Perspective and geometrical drawing adapted to the use of candidates for second and third-class teachers' certificates . by rectangular planes, A pyramid is a solid formed by joining the angles of atriangle, square, etc, with some external point. If the exter-nal point be vertically above the centre of the pyramid, thepyramid is said to be right; if in any other position, oblique, A frustum of a pyramid is the part remaining after asmaller pyramid is cut off loj a plane parallel to the base. Of solids with convex surfaces:— A sphere is formed by the revolution of a semicircle aroundthe diamete
Perspective and geometrical drawing adapted to the use of candidates for second and third-class teachers' certificates . by rectangular planes, A pyramid is a solid formed by joining the angles of atriangle, square, etc, with some external point. If the exter-nal point be vertically above the centre of the pyramid, thepyramid is said to be right; if in any other position, oblique, A frustum of a pyramid is the part remaining after asmaller pyramid is cut off loj a plane parallel to the base. Of solids with convex surfaces:— A sphere is formed by the revolution of a semicircle aroundthe diameter, which remains fixed. A cone is formed by the revolution of a right-angledtriangle around one of the containing sides, which remainsfixed. A cylinder is formed by the revolution of an oblong aroundone side, which remains fixed. A spheroid is formed by the revolution of a semi-ellipsearound one of the axes, which remains fixed. If the fixed axis be major^ the spheroid is prolate • if^QfiinoT^ oblate. DRAWING. Tine Cube. The drawing of the cube is so simple that a single examplewill suffice for its THE CUBE. 67 Example 1,—Draw a cube, edge 4, placed on , one sideparallel to and 2 within it, near angle 3 to right. H = 6; = i\ scale ^ = V, Draw , , and O, and find IMP as A 3^ to right, and B 4 to right of A; take 0 2 to leftof A, and D M to left of 0; join A , D MP andC MP, cutting A in F and E. On AB describe squareASMB; join S , M and B ; through E and Fdraw parallels to AS, meeting S in H and G; throughG, H draw parallels to SM, meeting M in K and LN from L J_ to MB, and EN from E parallel to will complete the required cube. For XA = 3, andAE = AC = 2, AF = AD and EF = CD = AB = 4; also FG==EH = AS = 4, and GK = HL = EN = AB = 4: thenEF = GH= KL=4, etc. (Fig. 38.) 68 DRAWING. The Pllntti.
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Keywords: ., bookcentury1800, booksubjectgeometricald, booksubjectperspective
