Page:Ware - The American Vignola, 1920.djvu/52

42 Upon this is founded the following rule for the slope of Pediments, devised by Stanislas L'Eveillé, Fig. 149: Taking the upper line of the Horizontal Cornice as one side, construct below it an equilateral triangle, and taking the vertex of this triangle as a center, and its side as a radius, describe an arc of 60 degrees. Taking, then, the summit of this arc as a center, describe a circle, the radius of which is equal to the width of the horizontal cornice. Lines drawn from the extremities of the Corona tangent to this circle will give the upper line of the Raking Corona. It is obvious that the larger the cornice, relatively to the length of the front, the steeper will be the slope. It is also plain that this rule gives steeper Pediments for the Corinthian and Ionic Orders than for the Doric and Tuscan, and for the Roman Orders than for the Greek, the cornices being wider.

Circular, or Curved, Pediments have a sweep of 90 degrees, Fig. 150, starting at an angle of 45 degrees.

When Pediments are used merely for ornament the upper part is sometimes omitted, giving a Broken Pediment, Fig. 152.

If the molding that crowns the Corona is omitted, the faces of the three Coronas are continuous, Fig. 151. This was exemplified in Antiquity by the recently discovered Treasury of the Cnidians at Delphi.

In a Raking Cornice the modillions, dentils and egg-and-darts have their axes vertical and in line with those in the Horizontal Cornice beneath. But in the Maison Carrée at Nimes they are set at right angles with the Corona, and this is regularly done with the Eggs-and-Darts where an ovolo occurs alone, without dentils or modillions. It a modillion occurs at the apex of the pediment it is broken. This occurs when the center intercolumniation is Diastyle, with the columns four Diameters, or twelve thirds, on centers, giving five modillions over the opening between them, or with any other spacing which makes their distance on centers a multiple of four-thirds of a Diameter.