" Figure 6 is a circular flowing and winding soffit, in a straight wall. Continue the flowing of the jambs till they meet at a ; then draw the arch-line b c, and make the chords equal to the circumference of the lesser arch, on which set the parts it is divided into, 1, 2, 3, 4 ; divide the distance of the chord from the arch into five parts; draw a line from 3 to b, and mark where it cuts the perpendicular 4 at d; draw a line from d to 1, parallel to the chord-line ; divide 1 2 into four parts ; from two of them draw a line parallel to 1 d; mark where it cuts the perpendicular of 3, on the chord-line at c; draw another parallel line from the third mark, and mark its crossing the perpendicular of 2, on the chord-line at h; trace through the points b, d, e, 2, this gives one side of the soffit, then take the ordinates across the plan, 1 1, 2 2, 3 3, 4 4, and the side of the flew a f, and set them from 2, It, c, d, b ; then take the parts 1, 2, 3, 4, of the greater arch, and set them from 1 to 2, 3, 4, f; trace through them, and get the other side; set oil' these ; measure to the other half, and complete the soffit." Plate II. Figure 1.-A soffit, from the Practical House Carpenter. No. 1, is the plan and section of the centre. No. 2, is the covering extended in piano. The author describes it thus : "Figure a the plan of a circular wall, wherein a circular door, or window, is to be fixed ; to make a soffit to fit or stand on the plan, as Figure D ; draw the base-line of the arch, or soffit, to touch the bow of the wall ; divide the arch-line into twelve parts, and drop them down to the plan across it ; then stretch out the arch, as 1 to 12, and draw the divisions at right angles from it ; then take them from the base-line to the wall, as 1, 2, 3, 4, &c., and transfer them on the parts of the line stretched out, will give the edge of the soffit Figure 2.-A cylindrical soffit, cutting obliquely through a straight wall, from the Practical House Carpenter. The
author describes it thus: "Figure E is a soffit in a straight wall on flewing jambs: v the soffit stretched out ; stretch out the arch, as o to 8, and draw lines from those divisions parallel with the jambs ; then draw the lines from the divi sions on each side of the plan ; the angle of meeting will give the edge of the soffit." This description is imperfect : for the true method, see the article ENVELOPE.
Figure 3.-A cylindrical soffit in a circular wall, from Pain's Practical Builder. The author describes it thus : "Figure A is a circular wall, which has a door or window, that stands flewing. Because the jambs do not stand at right angles with the diameter of the circle, find the curve-line of • the soffit in this case ; draw the chord-line or base-line, of the arch, a 9, at right angles with the jambs o, h, to touch the arch of the wall at a, and divide the arch into equal parts, and drop them to the wall ; then take off the distances 11 g, 8, 9, 7, f, 0, e, &c., and put them on the arch stretched out, gives the edge of the soffit." It is singular, that this method should be true, while the former, which is more simple, is false.
Figure 4.-A cono-cuneoidal soffit in a circular wall. No. 1 is the plan and sections of the centre : No. 2, the soffit stretched out.
Figure 5.-A conical soffit in a cylindrical wall, where the aperture expands towards the concave surface of the wall.
Figure 6.-A conical soffit in a circular wall, where the aperture expands towards the convex surface of the wall.
Figure 7.-A cono.cnneoidal soffit in a circular wall, where the aperture expands towards the convex surface of the wall.
These Figures, viz., 4, 5, 6, 7, arc from Pain's Golden Rule. The principles upon which they are founded are erroneous : see the article ENVELOPE; where are given correct methods for Figures 5 and 6, and very near approximations for Figures 4 and 7.