The Greeks construct party-walls, resembling those of brickwork, of hard stone or of silex, squared. This kind of stonework is what they call "isodomon,"[1] it being "pseudisodomon"[2] when the wall is built of materials of unequal dimensions. A third kind of stonework is called "emplecton,"[3] the two exteriors only being made with regularity, the rest of the material being thrown in at random. It is necessary that the stones should lie over one another alternately, in such a way that the middle of one stone meets the point of junction of the two below it; and this, too, in the middle of the wall, if possible; but if not, at all events, at the sides. When the middle of the wall is filled up with broken stones, the work is known as "diatoichon."[4]

The reticulated[5] kind of building, which is mostly in use at Rome, is very liable to crack.[6] All building should be done by line and rule, and ought to be strictly on the perpendicular.