ON THE FIVE ORDERS USED BY THE ANCIENTS. CHAP. XII.

An engraving of a classical column shaft, likely Ionic based on the base and capital details, illustrating entasis. A vertical line to the right of the shaft shows the profile. Point A is at the base. Point B marks the first third of the shaft's height, where the straight part ends and the curve begins. Point C marks the top of the shaft just below the collarino. The diagram demonstrates how the upper two-thirds of the column diminish in thickness along a curve.

THERE ARE FIVE orders which the Ancients employed: namely, the Tuscan, Doric, Ionic, Corinthian, and Composite. These must be arranged in buildings in such a way that the most solid is at the lowest part, because it will be much more capable of sustaining the weight, and the building will come to have a firmer foundation. Therefore, the Doric shall always be placed under the Ionic; the Ionic under the Corinthian; and the Corinthian under the Composite. The Tuscan, being crude original: "rozzo", is rarely used above ground except in buildings of a single order, such as villa roofs; or in very large structures, such as Amphitheaters and the like, which, having multiple orders, will have this one placed in the position of the Doric, under the Ionic. And if one wishes to omit one of these, such as placing the Corinthian immediately above the Doric, this may be done, provided that the most solid is always in the lower part, for the reasons already stated. I will set down the measurements of each of these separately, not so much according to what Vitruvius Marcus Vitruvius Pollio, the Roman author of 'De architectura' teaches us, but according to what I have observed in Ancient buildings; but first, I will discuss those things which apply generally to all of them.

ON THE SWELLING AND DIMINUTION OF COLUMNS, INTERCOLUMNATIONS, AND PILASTERS. Cap. XIII.

THE COLUMNS of each order must be formed in such a way that the upper part is thinner than the lower part, and that they have a certain swelling entasis|the slight convex curve in the shaft of a column, introduced to correct the optical illusion of concavity in the middle. Regarding the tapering original: "diminutione", it is observed that the longer the columns are, the less they should taper; this is because the height itself creates the effect of tapering through distance. Therefore, if the column is up to fifteen feet high, the thickness at the bottom should be divided into six and a half parts, and the thickness at the top shall be five and a half of those parts. If it is from 15 to 20 feet, the bottom thickness shall be divided into 7 parts, and 6 and a half shall be the top thickness. Similarly, for those from 20 to 30 feet, the bottom thickness shall be divided into 8 parts, and 7 of those shall be the thickness at the top. Thus, columns that are taller shall be diminished in the same manner by the proportional part, as Vitruvius teaches us in Chapter 2 of the 3rd Book.

But as to how the swelling should be made in the middle, we have nothing from him but a simple promise; and therefore, various people have spoken of this in different ways. I am accustomed to making the sacoma|a profile, template, or mold used for shaping architectural members of said swelling in this manner: I divide the shaft of the column into three equal parts, and I leave the bottom third straight and plumb. At the edge of the end of this third, I place a somewhat thin rod original: "riga sottile", as long as the column or a little more, and I move that part which extends from the third upward, bending it until its tip reaches the point of the upper tapering of the column below the collarino|the 'little collar' or necking of a column just below the capital, and I mark according to that curvature. Thus, the column becomes somewhat swollen in the middle and tapers very gracefully. And although I have not been able to imagine any other method shorter and more expeditious than this, or one that succeeds better, I am nonetheless greatly confirmed in this invention of mine since it so pleased Master Pietro Cattaneo A Sienese architect and author of an influential 1554 treatise when I told him of it, that he placed it in one of his works on Architecture, with which he has notably illustrated this profession.

A, B, The third part of the column, which is left straight and plumb.
B, C, The two-thirds that go on tapering.
C, The point of diminution below the collarino.

The intercolumnations intercolunnij|the proportional spacing between the shafts of columns—that is, the spaces between the columns—can be made of one and a half diameters of a column (taking the diameter at the lowest part of the column); of two diameters; of two and a quarter; of three; and even greater.