Farther south, towards Lake Balkash, on the southeastern frontier, is a wide waterless desert, Bek-pak-dala, or Famine Steppe.
From the wells of Shakik he crossed the waterless Nafud in four days to Jubba, and after a halt there in the nomad camps, he moved on to Hail, already a thriving town, and the capital of the Shammar state whose limits included all northern Arabia from Kasim to the Syrian border.
Of those who essayed to cross the waterless Haud more than one lost his life.
On the 10th the force left the Nile at Duem and struck inland across the almost waterless wastes of Kordofan for Obeid.
South of the Golis the ground falls gradually to the central plateau known as the Haud, a waterless but not unfertile district.
South of the divide the level at once drops to the central depression of Gobi, which forms a vast interior, almost waterless space, where the local drainage is lost in deserts or swamps.
The karez is a system of underground channelling which usually taps a sub-surface water supply at the foot of some of the many rugged and apparently waterless hills which cover the face of the country.
So that for an hour or more, a thousand fathoms in the sea, he carries a surplus stock of vitality in him, just as the camel crossing the waterless desert carries a surplus supply of drink for future use in its four supplementary stomachs.
The country consists chiefly of slightly elevated arid plains, largely waterless save along the southern frontier.
The migrations must have always been dependent upon physical difficulties, such as waterless tracts or mountain barriers.