230 THE BASIN OF EASTERN PERSIA AND SISTAN. 
THE BASIN REGION OK IRAN. 
Before proceeding to a more detailed study of the influence of an arid climate 
upon the physiography of Eastern Persia, I shall describe the main features of the 
mountain rim and of the diversified basin which it incloses. Among geographical 
writers it is customary- to speak of Persia, Afghanistan, and Baluchistan as composing 
the plateau of Iran. It is well to use the name Iran for the portion of the three 
countries included within the mountain border, but the tenn " plateau " is misleading. 
The region is essentially a basin, not a plateau. From the central knot of the Pamirs, 
a genuine plateau, two mountain passes diverge westward. One, the more northerly, 
runs west by south under the name of Hindu Kush, and then, as the Paropamisus, 
turns directly westward and traverses Northern Afghanistan. From a height of 
25,000 feet in the Pamirs it descends until in Western Afghanistan the highest peaks 
rise but 5,000 or 6,000 feet above the sea, and the main range is traversed from 
south to north by the Heri Rud, the river of Herat. Westward in Persia the 
mountains incline to the north, and in Kopet Dagh and the mountains of Khorasan 
reach an altitude of 10,000 feet. Then, inclining once more to the south, they take 
the name of Elburz, south of the Caspian Sea, and rise to an extreme height of 
19,400 feet in Demavend. Lastly, still at tremendous heights, the range swings to 
the northwest and loses itself in a second mountain knot, the plateau of Armenia. 
The other mountain mass starts from the Pamir as part of the Hindu Kush, but 
soon diverges to the south, and running south-southwest traverses the eastern part 
of Afghanistan and Baluchistan under the name of the Suliman Mountains, rising 
often to heights of 12,000 feet. As it approaches the Arabian Sea it turns west- 
ward, and at decreasing heights follows the seacoast until Persia is reached. Here, 
as in the corresponding portion of the northern range, the mountains are but 5,000 
or 6,000 feet high. F'arther west in Persia, however, the mountains soon regain 
their height, and swinging to the northwest run straight through the center of the 
countrj- at heights from 8,000 to 14,000 feet, and finally in the highlands of Amienia 
coalesce with the northern of the two mountain chains which start from Hindu 
Kush. Between these two chains, and completely inclosed by them, lies the basin 
region of Iran, which is roughly shaped like a segment of a circle, 1,200 miles 
long from east to west, and 600 miles broad. This region, most of which is abso- 
lute desert, contains an area of over 500,000 square miles, and is as large as the 
twenty of the United States which lie east of the Mississippi River and north of 
Tennessee and North Carolina ; or, to compare it with a region where physio- 
graphic conditions are more similar, as large as the five semi-arid states of Colorado, 
Utah, Nevada, Arizona, and New Mexico. 
THE TWO B.\SINS OF IRAN. 
The basin region of Iran contains two chief basins divided into many smaller 
basins (fig. 152). The largest basin, embracing about three-fifths of all Iran, lies 
wholly in Persia and may properly be called the Persian basin. The other chief 
basin, embracing the greater part of the remaining two-fifths of Iran, about 
200,000 square miles, contains parts of Persia, Afghanistan, and Baluchistan. It 
