2If the width be greater than forty feet, columns opposite to those which are between the antæ, are placed towards the inner part, of the same height as those in front, but their thickness is to be diminished as follows. If those in front are an eighth part of their height in thickness, these are to be one ninth; and if the former are a ninth, or a tenth, the latter are to be proportionally diminished. For where the air does not play round them, the diminution thus made will not be perceived; lest, however, they should appear slenderer, when the flutes of the external columns be twenty-four in number, these may have twenty-eight, or even thirty-two. Thus, what is taken from the absolute mass of the shaft, will be imperceptibly aided by the number of the flutes, and though of different thicknesses, they will have the appearance of being equal.
2If the width is to be more than forty feet, let columns be placed inside and opposite to the columns between the antae. They should have the same height as the columns in front of them, but their thickness should be proportionately reduced: thus, if the columns in front are in thickness one eighth of their height, these should be one tenth; if the former are one ninth or one tenth, these should be reduced in the same proportion. For their reduction will not be discernible, as the air has not free play about them. Still, in case they look too slender, when the outer columns have twenty or twenty-four flutes, these may have twenty-eight or thirty-two. Thus the additional number of flutes will make up proportionately for the loss in the body of the shaft, preventing it from being seen, and so in a different way the columns will be made to look equally thick.