As the afternoon draws on, flocks of goats can be seen wandering slowly in from the barren hills. They have a public shepherd, paid for by the town, who is responsible for the animals up to the gate of the city; at this point he leaves them and the goats, separating themselves, go independently up the narrow streets to their respective homes. When they reach the door they butt it with their heads or tap with their hoofs until they are let in. The doors of the houses in the Mzab, and especially the locks, are very curious. The door itself is usually made of heavy planks studded with nails and closed with a lock usually associated with a prison gate. This, however, is a modern institution, for the native key is unique in the world. It consists of a piece of wood about a foot long, at the end of which is arranged a pattern of nails. This piece of wood is pushed into a kind of deep slot running from the doorpost diagonally toward the door. From the wall and running into the door is a wooden bar or bolt on which is a pattern of nails corresponding to those on the wooden key. The proprietor slips in his piece of wood until its nails coincide with those inside and then he pulls, the bar gives and it is possible to open the door. It is, I suppose, the origin of the latch-key, as no two combinations of nails are the same, and it means absolute safety to the designer of the piece of wood. At each turn the traveler is experiencing something new, and though he has seen a series of strange customs common to all the cities of the Mzab, the most curious, which is peculiar only to Beni Sgen, has been left to the last. For some reason, which at present it has been impossible to fathom, there are practically no shops in the holy city, and everything is sold by auction. This sounds quite incredible until, climbing down the steep streets, one comes suddenly into a triangular “square” about fifty yards long. At one end on a raised platform sits the _caïd_, surrounded by his counselors, while all around squat men of venerable countenance dressed in white robes.