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Show A LESSON IN MATHEMATICS. There aro some pioposlllons In mathematics that wo cop prove vvlth perfect accuiacy without mnklng uu of Hguiea There, foi example, Is tint well-known theorem of plane geometry tho suifnce of a rphen; Is equal to four times the surface of a great circle That leads as if we weie going to give )0u something dry and uninteresting:, but read on and you will find It just tho other wa), foi we are going to tell you how you inn) prove that proposition with a t roquet ball and a piece of cord. Ihe croquet ball Is a sphere, and tho section nude In It by pissing a plane through Its center is a great circle The radius of tho great circle, therefore, Is cxictl) equal to tho radius of tho sphere, , Now. rav the bill through tho center, thus dividing It Into two hemispheres, and. lolnv; one of them on the tuhlo, vvlth the Hat pirt down, drlvo a small nntl ln the tenter of the round, or upper up-per part lo tho nail tie tho end nt a cord, and then wind tho coid around the mil and the luunded surface of tho half lull until this surface Is entirely coveied by the cord Cut tho cord wheie you stop winding. Then tnko the other half of the bail and drive a small null in tho renter of Its fiat part. t)lng to tho n ill a piece of coid cxaitly like the piece Hrst used nnd wind It around the nail, spirally, pressing it down so thnt It will lie Hat on tl surface of the elicle. Cut tho cord when the surfiro of the olrelo is entirely covered, and when )ou compare com-pare tho two cords )nu will find tint the piece Hrst ufed Is exactly twice us long as tho scond This pinves that the surficc of the hemlsrhere is equal to twice the surface sur-face of a great elide, nnd tint, theie fore, the surfuce of a whole sphere Is equal to four times tho surface of u great circle Ho that we demonstrate an Important theorem of geometry simply by uslllj a ball and a cord |