Cylindroidal columns are those whose sections are all similar and equal ellipses, alike situated. These are other wise called elliptic columns. Instances of this form are rarely to be not with in the remains of antignity ; a few examples, of modern date, are to be seen at Rome.
Polygonal columns have the horizontal sections of their shafts similar to polygons, alike. situated. The lower parts of the shafts of the columns of the portico on the Island of Delos and of the temple of Cora, are of this form ; as are likewise the columns or several Egyptian buildings.
4. Gdumns, according to the decorations of their shafts, are cabled, carolytic, flutul, or twisted.
41 bark-Arnzed column represents the trunk of a tree, with the bark and knots. This is otherwise denominated a pas toral column.
Cabled or rudented columns have the flutings of the shaft tilled with astragals, to about one-third of their height.
Carolytic columns have foliated shafts, decorated with leaves and branches winding spirally- around them, or dis posed in form of crowns and festoons. They were used by the ancients for supporting statues, whence the name. They are suitable in theatres, triumphal arches, &c.
Fluted columns have flutes cut in their sides, in planes passing through their axes, and are otherwise called chan neled to striated columns.
Twisted columns make several circumvolutions in the height of the shaft, after the manner of a screw, and have sometimes several threads or screws following one another in the same circumference ; they are otherwise called spiral columns. Vignola is said to be the first who discovered the method of drawing this kind of column by rule ; but what has been presented to us by this author, is only an incorrect method of drawing the contour of the column on paper, by segments of circles, diminishing in altitude as they become more elevated in their regular succession : but the true principles of forming the shaft ought to be shown from the principles of the spiral, and described upon the colloidal surthce. The barbarous practice of twisting columns has been much used by modern architects, particularly in the screens and altar-pieces of churches. The most celebrated
example is the baldachin of St. Peter's.
Columns spirally formed may be seen in the temple of Spoleto, and are not unfrequent in sarcophagi and other orna mental works.
5. Columns, according to their disposition, are angular, can toned, coupled, doubled, engaged, flanked, grouped, inserted, insulated, median, or niched.
Angular columns are insulated in the corners of a portico, or upon the corners of a building, (even though attached) whether the angle be right, acute, or obtuse.
Cantoned columns are placed one at each corner of a square pier, for supporting the angular springings of groins, or inter-ecting vaults.
Coupled columns are disposed in pairs, in the same range or line, so as almost to touch at their bases; as those in the western portico of St. Paul's, and the peristyle of the Louvre.
Doubled columns, in any range of columns, or in peri styles, seem to have their shafts penetrating each other to about one-third of their diameter ; as in the peristyle of the Lou v re.
Engaged columns seem to penetrate a wall from between one-tburth to one-half of their diameter.
A flanked column has a semi-pilaster on each side of it, and is engaged from one-fourth to one-half its diameter, within the plane of the faces of the semi-pilasters.
Grouped columns stand in threes or fours on the same pedestal.
An inserted column is let into a wall.
An insulated column is free or detached on all sides.
Median columns are those two columns of a portico, which are placed in the middle of the range, at a wider interval than any other two of the same range, for giving a freer access to the principal entrance. The term is derived from columnce media', the name given by Vitruvius to the two columns m the middle of the colonnade.
A niched column is placed in a niche, with the axis of the column in the plane of the wall.
6. Columns, according to their destination, are agricultural, astronomical, boundary or limetrophus, chronological, fu-nerol, gnomonic, historical, indicative, itinerary, lactary, etanubiary, menian, miliary, phosphorical, rostral, statuary, symbolical, or zoophoric.