[A] Though the proportions given are approximately accurate for general division, it will be found necessary in detailing to adopt a more intimate system of measurement. In the following diagrams the diameter is divided into 36 parts, which are expressed in figures, giving heights, etc., of the various features. _Doric Capital_ The Doric abacus consists of a rectangular slab, square on plan, which in detail consists of a fillet and reversa moulding surmounting a facia. Its extreme width is one and a half times the upper diameter. The square abacus is supported by an ovolo, which is circular on plan, and is connected with the necking by three small fillets. [Illustration: No. 159. Doric Capital.] The capital is half a diameter in height, exclusive of the mouldings between the necking and the shaft, and the upper part to the underside of the ovolo occupies rather more than half. [Illustration: No. 160. Ionic Capital.] The necking is a vertical extension of the upper diameter of the column, and is separated from the shaft by a boldly projecting moulding, which in height should be about equal to the three small fillets below the ovolo. The moulding consists of a torus and a fillet, and a cavetto curve is carried from the underside of the fillet and dies into the line of the shaft of the column. Sometimes the ovolo is decorated with its characteristic egg and tongue detail, and occasionally the reversa of the abacus is also enriched. The necking is sometimes ornamented with four rosettes, which are placed centrally under the square faces of the abacus. _Ionic Capital_ The Ionic capital is half a diameter high, and is readily distinguished by its bolster-like form with voluted ends. This bolster is rectangular on plan, and measures laterally rather more than one and a half diameters, while from back to front it is slightly less than a diameter. The shaft terminates in a cavetto curve, and is surmounted by a fillet, a small torus and an ovolo moulding, which is invariably decorated with egg and tongue detail. These mouldings all conform to the circular plan of the shaft. On the ovolo rests the voluted bolster. The abacus, which is square on plan, consists of a reversa moulding and fillet. From the top of the abacus to the base of the ovolo the height is about a third of a diameter, and one-fourth of this height will give the height of the abacus. The centre or eye of the volute can readily be found by dropping a perpendicular from the lower edge of the reversa to intersect the horizontal line defining the base of the ovolo. This point of intersection is the required centre. _To Draw the Volute_