Page 6 - A Hand book of Arabia Vol 1 (iii) Ch 4,5

<)S H EJAZ

In the rest of Hejaz, where the general elevation is lower and the
gradients are more gentle, these jium.aras become less frequent and
more beneficent. The most important of them, the Wadi Hamdh,
which debouches a few miles S. of Wejh, unites two main channels
from the Ridge, one draining the Kheibar harrah, the other the
‘Aweiriclh harrah. The first gives Medina its underground waters
and extensive suburban oasis ; the second supplies the pal'm-groves
of El-‘Ala. Other waclis of considerable size debouch near Umlejh,
Yambo‘, Rabugh, Qadhimah, Jiddah, and Lith, accounting for
isolated patches of oasis not only at those points on the coast, but
also in both the inner Tihamah and the third zone, between Medina
and Mecca. Oases in the latter zone, however, seldom contain more
than one or two permanent habitations, being owned by tribesmen
of the surrounding steppes. The valleys of the squthern wadis
do not affect communications ■ so adversely as in Midiah. Indeed
the westward course of' Wacli Hamdh from Medina, and the con­

fluence there of a tributary from the south, have facilitated the
pilgrim route towards Mecca ; and the others all assist communi-
cation’from the coast, e.g. between Yambo‘ and Medina ; between
Rabugh or Jiddah and Mecca ; and between Lith and Ta’if.
The principal superficial characteristic of Hejaz is general barren­
ness, relieved only in the first and third zones by rare oases. The
littoral zone, except at wadi-mouths, is throughout coralline rock
and dusty sand ; the hills of the second zone are of dusty surface
where not naked limestone ; the third zone is steppe verging on
nefud desert ; the fourth is rocky in the northern part, and
frequently harrah desert; the fifth is stony steppe, softening in
the north to sheer nefud.

B. Climate

It hardly needs to be stated, therefore, that precipitation is
insufficient throughout Hejaz. The Midian highlands get a little
more than the Egyptian Delta ; the rest of Hejaz a little more
than middle Egypt. Except at Ta’if in the extreme south, there
are no seasonal rains as in Asir and Yemen. In Mecca precipitation
occurs, chiefly in summer, during brief thunderstorms, and water
flows down the surface of Hejazi fiumaras only at very rare
intervals, though sometimes in great volume for a clay or two.

The climate of the Hejaz lowland is little better than that
°f the Yemen Tihamah, the mean annual temperature being