S E G 5,j0 SED

the line of equal parts, to the number on each leg expressing itslength. The sector remaining thus, set off the length of eacli ofthe other lines parallel to the former, and the number each of themfalls on will express its length. 3. A right line being given, andthe number of parts it contains, suppose 120, to take from it ashorter line, containing any number of the same parrs, suppose 25.Take the given line in your compass, open the sector till thetwo feet fall on 120 on each leg ; then will the distance between£5 on one leg, and the same number on the other, give the linerequired. 4. To multiply by the line of equal parts on the sector.Take the lateral distance from the centre of the line to the givenmultiplicator; open the sector till you fit that lateral distance tothe parallel of 1 and 1, or 10 and 10, and keep the sector in thatdisposition ; then take in the compasses the parallel distance of themultiplicand, which distance, measured laterally on the same line,will give the product required. Thus, suppose it were requiredto find the product of 8 multiplied by 4: take the lateral distancefrom the centre of the line to 4 in your compasses, i. e. place onefoot of the compasses in the beginning of the divisions, and extendthe other along the line to 4. Open the sector till you fit thislateral distance to the parallel of 1 and 1, or 10 and 10. Thentake the parallel distance of 8, the multiplicand; i. e. extend thecompasses from 8, in this line, on one leg, to 8 in the same line onthe other; and that extent, measured laterally, will give the pro-duct required. 5. To divide by the line of equal parts on thelector, Extend .the compasses laterally from the beginning of theJlne to 1, and open the sector till you fit that extent to the paral-lel of the divisor; then take the parallel distance of the dividend,which extent, measured in a lateral direction, will give the quo-tient required. Thus, suppose it was required to divide 36 by 4 ;extend the compasses laterally, from the beginning of the line to 1,and fit to that extent the parallel of 4, the divisor ; then extend thecompasses parallel, from 36 on one leg, to 36 on the other, andthat extent, measured laterally, will give 9, the quotient required.6. Proportion by the line of equal parts. Make the lateral dis-tance of the second term the parallel distance of the first term, theparallel distance of the third term is the fourth proportional. Ex-ample. To find a fourth proportional to 8, 4, and 6, take the late-ral distance of 4, and make it the parallel distance of 8 ; then theparallel distance of 6, extended from the centre, shall reach to thefourth proportional 3. In the same manner, a third proportionalis found to two numbers. Thus, to find a third proportional to 8and 4, the sector remaining as in the former example, the paralleldistance of 4, extended from the centre, shall reach to the thirdproportional 2. In all these cases, if the number to be made a pa-rallel distance be too great for the sector, some aliquot part of it isto be taken, and the answer is to be multiplied by the number bywhich the first number was divided.

Sector, Use of the Line of Polygons on the. 1. Toinscribe a regular polygon in a given circle. Take the semidia-meter of the given circle in the compasses, and adjust it to thenumber 6, on the line of polygons, on each leg of the sector; then,the sector remaining thus opened, take the distance of the twoequal numbers, expressing the number of sides the polygon is tohave; e. gr. the distance from 5 to 5 for a pentagon, from 7 to 7tor a heptagon, &c. These distances carried about the circum-ference of the circle, will divide it into so many equal parts. 2.To describe a regular polygon, e. gr. a pentagon, on a given rightline. Take the length of the line in the compasses, and apply itto the extent of the number 5, 5, on the lines of polygons. Thesector thus opened, upon the same lines take the extent from 6 to6 ; this will be the semidiameter of the circle the polygon is to beinscribed in. If then, with this distance, from the ends of thegiven line, you describe two arches of a circle, their intersectionwill be the centre of the circle.

