Fig. 10. Shews the method of glueing up columns in eight staves or pieces, the whole being glued together in the manner of Figure 4. We must here observe, that the workman must be careful to keep the joints out of the flutes; for being in the fillets, there will be more substance to prevent them from giving way. No. 1. is a section of the column at the top; and No. 2. a section at the bottom. After lacing supposed to be glued together, the octagons and mitres must be laid down correctly, in order to form the jointr. truly. Here are two bevels shewn, one for try ing up the 'nitres, and the other for trying the work when put together.
Fig. 11. shews the method of glueing up the base of a column, according to the following description. Let a course, consisting of pieces of equal lengths, be closely jointed together upon a plane surface or board, so as to be something more than the diameter of the most projecting moulding in the base, then glue the joints firmly together. and plane the upper surface smooth. Upon this course lay a second, with the same number of pieces as the first, closely jointed at the ends as before, and also to the upper surface of the lower course ; glue down one of the pieces, so that the middle of its length may fall upon the joint of the two under pieces; then the others being glued on suc cessively till the space is closed, a third may be repeated in the same manner. The horizontal joints of these courses must be so regulated, as to fall at the junction of two mouldings, forming a re-entering angle. When the glue is thoroughly hardened, the base may be sent to be turned. A base, glued up in this manner, will stand much better than one which has the fibres of the wood perpendicular. No. 1. is the plan of the base. The whole lines directed to the centre, shew the joints of the upper course ; and the dotted lines tending to the same point, shew the joints of the course below.
Fig. 12. Shews the method of glueing up the modern Ionic capital. No. 1. is the plan exhibiting the manner of placing the blocks. No. 2. is the elevation of the same. The plan is here inverted.
Fig. 13. Strews the manner of glueing up the Corinthian capital for curving of the leaves. No. 1. is the plan in verted. No. 2. the elevation. The abacus is glued up in the same manner as the Ionic capital, Fig. 12.
Fig. 14. Is the method of forming a cylindrical surface, without veneers, by equidistant parallel grooves, and by inserting slips of wood in the grooves. No. 1. exhibits the
elevation, and No. 2. the plan.
Fig. 15. Shews the method of forming a conic body. The theory of this is no more than covering the trustruni of a cone ; the covering is formed by two concentric arcs, and terminated at the ends by the radii ; the radius of the one arc is the whole slant side of the cone, that of the other is the slant side of the part cut off. Here the grooves are all directed to the centre, and filled in with slips of wood glued as before, the semicircle ABC below, is the plan : the arc III must be equal to the semicircumference ABC.
Fig. 16. Is the same for a smaller segment.
Fig. 17. Shews the method of glueing up a sphere or globe, by the same method. No. I. the face of the piece ; No. 2. the edge, strewing the depth of the grooves ; No. 3. shews the mould for forming the pieces to the true curva ture; No. 4. exhibits the faces of two pieces put together.
Circular headed sash frames in circular walls. The ptinciple of a circular headed sash frame in a circular wait, depends upon the section of a cylinder, and the de velopment of the surface as cut by another cylinder. In the formation of the radial bars, two of the sides are paral lel planes, and the edges are portions of cylindrical sur faces, contained between the exterior and interior faces of the wall. To form the cylindrical surfaces of the concave and convex sides of the radial bars, it will be necessary to be informed, that the curves which direct the shape of the edges are portions of two different ellipses, formed by cut ting two different cylindrical surfaces contained between the two sides of the cylindrical wall, and concentic there with by two parallel planes, inclined at the same angle as the planes of the bar, and having their distance from one another equal to the thickness of the said bar. And, con sequently the ellipse, which directs the form of the concave edge of the bar, will have its lesser axis equal to the diame ter of the interior cylindrical surface, and that which forms the convex edge equal to the diameter of the exterior cy lindrical surface.
The circular bar, or, as it is improperly called, cod depends on the development of the part of the cylindri cal surface, formed by cutting a vertical cylinder by a num ber of horizontal concentric cylindrical surfaces, which gives the form of the veneers, or thin slices of wood to be bent in thicknesses.