tif it is desert and only inhabited by nomads; at
Katif, however, and throughout the district to the south bordering on
the Gulf of Bahrein there are ample supplies of underground water,
welling up in abundant springs often at a high temperature, and
bringing fertility to an extensive district of which El Hofuf, a town
of 15,000 to 20,000 inhabitants, is the most important centre.

South-western Arabia.

South-western Arabia, from the twenty-first parallel down to the Gulf
of Aden, including the Taif district of Hejaz, Asir and Yemen, forms
one province geographically. Throughout its length it consists of
three zones, a narrow coastal strip, rarely exceeding 20 m. in width,
a central mountainous tract, embracing the great chain which runs
parallel to the coast from near Taif to within 50 m. of Aden, and an
inner plateau falling gradually to the north-east till it merges in
the Nejd steppes or the sands of the great desert.

The lowland strip or Tehama consists partly of a gravelly plain, the
_Khabt_, covered sparsely with acacia and other desert shrubs and
trees, and furnishing pasturage for large flocks of goats and camels;
and partly of sterile wastes of sand like the _Ramla_, which extends
on either side of Aden almost from the seashore to the foot of the
hills. The Tehama is, however, by no means all desert, the mountain
torrents where they debouch into the plain have formed considerable
tracts of alluvial soil of the highest degree of fertility producing
in that warm equable climate two and even three crops in the year. The
flood-water is controlled by a system of dams and channels constructed
so as to utilize every drop, and the extent of cultivation is limited
more by the supply of water available than by the amount of suitable
soil. These districts support a large settled population and several
considerable towns, of which Bet el Fakih and Zubed in the western and
Lahej in the southern Tehama, with 4000 to 6000 inhabitants, are the
most important. There are signs that this coastal strip was until a
geologically recent period below sea-level; and that the coast-line is
still receding is evidenced by the history of the town of Muza, once a
flourishing port, now 20 m. inland; while Bet el Fakih and Zubed, once
important centres of the coffee trade, have lost their position
through the silting up of the ports which formerly served them.