He Proportion of the Pillars of the Ionick Order in the beginning had Eight Modules or Diameters for their height, but the Ancients quickly added half a Diameter, when to make this Pillar more Beautiful than the Dorick, not only for its height, but Lib. 4.
Chap. 1. also for its Ornaments, they added a Base to it, which was not used in the Dorick Order.
The Pillars must be set upon their Bases two ways; for sometimes they were perpendicularly set, and sometimes not, viz. The outward rows of Pillars; when there were more Ranks than one; for that part of the Pillar which is towards the Wall of the Fabrick must necessarily be perpendicular, and the outward part must have all the Diminution, and must lean towards the Wall.
Lib. 3.
Chap. 3. The Pillars that are within the porch, and are betwixt the Wall and the outward Pillar must stand perpendicularly.
The breadth of the Ionick Base is the Diameter of the Pillar, to which is added a 4th. and an 8th. part; its height is half the Diameter; its height being divided into three parts, one is allowed for the Plinthus, the rest being divided into seven parts, three are allowed to the Torus above, after equally dividing the four which remain, the two above are for the upper Scotia, with its Astragal: The two below are for the lower Scotia, which will appear greater than the upper, because it extends to the edge of the Plinthus, the Astragals must have the 8th. part of the Scotia, whose Jetting or Projecture must be the 8th. part of the whole Base joyned to the 6th. part of the Diameter of the Pillar. See [Tab. VII.]
As to the Capital, the Abacus must have in its Square the Diameter of the bottom of the Pillar, adding to it an 18th. part; half of the Abacus ought to be the height of the Capital, comprizing the Round of the Volute or Scroll, but there must be substracted from the corner of the Abacus a 12th. part and an half of the height of the Capital, and after the whole thickness of the Capital must be divided into nine parts and an half, and one and an half must be left for the thickness of the Abacus, that the Volutes or Scrolls may be made of the eight which remain; then having left under the Abacus four parts and an half of these eight, a Line must be drawn in the place which cuts the two a-cross and the Points of the Section shall be Eyes, which shall have eight parts for their Diameter; in half the space of the Eye shall be placed the Centers through which shall be drawn with a Compass the Spiral-Line of the Volute, beginning the height under the Abacus, and going into the four Quarters of the Division, diminishing till we come directly to the first Quarter, and giving to every Quarter a particular Center.
Then the thickness of the whole Capital must be so divided that of nine parts which it contains, the Volute has the breadth of three under the Astragal, on the top of the Pillar, which must be directly upon the Eye of the Volute, that which remains above the Astragal, must be allowed for the Abacus, Channel, and the Echine or Egge, whose jetting beyond the Square of the Abacus must be of the same bigness of the Echine or Egge.
The Channel must be hollowed the 12th. part of its breadth.
The Girdle or Cincture, or the lateral part of the Capital, ought to advance out of the Tailhoir Abacus, as much as it is from the Center of the Eye to the height of the Echine.
The thickness of the Axis of the Volutes, which is the thickness of the Volute, seen sideway, and which makes up the extreme parts of that which is called commonly Balisters, ought not to exceed the magnitude of the Eye. See [Tab. VIII.]