S E G 



S E G 



that the angle included by a tangent to a circle and a chord, 

 dra\Tn fron:i the point of contaft, is equal to the angle in the 

 alternate fegment. 



Some alfo call the two mixed angles comprehended be- 

 twoen the two extremes of the chord and the arc, angles of 

 the fegnunl ; but thofe are in reality the fame with thofe of 

 the chord and tangent. 



Segment, Angle in the. See Angle. 

 Seg-Mknt.s, Similar. See Similar. 



The height of a fegment D E, and half its bafe, or chord, 

 A E, being given, to find the area of the fegment. Find 

 the diameter of the circle. On this defcribe a circle, and 

 draw the bafe of the fegment A B ; draw the radii A C, 

 B C ; and find the number of degrees of the arc A D B. 

 From the diameter had, and its ratio to the periphery, find 

 the periphery itfelf ; and from the ratio of the peripiiery to 

 the arc A D B, and the periphery itfelf, find the length of 

 the arc A D B. This done, find the area of the fedlor 

 A D B C A i and that of the triangle AC B. La'Uy, fub- 

 traft the triangle from the fetlor, and the remainder is the 

 area of the fegment. 



If the area of the greater fegment B F A were required, 

 the triangle A C B mull be added to the fediors A C F and 

 B C F. For other methods of finding the area of a fegment 

 of a circle, we refer to Hutton's Menfuration, p. 133, &c. 



Segment of a Sphtre, is a part of a fphere terminated by 

 a portion of its furface, and a plane which cuts it off, pafling 

 fomewhere out of the centre. This is more properly called 

 s^feSion of a fphere. 



The bafe of fuch a fegment, it is evident, is always a circle 

 whofe centre is in the axis of the fphere. 



The folid content of a fegment of a fphere is found, by 

 multiplying the furface of the whole fphere by the altitude 

 of the legment, and then dividing the product by the dia- 

 meter of the fphere, and to" the quotient adding the area 

 of the bafe of the fegment : or, if it be lefs than a hemi- 

 fphcrc, thus ; take the altitude of the fegment from the radius 

 of the fphere, and by the difference multiply the area of the 

 bafe of the fegment, and fubtraft this produft, from that 

 which will arife by multiplying the femi-axis of the fphere 

 into the convex lurface of the fegment ; then divide the re- 

 mainder by 3, and the quotient is tlie folidity fought. 



The latter method fuppofes the axis of the" fphere to 



be given ; if not, it may be found thus ; let the altitude 



of the fegment be called a, and its femidiameter, j, then will 



ss ss 



a:s::s: — ; add — to a, and that fhall give the axis fought. 



See Frustum, and Sphere. 



Segment, Refljlance of a. See Resistance. 



Segment is fometimes alfo extended to the parts of ellip- 

 fes, and other curvilinear figures. 



Segments, Line of. On Gunter's feftor there are 

 ufually two lines, called lines of fegmcnts ; they are numbered 

 with 5, 6, 7, 8, 9, 10, and lie between the lines of fines, and 

 thofe of fuperficies. They reprefent the diameter of a circle, 

 fo divided into one hundred parts, as that a right line drawn 

 through thofe parts, and normal to the diameter, (hall cut the 

 circle into two fcgments, of which the greater fliall have that 

 proportion to the whole circle, which the parts cut have to 

 one hundred. 



SEGMENT-jLi-jif^, a denomination given by botanids to 

 thole leaves that are cut and divided into many flircds, or 

 flice'!, as fennel, &c. 



SEGMENTUM, among the Romans, an ornament of 

 lace ufed by the women on their fhoulders, which, according 

 to fome, refemblcd our Ihoulder-knots. 



Segmenta were likcwile a kind of teflcllated or Mofaic 



pavements, made up of pieces of various lliapes and colours, 

 but which had an uniform and regular arrangement. 



