But their true province is far removed from towns. Anywhere, where there is scattered grazing and water, one may expect to find the Tuareg nomad of the Sahara, provided that place is remote enough. His home is under the blue sky, and the tiny grass or tent-covered huts of his family are secreted far from the society of other people. Occasionally he may voyage to a trade centre, like a ship seeking a foreign port, to obtain food and clothing and luxuries for his tribe, and glean news of the world beyond his narrow confines; but essentially he is a creature of the wilderness. Their encampments are usually widely scattered: half a dozen huts where the head of the family is located, then a few other families, perhaps miles apart. It is the economic necessity to be within reach of grazing for their live-stock that causes this isolated method of camping. Sometimes food is so very scarce that a single family is the sole occupant of a wide area. These nomadic camps are within reach of water, but, as a general rule, never beside it. That would be dangerous, for water is the calling point of strangers. Camped wide of water, the nomads have a chance to be warned if enemy should arrive in quest to slake their thirst. And this is a fine protective precaution, for the raiders must have water at some place or other during their secretive marches, and forewarning of their presence is often gained in this way; for, even if robbers get in at night to a well-head or water-hole, they cannot cover their tracks in the tell-tale sand. Wherefore, enhancing the strategic position of people who desire to watch and yet not be seen, the dwarf hutments of the encampments are usually in some concealed place: a hollow, or valley, or hill cleft, under shelter of acacias, if such shade is available. Moreover, these places are chosen, if possible, with an eye to a line of retreat in event of an attack. Proximity to low, bouldered hills is favourite ground, or a string of dry river gullies, or, if nothing better offers, a low hollow among deep, billowed sand-dunes.