Page 30 - A Hand book of Arabia Vol 1 (iii) Ch 1,2

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€ 16 PHYSICAL SURVEY
of Hejaz, lmlf-way up the Red Sea coast, at or about Lrth, south­

west of Mecca. Prom this point northwards, not only do the >non-
soons cease to discharge, but the average altitude of the uplifted
edge of the land-shelf (here of softer composition) drops some two ,
thousand feet over a stretch of about 300 miles. .Both in the littoial
and inland, therefore, the isolated oasis becomes again the oMly
support of settled life. Between Mecca and Medina, themselves
oasis settlements, there are sparse patches of arable land in hollows
and wadi-bottoms. A hundred miles north of the latter town, any­
thing like a chain of inland oases ends with Kheibar and El- Ala.
As" for the coast, north of Jiddah it is worse* off* for only the
largest wadis bring enough ground-water down to their mouths
to support settlements. In the extreme north, the volcanic system .
«
of eastern Midian raises the tilted edge of the shelf again to a great
elevation ; but its rugged slopes and blistered crests preclude settle­
ments inland ; while the precipitous seaward fall of the secondary
but lofty coastal range has not encouraged settlers. ' *

Climate. f

The atmospheric conditions of the peninsula, except in some
of its littoral districts, are singularly favourable to human life.'
Intense dryness mitigates the heat by day, ensures cool nights,
and, being, apparently, unsuited to much of the germ-life which
preys on humanity, elsewhere, inspires vigour. Given conditions

under which adecpiate nourishment of the body can be obtained, as
in the central oases for example, or on the nefuds and steppes in
spring, human natality is high and the average duration of life is
long. Under other conditions, however, as among those Bedouins
who pass the year round on the leaner steppes, exhaustion comes
early in life. 'This appears to be felt also where—as on the Yemen
plateau, which lies at an elevation of 7,000 to 8,000 ft.—the diurnal
range of temperature is very great—a drawback which impairs the
sanitary value of most tropical hill-stations.
The outstanding feature of the Arabian climate is this dryness.
Arabia is placed between seas . . ., but these are so narrow as
hardly to break climatic continuity with the Asian and African
continental masses, both of which are exceptionally rainless in these
latitudes.’ Yemen profits by the autumnal monsoon, when this is
not diverted, as it seems to be now and then, by the near highlands
of Africa . hut the steep westward face of the Yemen and Asir
massifs causes the moisture-laden current to rise rapidly ahd tborf>
fore.discharge so fully that it retains little 1 * e'
or no precipitation for

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