We will bring this chapter to a conclusion by giving an example of an ornamental tapered base made up of flat surfaces.
A plan and elevation of the base is shown in Fig. 57. On examination it will be seen that the square top is twisted diagonally to the bottom.
The triangle A C C on the pattern is struck out by making A B equal to a' b', and B C equal to b c. The point C is then used as a centre, and the arc passing through A A' drawn. The compasses are next fixed to the distance a a, and the point A' determined by cutting the arc from the point A as centre. The whole pattern could in this way be built up by adding triangle to triangle; but, as the figure is symmetrical, it is better to disect A A' in D, and draw the lines C D and B A, produced to meet in O, using this latter point as a centre to draw the arc, as shown, upon which the rest of the pattern can be constructed. Five lengths are stepped along the outer arc, the last two being halved, this way insuring the seam lines being in their correct position.
A somewhat peculiar case of the above kind of base is when the top square is the same size as the bottom one, the pattern then coming out as a rectangle, and being built up with triangles, as in the pattern given above.