The stone stylobate at the Heraion was a necessity because of the destructive effect of the moist earth on terracotta; it consisted of a row of vertical slabs on which the bricks were placed in regular courses. We may see in this method of construction the forerunner of the system, universal since that time, of building walls on a plinth, which survives even to the present day. In the same way door-jambs and lintels, which were of necessity made of wood, not of brick, continued to be constructed in that material even after the introduction of stone.[315] It has been assumed by some authorities that the Doric style of architecture is derived from a wooden prototype; this, however true of the Ionic style, is not altogether true of Doric. The proportions of the latter are too heavy. A more probable explanation is that it is the combination of wood with sun-dried tiles or bricks which we see in the Heraion that developed with the introduction of stone into the Doric system.[316] It is then clear that although in Greece bricks were by no means indispensable for building temples, houses, and walls, and though stone and marble undoubtedly had the preference, especially in later times, yet their use is more general than was hitherto supposed. But when they are mentioned by classical authors it is generally when speaking of foreign or barbarian edifices, such as the palace of Kroisos at Sardis or the monument of Hephaestion at Babylon,[317] and in a manner which shows that they were not much employed in Greece at the time when they wrote. The older temple of Apollo at Megara is described by Pausanias[318] as having been of brick (πλίνθος), but we are left in doubt as to whether this was baked or sun-dried; while the excavations at Olympia have distinctly contradicted his statement[319] that the Philippeion was of brick, as it is proved to have been built of stone ashlar.[320] In 333–329 B.C. the Long Walls of Athens were constructed, partly in brick, under Habron, son of Lykourgos, with Laconian tiles for the roofs.[321] Other recorded buildings are all of late date and under Roman influence, and we must leave an account of Roman brick-building to be dealt with in a later chapter (XIX.). There is an interesting passage in the _Birds_ of Aristophanes, in which he is describing the building of the city of Nephelokokkygia, the walls of which are apparently conceived as being of sun-dried brick. He there speaks of “Egyptian brick-bearers,”[322] implying that the use of brick was a characteristic distinction of that nation. The passage (1133–51) is worth quoting in full, as showing the process employed in the making of sun-dried bricks.