Sector, Usf of the Lines of Sines, Tangents , andSecants, on the. Dy the several lines disposed on the sector,w'e have scales to several radii; so that having a length or radiusiven, not exceeding the length of the sector when opened, wend the chord, sine, &c. thereto ; e. gr. suppose the chord, sine,or tangent, of 10 degrees, to a radius of 3 inches required ; make3 inches the aperture, between 60 and 60, on the lines of chords ofthe two legs; then will the same extent reach from 45 to 45 onthe line of tangents, and from 90 to 90 on the line of the sines onthe other side; so that to whatever radius the line of chords is set,

to the same are all the others set. In this disposition, therefore, ifthe aperture between 10 and 10, on the lines of chords, be takenwith the compasses, it will give the chord of 10 degrees. If theaperture of 10 and 10 he in like manner taken on the lines of sines,it will be the sine of 10 degrees. Lastly, if the aperture of 10 and10 be in like manner taken on the lines of tangents, it gives thetangent of 10 degrees. If the chord, or tangent, of 70 degreeswere required ; for the chord, the aperture of half the arch, viz.35, must be taken, as above; which distance, repeated twice,gives the chord of 70 degrees. To find the tangent of 70 degreesto the same radius, the small line of tangents must be used, theother only reaching to 45: making, therefore, 3 inches the aper-ture between 45 and 45 on the small line; the extent between 70and 70 degrees on the same, will be the tangent of 70 degrees to3 inches radius. To find the secant of an arch, make the givenradius the aperture between 0 and 0 on the lines of secants ; thenwill the aperture of 10 and 10, or 70 and 70, on the said lines,give the secant of 10° or 70°. If the converse of any of thesethings were required, that is, if the radius be required, to which agiven line is the sine, tangent, or secant, it is but makingthe givenline, if a chord, the aperture on the line of chords, between 10and 10, and then the sector will stand at the radius required ; thatis, the aperture between 60 and 60 on the said line, is the radius.If the given line were a sine, tangent, or secant, it is but the mak-ing it the aperture of the given number of degrees; then will thedistance of 90 and 90 on the sines, of 45 and 4J on the tangents,of 0 and 0 on the secants, be the radius.

SECULAR, a person who lives at liberty in the world, notshut up in a monastery, in which sense it stands opposed to regu-lar. The Romish clergy are divided into secular and regu-lar, of which the latter are bound by monastic rules, the formernot.

Secular Games, in antiquity, solemn games held amongthe Romans once in an age. These games lasted three days andas many nights; during which time sacrifices were performed,theatrical shews exhibited, with combats, sports, &c. in thecircus.

Secular Poem, a poem sung or rehearsed at the seculargames; of which kind we have a very fine piece among the worksof Horace , being a sapphic ode at the end of his epodes.

SECULARIZATION, the act of converting a regular person,place, or benefice, into a secular one.

SECUNDARA, a town of Hindoostan, in the country ofDelhi, 28 miles S. E. of Delhi, and 68 N. of Agra . Lon. 78. 7.E. Lat. 28. 22. N.

SECUND1NES, in anatomy, are the chorion and amnios, withthe placenta, &c. See Anatomy.

SECURIDACA, a genus of plants of the class diadelpbia, andorder octandria. Calyx three-leaved, small, deciduous, coloured ;corolla papilionaceous, vexilium consisting of two petals, oblong,straight, conjoined to the carina at the base ; legume ovate, uni-locular, monospermous, ending in a ligulated ala. There are thre»species.

SECURIS, [Lat.] In Roman antiquity, the axe, which formedan essential part of the fasces.

SECUTORES, a species of gladiators among the Roman*whose arms were a helmet, a shield, and a sword or a leadenbullet.

Secutores was also a name given to the gladiators who tookthe place of those killed in the combat, or who engaged the con-queror. This post was usually taken by lot.

SEDAN, in geography, a town of France , in the departmentof Ardennes, and pro vince of Champagne , seated on the river Maese,26 miles S. E. of Charlemont, and i35 N. E. of Paris . Lon. 5.2. E. Lat. 49. 42. N.

Sedan-Chair, a covered vehicle for carrying a single person,suspended by two poles, and borne by two men, hence denomi-nated chairmen.

SEDATIVES, in medicine, a general name for such medicine*as weaken the powers of nature, such as blood-letting, coolingsalts, purgatives, &c.

SE DEFENDENDO, in law, a plea used for him that ischarged with the deatli of another, by alledging that he was undera necessity of doing what he did in his own defence.

SEDGLEY, a manufacturing town of England, in Stafford-shire .