"دليل بلاد فارس، المجلد I ويشمل محافظات أستراباد، شاهرود-بوستان، خراسان، وسيستان" [ظ‎‎٢‎٠‎٣] (٧٢٢/٤١٣)

face is furrowed "into deep valleys by the constant and heavy showers, which
have clothed them in forests of almost tropical luxuriance ; while the
southern generally presents a single abrupt scarp, rising above long gravel
slopes, unchannelled by anything worthy the name of a river, and bare of
any vegetation rising to the dignity of a tree. At the most moderate
estimate the rainfall of Gilan and Mazandaran may be taken as five times
that of the adjoining districts across the ridges to the south.
In other parts, however, we find the water-parting considerably below
the level of the summits further inland ; and here the interior has a more
plenteous rainfall than the coast. This is particularly the casein south
eastern Persia, where the Khurasan, Sarhad, and Dizak hills, far exceeding
in altitude the ranges to the south, attract to themselves the major portion
of the scanty supply of moisture borne inland from the sea.
Again, the rainfall differs very much in different parts of the country,
under apparently similar conditions as regards mountains and distance
from the sea; the east and south being far drier than the north and west,
while the dampest parts of the Tigris valley have not half the rainfall
of the southern and south-eastern shores of the Caspian.
north-west or south-east. The first cause is the position of the Black Sea
and Mediterranean on the north-west, and of the Arabian Sea on the
south-east. The second is the bearing of the axes of the great mountain
chains, which lie mainly in the same direction north-west and south-east,
and thus tend to guide the currents of air in a uniform course. The
south-west, moreover, is not felt, except as moderating the temperature of
the Makran coast, inside a line from Ras-al-Hadd, south of Maskat, to
Karachi.
The effect of the sun on the great Iranian plateau is to produce a
heated stratum of air ; which, when it rises, is succeeded by a current from
Naturally the latter is the colder, and therefore, as might be expected,
north-west winds are most prevalent. But in southern Persia and the gulf
it often occurs that the two currents meet, and that a north-westetly
gale is raging at Bushahr, while a south-easter is blowing at Bandar
Abbas. This latter wind is the rain-bearer throughout the greater part of
Persia, the exception being the north-west, where occasional rain-clouds
from the Black Sea and the Caspian find their way across the Kurdish
mountains or the Alburz. It is true that it often rains even on che gulf
during a north-wester; but only when this has followed a succession of
south-easterly gales, the moisture borne by which is returned from the
opposite quarter.
In the absence of statistics extending over even a single year (and an
average of fifteen years at least would, I think, be requisite), it is impossi
ble to give more than an opinion as to the amount of rainfall in Persia.
But I believe I am well within the mark in stating that no part of the
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