The Column—The Shaft
The general proportions of the column have already been given. The shaft is invariably tapered for two-thirds of its height, the lower third being cylindrical, and the taper terminates at the necking moulding. In all three orders the difference between the upper and lower diameters is the same, that is, the upper is five-sixths of the lower, but although the amount of taper is numerically the same, the different ratios of the diameters to the heights produce naturally very different results.
The shaft of the Doric column may be plain or channelled with vertical grooves called flutes. There are twenty of these flutes round the circumference. On plan they are shallow, and may be formed of arcs of a third of a circle. The curves meet without intervening fillets. The flutes are finished off in segmental curves at the top and bottom, leaving a small plain space below the necking and above the base.
The Ionic and Corinthian columns may have plain or decorated shafts. If decorated they have twenty-four flutes round the circumference. These are semi-circular on plan, and are spaced with fillets between them.