The mouth may be a simple, circular pore at the extremity of the manubrium, or by folding of the edges it may become square or shaped like a Maltese cross, with four corners and four lips.
Four principal avenues radiate from points near a central circle to the four corners of the city.
At some distance from the shaft a square water-tight wall was built, and the space between it and the shaft was filled in with sand, which was purified of all saline matter by repeated washings; on the ground-level perforated stones set at the four corners of the basin admitted the rain-water, which was discharged from the roofs by lead pipes; this water filtered through the sand and percolated into the shaft of the well, whence it was drawn in copper buckets.
The forms of roof are various, but mostly they commence in a steep slope at the top, gradually flattening towards the eaves so as to produce a slightly concave appearance, this concavity being rendered more emphatic by the tilt which is given to the eaves at the four corners.
Neither the Romans nor the Turks had been able to subdue this square mountainous tract, of which Bougie, Setif, Aumale and Dellys form the four corners.
