The construction of the walls of the Greek temples rivalled that of the Egyptians in accuracy and beauty of workmanship, and resembled them in the use of solid materials. The Greeks had within reach quarries of marble, the most beautiful material which nature has provided for the use of the builder; and great fineness of surface and high finish were attained. Some interesting examples of hollow walling occur in the construction of the Parthenon. The wall was not an element of the building on which the Greek architect seemed to dwell with pleasure; much of it is almost invariably overshadowed by the lines of columns which form the main features of the building. The pediment (or gable) of a temple is a grand development of the walls, and perhaps the most striking of the additions which the Greeks made to the resources of the architect. It offers a fine field for sculpture, and adds real and apparent height beyond anything that the Egyptians ever attempted since the days of the Pyramid-builders; and it has remained in constant use to the present hour. We do not hear of towers being attached to buildings, and, although such monumental structures as the Mausoleum of Halicarnassus approached the proportions of a tower, height does not seem to have commended itself to the mind of the Greek architect as necessary to the buildings which he designed. It was reserved for Roman and Christian art to introduce this element of architectural effect in all its power. On the other hand, the Greek, like the Persian architect, emphasised the base of his building in a remarkable manner, not only by base mouldings, but by planting the whole structure on a great range of steps which formed an essential part of the composition. _The Roof._ The construction of the roofs of Greek temples has been the subject of much debate. It is almost certain that they were in some way so made as to admit light. They were framed of timber and covered by tiles, often, if not always, of marble. Although all traces of the timber framing have disappeared, we can at least know that the pitch was not steep, by the slope of the outline of the pediments, which formed, as has already been said, perhaps the chief glory of a Greek temple. The flat stone roofs sometimes used by the Egyptians, and necessitating the placing of columns or other supports close together, seem to have become disused, with the exception that where a temple was surrounded by a range of columns the space between the main wall and the columns was so covered. The vaulted stone roofs of the archaic buildings, of which the treasury of Atreus (Figs. 52, 52a) was the type, do not seem to have prevailed in a later period, or, so far as we know, to have been succeeded by any similar covering or vault of a more scientific construction.