‹‹‹ Vitr. 3.5.6 | Table of Contents | Vitr. 3.5.8 ›››
7The heights of the parts of the capital are to be so regulated that three of the nine parts and a half, into which it was divided, lie below the level of the astragal on the top of the shaft. The remaining parts are for the cymatium, abacus, and channel. The projection of the cymatium beyond the abacus is not to be greater than the size of the diameter of the eye. The bands of the pillows project beyond the abacus, according to the following rule. Place one point of the compasses in the centre of the eye, and let the other extend to the top of the cymatium, then describing a semicircle, its extreme part will equal the projection of the band of the pillow. The centres, from which the volute is described, should not be more distant from each other than the thickness of the eye, nor the channels sunk more than a twelfth part of their width. The foregoing are the proportions for the capitals of columns which do not exceed fifteen feet in height: when they exceed that, they must be otherwise proportioned, though upon similar principles, always observing that the square of the abacus is to be a ninth part more than the diameter of the column, so that, inasmuch as its diminution is less as its height is greater, the capital which crowns it may also be augmented in height and projection.
7The height of the capital is to be such that, of the nine and a half parts, three parts are below the level of the astragal at the top of the shaft, and the rest, omitting the abacus and the channel, belongs to its echinus. The projection of the echinus beyond the fillet of the abacus should be equal to the size of the eye. The projection of the bands of the cushions should be thus obtained: place one leg of a pair of compasses in the centre of the capital and open out the other to the edge of the echinus; bring this leg round and it will touch the outer edge of the bands. The axes of the volutes should not be thicker than the size of the eye, and the volutes themselves should be channelled out to a depth which is one twelfth of their height. These will be the symmetrical proportions for capitals of columns twenty-five feet high and less. For higher columns the other proportions will be the same, but the length and breadth of the abacus will be the thickness of the lower diameter of a column plus one ninth part thereof; thus, just as the higher the column the less the diminution, so the projection of its capital is proportionately increased and its breadth is correspondingly enlarged.