dlfouldings.
Mouldings'are prismatic or annular solids, formed by plain and curved surfaces, and employed as ornamental parts in most architectural operations : All parallel sec tions of straight mouldings, and all sections passing through the axis of annular mouldings, are equal similar figures ; the forms of all mouldings are referred to a section at right angles to their longitudinal direction, when prismatic, or passing through the axis, if annular ; and this is simply denominated the Section, on account of its frequent use, as oblique sections only occur in mitres. The names of mouldings depend upon their form and situation.
If the section is a semicircle which projects from a vertical diameter, the moulding is called an Astragal, Bead, or Torus; if a torus and bead be both employed in the same order of architecture, they are only distin guished by the bead being the smallest. The tori are generally employed in bases, but the bead both in bases and capitals.
If the moulding be convex, and its section he the quar ter of a circle or less, and if the one extremity project be yond the other equal to its height, and the projecting side be more remote from the eye than the other, it is termed a Quarter Round ; this, in Roman architecture, is always employed above the level of the eye.
If the section of a moulding be concave, but in all other respects the same as the last, it is denominated a Caveat). They are never employed in bases or capitals, but frequently in entablatures.
If the section of a moulding is partly concave and partly straight, and if the straight part be vertical and a tan gent to the concave part, and if the concavity be equal or less than the quadrant of a circle, the moulding is denominated an Apophyge, Scape, Spring, or Conge : it is used in the Ionic and Corinthian orders for joining the bottom of the shaft to the base, as well as to connect the top of the fillet to the shaft under the astragal.
If the section be one part concave and the other convex, and so joined that they may have the same tangent, the moulding is named a Cymatium ; but Vitruvius calls all crowning or upper members cymatiurns, whether they resemble the one now described or not.
If the upper projecting part of the cymatium be a con cave, it is called a Cima-recta ; they are generally the crowning members of cornices, but are seldom found in other situations.
If the upper projecting part of the cymatium be con vex, it is called a cima-reversa, and is the smallest in any composition of mouldings, its office being to sepa rate the larger members: it is seldom used as a crowning member of cornices, but is frequently employed with a small fillet over it, as the upper member of architraves, capitals, and imposts.
If the convex part of a moulding recede and meet a horizontal surface, the recess formed by the convexity and the horizontal surface is termed a Quirk.
If the section of the moulding be a convex conic sec tion, and if the intermediate part of the curve project only a small distance from the greatest projecting extre mity, and if the tangent to the curve at the receding ex tremity meet a horizontal line produced forward without the curve at the upper extremity, the moulding is called an Ovolo. It is generally employed above the eye, as a crowning member in the Grecian Doric. °voles may . n be used in the same composition of different sizes ; is sometimes cut into egg and tongue, or cgg and dart, when it is termed Echinus. It is employed instead of a torus in the base of Lysicrates at Athens. 1 he contour of ovolos arc generally elliptical or hyperbolical curves.
These curves can be regulated to any degree of quick ness or flatness ; the parabola can also be drawn under these conditions ; but its curvature does not afford the variety of change of the other two species.
If the section be a concave semi-ellipse, having its con jugate diameter such that the one may unite the extre mities of its projections, and the other diameter may be parallel to the horizon, the moulding is termed a Scotia. They are always employed below the level of the eye ; their situation is between two tori. The one extre mity has generally a greater projection than the other, and the greater projection is nearest to the level of the eye.