SUPERPOSITION PLATE—XVIII
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Superposition is the placing of one Order above another, as in the Roman Amphitheaters and in many modern buildings of several stories. The more solid forms of the Tuscan and Doric are naturally placed below, and the Ionic and Corinthian above. The Composite is sometimes placed below the Corinthian, as being more vigorous. But in high buildings it is generally placed on the top story, its large details being better seen at a distance than are those of the more delicate Order.
Even when the same Order is employed in the different stories it is advisable to have the upper Columns of smaller diameter than those below, and all the dimensions diminished accordingly, for the sake of lightness. But it is still more so when different Orders are superposed, for otherwise the Doric and Corinthian stories would overpower the Tuscan and Ionic ones beneath (Plate XVIII, A). It is usual, accordingly, to make the lower diameter of each Shaft equal to the upper diameter of the Shaft below it, as if they were all cut from a single piece of tapering stone (Plate XVIII, B). This makes the scale employed in the second story five-sixths of that used in the first; in the third, twenty-five thirty-sixths, or about two-thirds; in the fourth, about three-fifths, and in the fifth, about one-half, if the Five Orders are employed in regular sequence; this makes the relative height of the Orders in the successive stories to be as 7, 623 , 614, 556, and 5, very nearly. The actual height of the stories themselves may be somewhat modified by the use of plinths and pedestals.
This system of Superposition makes the distance apart of the Columns in each story, when expressed in terms of their own Diameter, six-fifths of that in the story below. A Eustyle Intercolumniation in one story thus exactly produces a Diastyle Intercolumniation in the story above, and a Doric Monotriglyph Intercolumniation, a Systyle (Plate XVIII, F).
(65×312 = 4; 65×212 = 3)
Coupled Columns set one and one-third Diameters apart, on centers, in one story, are, in the story above, one and three-fifths Diameters o. c., and in the third story nearly two Diameters o. c. This does very well for
