The whole structure of the place is quite different from that of an English building. Except for enclosing a rough garden the Persian builder hardly ever makes a blank wall. Sometimes the walls of the compound, generally the walls of stables and outhouses, but always the sides of rooms, passages, and porticos consist of a series of arches more or less carefully moulded. In the house, unless they are intended for doors, windows, or cupboards, these arched recesses are filled in to a height of three feet; so that round every Persian room there is a series of ledges, called _tāqchas_, about the size of a small mantelpiece, generally a span deep, but sometimes very much deeper, and running in instead of running out. If the height of the room will allow it, there is a line of straight moulding above these arches, and above that a second row, usually much shorter than the lower ones. Above that comes a second series of lines of straight moulding, shelving into the arch of the roof, for the ceilings are always constructed on the arch principle, although they are sometimes flattened on the top when it is intended to build an upper room. These arches are built of brick and mud only, without any wood or wooden foundation; and indeed no wood is used in a Yezd house at all, except for doors and windows. You will find three styles of wall in Persian houses. Sometimes the rough mud is coated over with a smoother surface, either clay and chopped straw, or clay and sand, and the brown colour is left unchanged. In fairly good houses this style is often thought good enough for the summer portico. Very often the angles of the mouldings are pointed with white gypsum, and when ornamental designs in the same fashion are added, the effect is exceedingly pretty. But generally the living rooms in a Persian house are entirely whitened with gypsum, and a moulded design, about an eighth of an inch thick, is made in the centre of the ceiling. These complicated and accurate geometrical designs are produced by the natives with no better tools than a chisel and a bit of string. The formation of the arches and straight mouldings without instruments is equally wonderful, but though the appearance is geometrical two arches never exactly correspond with one another if one comes to measure. Still the construction of a Persian room, perhaps with a large dome, without any better materials than clay, gypsum, and a small modicum of baked brick, without any scaffolding or wooden basis, and with the help of none but the very simplest tools, is a thing that may be accounted one of the most extraordinary marvels of the East.