The string course should never exceed in height that of a rustic with its joints; nor should the socic, or plinth, be less than that of the string course. When the string course is a cornice, the base may be moulded; in such cases, the cornice may be about an eighteenth part of the height of the basement, and its projection about two-thirds of its own height, so as to be less prominent than that with which the building is crowned. The base may be twice the height of the cornice, and being divided into six parts, the lower five may form the plinth, and the remainder be occupied by the mould ings.
When the basement is perforated with arcades, the imposts of the arches may be a platband, equal in height to that of a rustic without its joint.
Pedeatala are used for supporting a colonnade or a pi lastrade ; and sometimes they supply the office of a base ment to a building. They consist of a base, surmounted with a rectangular prismatic solid, called the die, crown ed with a cornice.
The use of pedestals appears to have been an innova tion subsequent to the loss of political independence in Greece. In the original examples of Grecian architec ture, we find the columns standing on the uppermost of three steps; a rule, to which we know of but one exist ing exception, to be seen in the temple of Theseus at Athens, which has but two steps. The Romans, how ever, when they raised the floors of their temples and other edifices high, were under the necessity of discon tinuing the front stairs, lest they should prove inconve nient by occupying too much ground around the budd ing, and of adopting the pedestal or podium, raised to a level with the top of the stairs, and projecting to the front of the steps which profiled on its sides.
Vitruvius, in treating of the Doric, Tuscan, and Co rinthian orders, makes no mention of a pedestal; and, in treating of the Ionic, speaks of it as a necessary part of the construction, but not as part of the order.
Wherever pedestals are introduced, the grandeur of the order is diminished, as all the parts arc proportion ally reduced; yet are they indispensible in some situa tions, as in the interior of modern churches, where, with out them, the beauty of the columns would be lost, through so large a portion of them being hidden by the enclosures of the pews.
In ancient Roman buildings, the proportions of pe destals are very variable; but some modern writers have endeavoured to reduce them to a regular standard. Vig nola would have them to be one-third of the altitude of the column; but as this appeared to make them too high, Sir William Chambers reduced it to three-tenths ; but both ratios must be subject to variation, according to circumstances : Pedestals still lower are to be pre ferred.
The parts of pedestals may have the following pro portions, which may- be considered as common to all Divide the wil& height into nine equal parts, and give two to the base, six to the die, and one to the cornice.
The base may be subdivided into three paits, of which the plinth may have two, and the mouldings one, which 3 nay in general have a projection equal to their height. The plan of the die must be similar to that of the plinth of the column; and the projection of the cornice may be equal to its height.
As to the decorations of pedestals, projecting tablets are inadmissible. It is sometimes customary to adorn the dies with sunk pannels, surrounded with mouldings; and the pannels themselves are occasionally occupied by bas-reliefs or inscriptions. The dies of the pedestals in the arches of Septimins Sev-erus, and of Constantine, have straight-headed niches, containing statues.
Pedestals should never be insulated, though the co lumns sustained by them be so. In the ancient theatres and amphitheatres, the inferior orders rested on steps, while all the superior orders stood upon pedestals, which formed a parapet for raising the base of the order suffi ciently high as to be seen on a near approach to the building, and for the spectators to lean over ; but they never exceeded the height necessary for the prevention of accident.
When pedestals were continued with breaks under the columns, or pilasters, in ancient buildings, the breaks were termed stylobatx, and the recess between every two stylohatT, the podium; and both had the same parts disposed at the same levels.
Pcdiments.—These ornaments probably owe their ori gin to the inclined roofs of the primitive huts. They consist of a horizontal cornice, representing a tie-beam, and two others of equal inclination over it, indicative of rafters, or the latter are exchanged for an arched one. The surface included within these cornices is called a tympanum; which, of course, is either a triangle or the segment of a circle. This definition does not include all those species of pediments which have been intro duced, perhaps with more fancy than genuine taste, into modern buildings, but only those of the ancients, who, in most things, were close imitators of the prototypes from which they borrowed their designs. In the true pediment, therefore, we only see a representation of the end of a roof ivhose purpose was to discharge the rain from the ‘-entre of the building, by leading down to the extremi ties, there to be discharged over the flanks, and not over the front, as must be the case in every ligure that can be introduced, except those of a polygonal form, which present their interior angles to the horizontal cornice, or upwards to those of the exterior.