These two plates depict the two major alternative forms of the Ionic capital. Plate 20 shows the four-sided capital developed by Scamozzi, and plate 21 a parallel-sided capital from Greek and Roman sources. Ionic capitals are not difficult to set out once the drawing of the volute has been mastered, and there is a degree of latitude in the location of their essential elements.
Plate 20 shows elevations of the capital both from the side and across the diagonal. As the plan shows, the four double-sided volutes are arranged radially, the centre-lines of each pair being mutually at right angles, each at 45° to the plane of the face of the entablature above. The faces of the volutes close together at their extremities, and are inclined inwards slightly towards the bottom. The spiral fillet containing the volute moves gradually outwards from the face as it tightens so that the central eye stands proud of the rest. Each of the pairs is connected by a kind of web, and each pair stands clear of the ovolo and astragal mouldings which form a kind of extension of the column shaft and complete the essential construction of the capital. Ovolo and astragal are enriched with egg and dart and bead and reel respectively, the setting out related to a fluting pattern of twenty-four flutes to the shaft circumference, as shown on the plan. The abacus is moulded in three sections and has four main concave faces corresponding with the tapering volutes below and truncated by a short square face on the diagonal. The setting out of the abacus on plan corresponds with that for the Corinthian order, shown in plate 26. Each face of the abacus carries a central flower.
To draw the capital in elevation it is best to begin by marking out a series of horizontal lines to give the vertical subdivisions. Although the overall height of the capital is 0.5 diameters, this overlaps the shaft by a considerable amount, the upper edge of the ovolo being only 0.2 diameters below the top of the abacus. The eye of the volute should then be established. Vertically, it corresponds with the astragal around the head of the shaft. Horizontally it lies on the edge of the shaft profile, the centres of the eyes of each face of the capital being 0.82 diameters apart. The eye being established, the volute is then drawn according to the method preferred (plate 18, for example) noting that its upper sweep overlaps the lower element of the abacus right up to the lower edges of its central fillet, and then curves down to disappear behind the ovolo. Most authorities add, as well as the flower decorating the abacus, a small acanthus leaf under the abacus on the short diagonal face, and another trailing in the acute angle inside the upper sweep of the volute.
The Greek derived parallel-sided capital shown in plate 21 is different in a number of respects. The top of the shaft and its superimposed, concentric abacus and ovolo are similar,
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20. THE IONIC CAPITAL I
though the ovolo itself is slightly less pronounced. The abacus is smaller than in the four-sided version, fractionally larger than the column diameter at 1.05 diameters overall, and is a plain square on plan, with a cyma reversa under a fillet. The volutes are similar in size, but on each principal face the eyes are 0.95 diameters between centres, giving an overall capital width of 1.35 diameters, as opposed to 1.5. The volutes are connected by a plain web which fills the space between abacus and ovolo, and each pair of volutes is joined across the end of the capital in a scroll of complex form, normally pinched upwards and inwards in the centre and hugging the rounded shape of the central astragal and ovolo. The abacus of either version may be enriched. Plate 21 shows a leaf pattern of Greek derivation. The parallel-sided capital is perhaps more appropriate to pilaster orders, where the omission of the back half of the capital is not obvious, but is awkward for orders which return on the flank of a building, unless the volute on the corner is pulled forward diagonally and given a second face, in imitation of a four-sided capital.
21. THE IONIC CAPITAL II
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