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leg of the angle to be meafured, and the centre C over the 

 vertex of the fame. The firft is done, by looking through 

 the fights F and G at the extremities ot the diameter to a 

 mark nxcd up in one extremity of the leg ; the latter is had 

 by letting fall a plummet from the centre of the inftrument. 

 This done, turn the moveable index H I on its centre to- 

 veards the other leg of the angle, till througli the fights 

 fixed in it, you fee a mark in the extremity of the leg. 

 Then the degree, which the index cuts on the limb, is the 

 quantity of the angle. 



For farther ufes of the femicircle, they are the fame with 

 thofe of the theodolite, 



SEMICIRCULAR Arches. See Arch. 



Semicircular Canals, in Anatomy, three fmall mem- 

 branous tubes, inclofed in excavations of the bone, and com- 

 pofing part of the labyi-inth of the ear. See Ear. 



SEMICIRCULARIS T.-ema, a part of the brain. 

 See Brain. 



Semicircularis Palpebrarum Mufculus, a name given 

 by Spigelius, and fome others, to one of the mufcles of the 

 face, called by Albinus and Winflow the mufculus orbi- 

 cularis palpebrarum. 



SEMICOLON, in Grammar, one of the points or Hops, 

 ■jfed to diftinguilh the feveral members of a fentence from 

 each other. 



The mark or charafter of the feraicolon is (;). It has its 

 name, as having fomewhat lefs effeft than a colon, or as de- 

 manding a fhorter paufe. 



The ufe of tlie femicolon, the grammarians generally fay, 

 is to mark a fenfe lefs complete than the colon, and more 

 complete than tlie comma ; but this only conveys a very ob- 

 fcure idea. In effeft, the precife office of the femicolon, or 

 that office which diltinguiflies it from the colon, is a thing 

 very little known to th:- world. Our beil authors leem to 

 ufe them promifcuoufly. See Colon. 



Dr. Ward, formerly profefibr at Grefham, is perhaps the 

 firft who fettled a juft ufe of the femicolon. His pofition 

 is, that the femicolon is properly ufed to diflinguifh the con- 

 junA members of fcntences. Now by a conjunft member 

 of a fentence, he means, fuch an one as contains at leaft two 

 fimple members. 



Whenever, then, a fentence can be divided into feveral 

 members of the fame degree, which are again divifible into 

 other fimple members, the former are to be feparated by a 

 femicolon. 



E. gr. If Fortune bear a great fway over him, who has 

 nicely Hated and concerted every circumftance of an affair ; 

 we mult not commit every thing, without rcferve, to For- 

 tune, lelt file Ihould have too great a hold of us. 



But thoui^h the proper ufe of the femicolon be to diftin- 

 guifh conjundt members, it is not necefi'ary that all the 

 members divided by it be conjunft. For upon dividing a 

 fentence into great and equal parts, if one of them be con- 

 jundt, all thofe other parts of the fame degree arc to be dif- 

 tinguifhed by a femicolon. Thus, whoever is overtaken 

 with poverty ; the fame will find, that coldnefs, contempt, 

 injuries, &c. are not far behind. Hither likewife may be 

 referred fuch fentenccs, where the whole going before, the 

 parts follow: as, the parts of rhetoric are four; invention, 

 difpofition, elocution, and pronunciation. 



According to bifhop Lowth, a member of a fentence, 

 whether fimple or compounded, that requires a greater paule 

 than a comma, yet does not of itfelf make a complete fen- 

 tence, but is followed by fomething clofely depending on it, 

 may be dillinguidied by a femicolon. E. gr. But as this 

 paffion for admiration, when it works according to rcafon, 

 improves the beautiful part of our fpecies in every thing that 



S E M 



is laudable ; fo nothing is more deftruftive to them, when 

 it is governed by vanity and folly. Here the whole fen- 

 tence is divided into two parts by the femicolon ; each of 

 which parts is a compounded member, divided into its fimple 

 members by the comma ; which fee. 



SEMICON, a mufical inilrumciit among the Greeks, 

 which had thirty-five firings. 



SEMICROMA, Sextuple of. See Sextuple. 



SEMI-CUBICAL Parabola, a curve of the fecond 

 order, in which the cubes, of the ordinates are as the fquares 

 of the abfciffes. Its equation is ax"' ^^yK 



SEMICUPIUM, a half bath, in which the patient is 

 only placed up to the navel. See Insessus. 



SEMIDIAMETER, a right iine drawn from the centre 

 of a circle or fphere, to its circumference ; the fame with 

 what we otherwife call a radius. 



The diilauces, diameters, &c. of the heavenly bodies, 

 are ufually cftimated by altronomers in femidiameters of the 

 earth. 



For the proportions and values of the femidiameters of the 

 planets, fee Planets. For their apparent femidiameters, 

 fee Diameter. 



SEMI-DIAPASON, in Mufic, a defeftive oftave ; or 

 an otlave diminifhed by a lefTer iemitone, or four commas. 

 See Diapason. 



SEMI-DIAPENTE, a defedive fifth, called ufuaUy 

 by the Italians falfa quinta, and by us a falfe fifth. 



SEMI-DIATESSARON, a defeftive fourth, called, 

 properly, a falfe fourth. 



SEMI-DITONE, Diapason. See Diapason. 



Semi-ditone, Dts-diapafon. See Dis-diapason. 



SEMI-DITONUS, is ufed by fome writers, as Salinas, 

 for the third minor. 



SEMI-DOUBLE, in the Roml/li Breviary, a term ap- 

 plied to fuch offices and feftivals as are celebrated with lefs 

 folcmnity than the double ones ; but yet with more than the 

 fingle ones. 



The femi-double office has double vefpers, and nine lelTons 

 at matins ; but the anthems are not redoubled. It is per- 

 formed on Sundays, on the oftaves, and on the fealls marked 

 for femi-double in the calendar. 



SEMIFLOSCULOUS, a term ufed to exprefs the 

 flowers of a certain clais of plants, of which the dandelion, 

 hawkweed, and the like, are kinds. 



This fort of flower confiits of a number of femiflofculi, 

 which are diipofed into one or more circles, and all com- 

 prehended in the fame cup, which often becomes inverted 

 as the flower ripens. Thefe femiflofcules are petals, hollow 

 in their lower part, but in their upper half are flat, and con- 

 tinued in the fhape of a tongue. Thefe are often feparated 

 from each other by intermediate leaves, and are placed upon 

 the embryo fruit, from which there Hands out a flender ca- 

 pillament, divided at the end into two parts ; often carried 

 beyond the vagina, fupported by five props. The embryos 

 are placed in the thalamus, or bottom of the cup, and finally 

 become feeds, fometinies winged with down, fometimcs 

 naked, fometimes coronated, and lomclimes foliated. 



SEMIGALLIA, Duchy of, in Geography, a divifion of 

 Courland, about i lo miles in length, and from lo to 25 in 

 breadth, bounded on the north by Riilfia, from which it is 

 feparated by tiie Dwina, and elfewhere by Courland. It is 

 fubjedt to Ruflia. Its capital is Mittaw. 



SEMIGERMANjE Gentes, in .Ancient Geography, 

 the name of a people who inhabited the Pennine Alps, ac- 

 cording to Ptolemy. 



E e 2 SEMIJA, 



