"دليل بلاد فارس، المجلد I ويشمل محافظات أستراباد، شاهرود-بوستان، خراسان، وسيستان" [و‎‎٢‎٠‎٣] (٧٢٢/٤١٢)

suddenly widens out to a depth of 250 miles, meeting the watershed of the
Tigris on the one side, and that of the Euphrates and lake Van on the
other, and embracing between the two the basin of lake Urmia or
U runny ah, which is thus completely shut off from the rest of the inward
draining area of Persia, forming, with the basin of lake Van, what may
be termed the supplementary plateau of Armenia, which differs only from
the Persian and Helmand basins in its superior altitude and smaller area.
The basin of lake Grokcha, in the mountains, between the Kur and the
Araxes, might be considered as forming another distinct drainage area ;
but though it has no external outlet, the perfect freshness of its waters
would seem to point, with a probability amounting to conviction, to its hav
ing subterranean communication with one or other of these rivers.
On the east the watershed of the Caspian gradually increases in breadth,
the foot of the scarp extending considerably to the north of the south-east
angle of that sea,, three degrees east cf which it turns to the south-east
parallel to the axis of the Kuran and Kopet ranges, which, as before stated,
are a prolongation of the Caucasus. A short distance south of Herat the
Caspian water-parting turns eastward, separating the valleys of the Hari
Rud and Harut rivers. West of Herat, the desert plateau of Khaf
divides the Caspian from the Helmand basin.
It may be noticed here that the Tajand river, as the united waters
of the Hari Rud and Mashhad rivers are called, does not, as represented
in some recent maps, end in the desert close to Sarakhs, but forms a swamp
in the Atak about the fifty-eighth meridian. Had its water sufficient
volume, they would doubtless find a channel to the Caspian in Haji Bugar
Bay, or to the old bed of the Oxus, between the Lesser Balkhan and the
Kopet range.' As far south as lat. the eastern slopes of the ranges
which shut oil the valley of the Helmand from the deserts or Eastern
Persia drain directly towards the Sistan lake. But south of that parallel
the surplus water flows by several channels in a south-east direction or
away from the lake. About lat. 29° the water-parting of the Baluchis
tan mountain svstem, running east and west, changes the direction of these
streams, and collects them into a single channel, which under the name ot
the Vlashkid river, bursts through the northern scarp of the Baluch hills
into the Kharan desert. Here it takes a noith-westerly course, thus reversing
the original direction of its waters, which are lost in the desert not
far from their most northern sources. It is very probable that they find a
subterranean channel some distance further to the north, and aid to fill the
Zirreh swamp, the southern of the three depressions which, united by flood-
waters, form the Hamun or Sistan lake.
The great central area of Persia, included in the watersheds described
above, forms a figure nearly triangular, with a base running south-west
about 1,000 miles long, and nearly equal sides north and east of 700 miles.
The subdivision of this vast area into different drainage basins will be
treated when we come to describe the hill ranges by which they are
divided.
It will be readily believed that the rainfall on the'Oceanic and Caspian
watershed is far in excess of that on the interior. Wherever the water-
parting is formed, as it is in most parts, by a lofty mountain ridge, it
intercepts the moisture-bearing clouds from the sea, which are discharged
on its outer slopes. The Alburz chain, which shuts off the plateau from