2The origin and invention of the different species of columns having been discussed, it is now necessary to say something on the subject of their ornaments, how they originated, and upon what principles and for what purposes they were invented. In all buildings the timber framed work, which has various names, crowns them. The timbers vary as much in their uses as in their names. Those are called bressummers (trabes) which are placed over columns, pilasters (parastatæ), and antæ. In the framing of floors, beams (tigna) and boards (axes) are used. If the span of a roof be large, a ridge piece (columen) is laid on the top of the king post (columna, whence is derived the word column), and a tye beam (transtrum) and struts (capreoli) will be necessary. If the roof be of moderate span, the ridge piece (columen), and rafters (cantherii), of sufficient projection at their feet to throw the water off the walls, will answer the purpose. On the rafters are laid purlines (templa), and again on these, to receive the tiles, are placed common rafters (asseres), which must be of sufficient length to cover the walls and protect them.
2Thus each piece has its proper place, origin, and purpose. Hence, following the arrangement of timber framing, workmen have imitated, both in stone and marble, the disposition of timbers in sacred edifices, thinking such a distribution ought to be attended to; because some antient artificers, having laid the beams so that they ran over from the inner face of the walls, and projected beyond their external face, filled up the spaces between the beams, and ornamented the cornices and upper parts with wood-work elegantly wrought. They then cut off the ends of the beams that projected over the external face of the wall, flush with its face; the appearance whereof being unpleasing, they fixed, on the end of each beam so cut, indented tablets, similar to the triglyphs now in use, and painted them with a waxen composition of a blue colour, so that the ends of the beams in question might not be unpleasant to the eye. Thus the ends of the timbers covered with tablets, indented as just mentioned, gave rise to the triglyph and metopa in the Doric order.
3Others, in subsequent works, suffered the rafters’ feet above each triglyph, to run over, and hollowed out the projecting inferior surface. Thus, from the arrangement of beams, arose the invention of triglyphs; and, from the projection of the rafters, the use of mutuli under the corona. On which latter account it is observable, that in works of stone and marble the carving of the mutuli is inclined, in imitation of the feet of rafters, whose slope is necessary to carry off the water. Hence we have the imitation of the earliest works to account for the Doric triglyph and mutulus,
4and not, as some have erroneously said, from the circumstance of triglyphs being introduced as windows; which could not be the case, inasmuch as they are placed on external angles, and immediately over columns, in both which situations windows would be absurd, in the highest degree, for the tye at the angles of buildings would be entirely destroyed, if occupied by windows; and therefore the dentils of the Ionic orders might as properly be seen to occupy the places of windows, if the spaces occupied by triglyphs have an origin of such a nature. The intervals, moreover, between dentils, as well as those between triglyphs, are called metopæ. Besides, the Greeks, by the word ὄπαι, signify the beds of the beams, which we call cava columbaria: thus the space between two beams obtained the name of a metopa.
5As in works of the Doric order triglyphs and mutuli were first used, so in Ionic works the use of dentils was first introduced; for as the mutuli bear a resemblance to the projecting feet of the principal rafters, so, in the Ionic order, the dentils imitate the projection of the common rafters. Hence the Greeks never placed dentils below the mutuli, because the feet of common rafters cannot be below those of principal rafters. For a design must be anomalous, when that which ought to be above the principal rafters is placed below them. The antients, therefore, neither approved nor used mutuli nor dentils in the cornices of their pediments, but coronæ simply; because neither principal nor common rafters tail on the front of a pediment, neither can they project beyond it, their direction being towards the eaves. Their opinion, therefore, evidently was, that a distribution would not be correct in a copy which could not exist in the prototype.
6For the perfection of all works depends on their fitness to answer the end proposed, and on principles resulting from a consideration of Nature herself, and they approved those only which, by strict analogy, were borne out by the appearance of utility. Their principles were thus established, and they have left us the symmetry and proportion of each order. Following their steps, I have already spoken of the Ionic and Corinthian orders: I shall now proceed to give a succinct account of the Doric order, and its most approved proportion.