SEGMOIDAL Valves, \n Anatomy, are little valves of 

 the pulmonary artery ; thus called from their refembling 

 fegments of circles, but more ufually called yf/niVuna/- 'Uiz/««. 



SEGNA, in Geography, a fea-port town of Morlachia, 

 on the coaft of the Adriatic, declared a free port, and 

 erefted into a bifhopric by the emperor Jofeph II., in the 

 year 1785. It is a free town, under the proteftion of 

 Aullria. The city is ill built, worfe paved, and weakly- 

 fortified. It lies on the brink of the fea, on a foundation 

 of concreted ground, at the mouth of 3 narrow valley, fur- 

 rounded by marble hills. Segna is fuppofed to have been 

 formerly fitnated almoll; three miles farther from the valley, 

 on a fpot where are found traces of ancient habitations and 

 funeral monuments. The fea feems to have covered the 

 bottom of the valley as far as the city, which ftood on the 

 fide of a hill, and formed a tolerable harbour. The walls 

 of this city were not conftrufted before the l6tli century; 

 and this, together with other circumftances, affords a 

 further proof that Segna does not occupy the fcite of the 

 ancient Senia. The wind from the mountains fometimes 

 blows with fnch violence, that it is dangerous in winter to 

 encounter it in the ftreet. Horfes loaded with fait are fre- 

 quently thrown down in the market-place of Segna ; and 

 the roofs of houfes, though covered with heavy (tones, are 

 removed. When hurricanes occur, the (hips that happen 

 to be in the harbour run the greateil rifle of being loft ; nor 

 are they preferved without great labour and expence. The 

 fea in the mouth of the channel of Segna, oppofite to the 

 valley, is hardly ever calm ; but notwithftandmg all thefe 

 perils and difallers, the inhabitants had, about the begin- 

 ning of the lail century, fifty merchant- (hips at fea ; and 

 they acquired wealth by exporting the corn, wood, wax, 

 honey, tar, and iron of the Turkifh ftate, on which they 

 border, as well as the timber felled in the ancient forefts of 

 Vilebich ; and by importing, befiJes many other articles of 

 merchandize, fait, oil, and wine, for the fupply of the in- 

 terior provinces. At length, however, the inconvenience 

 of their fituation difconcerted their marine and commercial 

 enterprifes, fo that at prefent Segna has but few (liips be- 

 longing to it. Another damage was fullaincd by this city, 

 in coniequence of the regulation made by the court of 

 Vienna in 1741, which deprived it of 60,000 fiorius a-ycar 

 in money, 40,000 ells of cloth, and 20,000 meafures of 

 grain, given yearly by the emperor to the inhabitants of 

 Segna, who were a warlike people, and formed a kind of 

 barrier againft the Turks on that fide. When the Aullrians 

 took the country of Lika from the Turks, and formed all 

 the inhabitants into militia, Segna loll its importance. The 

 foil is fo unproduftive, that, witli the utmolt labour, it 

 fupplies fcarcely provifions fufficicnt for two months i[i the 

 year ; and they arc under a neceflity of procuring water from 

 a fpring at the diftance of twelve miles. The population 

 of Segna is at prefent computed at lefs than 7000 ; and yet 

 the people, amidil all their diladvantages, mauifeil a civility 

 aud politenefs ot manners, which are not met with in any 

 other place of the Aullrian coall, nor even among the Ve- 

 netian fubjefts of thefe parts. N. lat. 45° 4'. E. long. 



'5° .V- 

 SEGNI, Bernardo, in Biography, an early Italian 



hillorian and man of letters, wa^ born at Florence about 

 the clofe of the 15th century. He was educated at Padua, 

 where he purfucd with great alFiduity the Ihidy of the 

 Latin and Greek languages. He then engaged in legal 

 purfuits, which were interrupted by a commillion from liis 

 father to manage fome commerci.il bufinefs at Aquila. Re- 

 3 turning 



