HKB
In these ways all defects will be corrected, whether in metopes or intercolumniations or lacunaria, as all the arrangements have been made with uniformity.
The capitals of each triglyph are to measure one sixth of a module. Over the capitals of the triglyphs the corona is to be placed, with a projection of two thirds of a module, and having a Doric cymatium at the bottom and another at the top. So the corona with its cymatia is half a module in height. Set off on the under side of the corona, vertically over the triglyphs and over the middle of the metopes, are the viae in straight lines and the guttae arranged in rows, six guttae broad and three deep. The spaces left (due to the fact that the metopes are broader than the triglyphs) may be left unornamented or may have thunderbolts carved on them. Just at the edge of the corona a line should be cut in, called the scotia. All the other parts, such as tympana and the simae of the corona, are to be constructed as described above in the case of the Ionic order.
Such will be the scheme established for diastyle buildings. But if the building is to be systyle and monotriglyphic, let the front of the temple, if tetrastyle, be divided into nineteen and a half parts; if hexastyle, into twenty-nine and a half parts. One of these parts will form the module in accordance with which the adjustments are to be made as above described.
Thus, over each portion of the architrave two metopes and two triglyphs[3] will be placed; and, in addition, at the corners half a triglyph and besides a space large enough for a half triglyph. At the centre, vertically under the gable, there should be room for three triglyphs and three metopes, in order that the centre intercolumniation, by its greater width, may give ample room for people to enter the temple, and may lend an imposing effect to the view of the statues of the gods.
[Note 3: That is: two metopes with a triglyph between them, and half of the triglyph on either side.]
The columns should be fluted with twenty flutes. If these are to be left plane, only the twenty angles need be marked off. But if they are to be channelled out, the contour of the channelling may be determined thus: draw a square with sides equal in length to the breadth of the fluting, and centre a pair of compasses in the middle of this square. Then describe a circle with a circumference touching the angles of the square, and let the channellings have the contour of the segment formed by the circumference and the side of the square. The fluting of the Doric column will thus be finished in the style appropriate to it.
With regard to the enlargement to be made in the column at its middle, let the description given for Ionic columns in the third book be applied here also in the case of Doric.
Since the external appearance of the Corinthian, Doric, and Ionic proportions has now been described, it is necessary next to explain the arrangements of the cella and the pronaos.