The preceding three problems treat of the various miters involved in the construction of angular pediments. In Fig. 393 is shown an elevation of a curved or segmental broken pediment in which the normal profile is placed in the horizontal return at the foot. The profiles for the curved molding and for the return at the top can both be obtained at one operation in the following manner: Divide the normal profile ABC into any convenient number of parts, and from the points thus obtained draw lines at right angles to the horizontal line C F of elevation, as shown. At any convenient point draw G H, at right angles to A G, cutting them. With Q, the point from which the curve of the molding was struck, as center, strike ares from the points in ABC, extending them in the direction of D indefinitely. From any convenient point in the arc A D, as L, draw a line to the center Q. From L draw L M, at right angles to L Q, upon which, beginning at L, set off the distances contained in H G, as shown by the small figures in L M. From the points of intersection where arcs struck from Q cut L Q draw lines at right angles to L Q. From the points in L M, and at right angles to it, drop lines cutting those of similar number drawn at right angles to L Q. A line traced through these points of intersection, as shown by M K, will be the profile of curved molding. It will be observed that the points for obtaining the profile are where be perpendiculars dropped from L M intersect the lines drawn at right angles to L Q, and not where the perpendiculars dropped from L M intersect the arcs.
For the profile D E draw N D, parallel to C J, or at right angles to N O, and, starting from D, set off on D N the same points as are in G H. Drop perpendiculars from these points to the ares of similar numbers drawn from A B, when a line traced through the points of intersection will form the desired profile, as show by D E. The normal profile is also drawn above G H and N D at X and Z to show that the same result is obtained by using the points in G H to set off on L M and N D as would be obtained by dropping the points from the profiles. The patterns for the returns would be obtained as described in the previous problems.
Fig. 393. - To Obtain the Profiles and Patterns of the Returns at the Top and Foot, of a Segmental Broken Pediment.
Problems describing the method of obtaining the pattern for the blank for the curved molding will be found in Section 2 of this chapter.