In connection with the Roman orders it is well to keep in mind that the pedestal is one-third, and the entablature one-fourth, the height of the column in all cases.

To find the semi-diameter of the column in any order, divide the height to be occupied by the number of modules in the given order. Thus, if the given height is 23 ft.9 in. and the order is the Ionic, with the pedestal, the semi-diameter, or module, will be 23 ft. 9 in. / 28 1/2 = 10 in.; if without the pedestal; the module will be 23ft, 9in./22 1/2

=12 2/3 in. The lower one-third of the columns la cylindrical, the upper two-thirds being diminished by a conchoidal curve called the entasis, the reduction of the shaft at the neck in all cases being one-sixth of the lower diameter.

In term, of the lower diameter, the Tuscan, Doric, Ionic. Corinthian, and Composite columns are respectively 7, 8, 9, 10, and 10 diameters high.

Table III. Roman Orders

 Title. Index Letter on Fig. 2. Height of Pedestal. Height of Column. Height of Entablature. Altitude of Orders. Base a. Dado b. Cornice c. Total. Base d. Shaft e. Cap f. Total. Arch. g. Frieze h. Cornice i. Total. With Pedestal. Without Pedestal. m P m p m p m P m P m P m P m P m p m P m p m P m P m P Tuscan ...... A 0 15 8 20 0 15 4 20 0 30 12 1 0 0 30 14 0 0 30 1 5 1 10 3 15 22 6 17 15 Doric .......... B 0 25 4 0 0 15 5 10 0 30 14 0 0 30 16 0 0 30 1 15 1 15 1 0 25 10 20 0 Ionic .......... C 0 16 2/3 4 26 2/3 0 16 2/3 6 0 1 2 16 8 0 20 18 0 1 7.5 1 15 1 22 1/2 1 15 28 15 22 15 Corinthian... D 0 25 5 0 0 25 6 20 1 2 1/2 16 17 1/2 2 10 20 0 1 15 1 15 2 0 5 0 81 20 25 0 Composite... E 0 21 2/3 5 3 1/3 0 25 6 20 1 2 1/2 16 17 1/2 2 10 20 0 1 15 1 15 2 0 5 0 81 20 25 0

The Tuscan order is a simplification of the Doric. The proportions of the Doric are less sturdy than those of the Greek prototype and the shaft is often left unfluted. The Ionic order is more enriched than the Greek, and the capital is generally made uniform on all sides by placing the volutes anglewise. The Corinthian order was the favorite of the Romans, and was used in the largest temples. The Composite order was invented by the Romans. The capital, its distinctive feature, is a combination of the Ionic and Corinthian.