. Fruit lefs than a pea. 



TROCHOID, Trochois, or Trochoides, formed from 

 Tpop^of, ivheel, and eiooj-, form, in Geometry, a curve, whofe 

 genefis may be thus conceived : if a wheel or circle be 

 moved with a two-fold motion at the fame time, the one 

 in the right line, and the other circularly about its centre, 

 and thefe two motions be equal, i. e. defcribe two equal 

 lines in the fame time : and if in the radius, which at the 

 beginning of the motion reaches from the centre of the 

 wheel, or the firft point of the line which defcribes the 

 circumference : if, I fay, in this radius, a point be taken 

 any where, except in the centre, this point will defcribe a 

 curve, one part of which will be below the line defcribed 

 by the centre, and the other above it. This hne, thus de- 

 fcribed by the point taken in the radius, is called the 

 trochoid. 



The right line which joins the two extremities of the 

 trochoid, and which is either the path the wheel makes, 

 or a line parallel to that path, is called the bafis of the 

 trochoid. 



The axis of the trochoid is the diameter of the wheel, 

 perpendicular to the bafe in the middle of the motion ; or 

 that part of the radius between the trochoid and its bafe. 

 The point, in which the axis is cut into two parts by the 

 line defcribed by the centre of the wheel, is called the cen- 

 tre of the trochoid ; the uppermoft point of the axis the 



in Ueography, a town 

 Wurtemberg, lately imperial; 16 miles N.W. of Buchau. 

 N. lat. 48° 16'. E. long. 9° 18'.— Alio, a town of Ger- 

 many, in the county of Oettingen, on the Eger ; 4 miles 

 S.W. of Nordlingen. 



TROCHUS, in Antiquity, denotes the exercife or game 

 of the hoop. The hoop was of iron, five or fix feet in 

 diameter, fet on the infide with a number of iron rings. 

 The boys and young men ufed to whirl this along, as our 

 children do their hoops, direfting it with a rod of iron, hav- 

 ing a wooden handle : which rod the Grecians called s?.«1i:f,. 

 and the Romans radius. The clattering of the ring ferved 

 partly to the diveriion, and partly as a notice for perfons to 

 keep out of the way. Horace de Art. Poet, ranks this, 

 exercife among other manly fports : 



" Ludere qui nefcit, campeftribus abftinet armis, 

 Indoftufve, pilse, difcive, trochive quiefcit." 



Trochus, in Natural Hiflory, the name given by authors 

 to a genus of fhelh ; fome of the fpecies of which refemble 

 the figure of the trochus, or top, which boys play with. 

 As there are many fpecies of this fhell, however, which are 

 flatted and have nothing of this form, the whole feries of 

 them are much better named, by a denomination taken from 

 the fhape of the mouth, which is of an oval figure, and is 

 alike in all thefe fpecies, and different from all other (hells. 

 They are therefore aptly charafterifed by a late French 

 writer under the name of cochlea ore deprejfo- 



The trochi, or tops, form the fifteenth family of (hells 

 in Da Cofta's arrangement ; and he defines them to be (hells 

 of a conic or pyramidal (hape, the top being broad and 

 flattifh, and gradually tapering thence to a very Iharp point ; 

 the aperture or mouth is moft generally angular, low, and 

 narrow. This is a numerous family, and abounds with 

 curious and fine (hells. See Trochus, under Conchology. 



There is a foflile fpecies of trochus, not yet difcovered 

 recent. It is a large kind, flattifh, and like a cochlea hehx, 

 generally about two inches in diameter, much wTinkled, 

 with (harp prominent edges hke plates, which are fpiked at 

 regular diftances, running acrofs the fpires; and the whole 

 (hell is likewife ftriated. This trochus is found in the lime- 

 done of Coalbrook-dale in Shropfhire, and Dudley in 

 Stafford (hire. 



TROCKENBERG, in Geography, a to\vn of the 

 duchy of Stiria ; 4 miles N.N.W. of Rein. 



TROCTOU, a fmall ifiand in the Eaft Indian fea, sear 

 the coaft of Qupda. N. lat. 6^ 30'. E. long. 99° 33'. 



TROCTUS, in Ichthyology, a name given by Ariftotle, 

 jEUan, Athenasus, and others of the Greek writers, to the 

 fi(h called amia by Phny, and moft other of the later, as 

 well as ancient Latin writers ; but by fome, lechia and 

 glaucus. It is properly a fpecies of the fcomber ; which 

 fee. 



TROCZENIECZ, in Geography, a town of Poland, 

 in the palatinate of Braclaw ; 20 miles S. of Braclaw. 



TRODEN, a town of Germany, in the principality of 

 Querfurt ; 8 miles S.E. of Juterbock. 



TRODENA, 



' I 



