INTERCOLUMNIATION, OR THE SPACING OF COLUMNS—PLATE XVIII
The space between two columns, measured just above their bases, is called an Inter calumniation. It is one Diameter less than their distance apart on centers, or on edges.
Columns are said to be Coupled, or to have a Pycnostyle, Systyle, Diastyle, or Areostyle Intercolumniation, according as they are set close together, or are one, two, three, or four Diameters apart, as nearly as may be; i. e., about one, two, three, four, or five Diameters on centers. The Systyle and Diastyle are the most usual, with an Intercolumniation of two or of three Diameters.
But Coupled Columns cannot be nearer than one and one-third Diameters, on centers, instead of one Diameter, on account of the projection of their bases, and in the Ionic, Corinthian, and Composite Orders, not nearer than one and one-half Diameters, on account of the projection of their Capitals. The Intercolumniation of Coupled Columns is accordingly one-third or one-half of a Diameter, or even a little more, to prevent the Bases or Caps from actually touching. As this brings them eight-sixths Diameters, or nine-sixths Diameters, on centers, the Ionic and Corinthian dentils, which are one-
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sixth Diameter on centers, come exactly on the axis of the columns. This occurs also -with the dentils of Vignola's Composite Order, which are one-fourth Diameter on centers, since nine-sixths Diameters equals six-fourths Diameters, and there is just room for five dentils over the Intercolumniation. But since the Corinthian Modillions are four-sixths of a Diameter on centers, and the shafts of Coupled Columns are nine-sixths Diameters on centers, it is necessary to widen each of the two caissons between the Modillions by one-twelfth Diameter, and increase the width of the Dentils and Interdentils by one-eighth, making the Dentils one-eighth of a Diameter in width instead of one-ninth, and the Interdentils one-sixteenth of a Diameter instead of one-eighteenth. [19×118=18; 118×118=116.]
So also the Pycnostyle Intercolumniation is made one and one-fourth Diameters instead of one Diameter (i. e., two and one-fourth Diameters on centers, instead of two) to avoid crowding. The ancients thought that even the Systyle columns, with an Intercolumniation of two Diameters, came too near together, and preferred what they called the Eustyle Intercolumniation, of two and one-half Diameters (or three and one-half Diameters on centers, in place of three Diameters). But the moderns prefer to make the Eustyle Intercolumniation two and one-third Diameters (setting the columns three and one-third Diameters, on centers), as this brings every Column in Ionic and Corinthian colonnades exactly under a Dentil, and every alternate one just under a Modillion, the Dentils being one-sixth of a Diameter on centers, and the Modillions two-thirds of a Diameter.
The wider Intercolumniations are preferable, obviously, when the columns are small, since otherwise it might be difficult to get between them, and the Systyle, or even the Pycnostyle, when the columns are very large, since otherwise it might be difficult to find stone architraves long enough to span the interval. But the ancients used Tuscan Columns chiefly with wooden architraves, setting them as much as seven Diameters
