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Rh rising north of Teheran, the Kend and Kerej rivers, rising north-west of Teheran, the Shureh-rud (also called Abhar-rud), rising near Sultanieh on the road between Kazvin and Tabriz, and the Kara-su, which rises near Hamadan and is Joined by the Zarin-rud (also known as Do-ab), the Reza Chai (also called Mazdakan-rud), the Jehrud River and the Kum-rud. The river of Isfahan, Zendeh-rud, i.e. “the great river” (from Persian zendeh [Pehlevi, zendek], great), but now generally known as Zayendeh-rud, i.e. “the life-giving river,” flows into the Gavkhani or Gavkhaneh swamp, east of Isfahan. In Fars the Kur with its affluents forms the lake of Bakhtegan (also known as Lake of Niriz), and in its lower course, is generally called Bandamir (made famous by Thomas Moore) from the band (dam) constructed by the Amir (prince) Asad-ed-dowleh in the 10th century. (“Note on the Kur River in Fars,” Proc. Royal Geog. Soc., London, 1891.) The rivers flowing into the Persian Gulf and Arabian Sea diminish in importance from west to east. There are first the Diyala and Kerkheh flowing into the Tigris from the hills of Kurdistan; the Ab i Diz and Karun which unite below Shushter, and reach the Shatt el Arab at Muhamrah; and the Jarahi and Tab, which with the Karun form “the delta of Persian Arabistan, the most extensive and fertile plain in Persia.” There are many streams which though fordable at most seasons (some of them are often quite dry) are unfordable during the rains. Two of these may be mentioned here, viz. the Mand and the Minab, which St John (loc. cit. p. 9) considered as being “of far more importance than the maps would lead the observer to suppose.” The former, after a run of over 300 m. from its sources in the hills west of Shiraz, debouches at Khor-i-Ziaret about 60 m. south of Bushire. It is mentioned by the old Arab and Persian geographers as the Sitakan (in some MSS. misspelt Sakkan), and is the Sitakos of Airian and the Sitioganus of Pliny. In its upper course it is now known as the Kara-aghach (Wych-elm) River (cf. “Notes on the River Mand in Southern Persia,” Royal Geog. Soc., London, December 1883). The Minab has two outlets into the Persian Gulf, one the Khor-i-Minab, a salt-water creek into which the river overflows during the rains, about 30 m. east of Bander Abbasi, the other the true Minab, at Khagun, some miles south of the creek. It rises in the hills about 100 m. north of Bander Abbasi, and has a considerable drainage. Its bed near the town of Minab (15 m. from the coast) is nearly a mile in width, and during the rains the water covers the whole bed, rendering it quite unfordable. During ordinary weather, in March 1884, the water flowing past the town was 100 yds. in width and 2 ft. deep (Preece, Proc. Royal Geog. Soc., January 1885). In ordinary seasons very little water of the river runs into its original bed, being diverted into canals, &c. The creek, the Anamis of Nearchus, is navigable nearly all through the year as far as Shahbander, the custom-house, about 7 m. inland, for vessels of 20 tons burden.

“The great desert region of Persia,” writes Le Strange (Lands of the Eastern Caliphate, 1905), “stretches right across the high plateau of Irân going from north-west to south-east, and dividing the fertile provinces of the land into two groups; for the desert is continuous from the southern base of the Elburz mountains, that to the north overlook the Caspian, to the arid ranges of Makrân, which border the Persian Gulf. Thus it measures nearly 800 m. in length, but the breadth varies considerably; for in shape this immense area of drought is somewhat that of an hour-glass with a narrow neck, measuring only some 100 m. across, dividing Kermân from Seistân, while both north and south of this the breadth expands and in places reaches to over 200 m. At the present day the desert, as a whole, is known as the Lût or Dasht-i-Lût; the saline swamps and the dry salt area being more particularly known as the Dasht-i-Kavîr, the term Kavîr being also occasionally applied to the desert as a whole.”

A three-wire telegraph line on iron posts, completed in March 1907, passes through this region, and it is the unenviable lot of some Englishmen stationed at Bam and Nusretabad Ispi (Isbidh of medieval Arab geographers) on the confines of the desert regularly to inspect and test it. Of the northerly Great Kavir Dr Tietze thought that it was composed of a complex of isolated salt swamps separated by sand-dunes, low ridges of limestone and gypsum, perhaps also by volcanic rocks (Jahrbuch k. k. geolog. Reichsanstalt, Vienna, 1877). Dr Sven Hedin explored the northern part of the Great Desert in 1906.

Geology.—Persia consists of a central region covered by Quaternary deposits and bordered on the north, west and south by a raised rim composed of older rocks. These older rocks also form the isolated ranges which rise through the Quaternary deposits of the central area.

In northern Persia the rocks of the elevated rim are thrown into folds which form a curve round the southern shore of the Caspian. The mountain ranges of Khorasan show the western portion of a second curve of folding which is probably continued into the Hindu Kush. In the western rim of Persia the folds run from north-west to south-east, and in the south these folds appear to curve gradually eastward, following the trend of the coast. The folds in the central Persian chains run from north-west to south-east, parallel to those of the western border. It is seldom that the old crystalline rocks, which form the floor upon which the sedimentary strata were

deposited, are exposed to view. Gneiss, granite and crystalline schist, however, are found in the Elburz and in some of the central ranges; and similar rocks form a large part of the Zagros. Some of these rocks are probably Archean, but some appear to be metamorphosed sedimentary deposits of later date. The oldest beds in which fossils have yet been found belong to the Upper Devonian. They are well developed in the Elburz range, where they attain a thickness of some 9000 to 10,000 ft., and they have been found also in some of the central ranges and in the Bakhtiari Mountains. In the Elburz range the Devonian is succeeded by a series of limestones with Productus. The greater part of the series belongs to the Carboniferous, but the upper beds are probably of Permian age. The limestones are followed by sandstones and shales with occasional seams of coal. The plants which have been found in these beds indicate a Rhaetic or Liassic age. The Middle and Upper Jurassic form a considerable portion of the Elburz and have yielded marine fossils belonging to several different horizons. The Cretaceous system is very widely spread in Persia. It is one of the most conspicuous formations in the Zagros and in the central ranges, and probably forms a large part of the plateau, beneath the Quaternary deposits. The most prominent member of the series is a massive limestone containing Hippurites and belonging to the upper division of the system. The Tertiary deposits include nummulitic limestone (Eocene); a series of limestones, sandstones and conglomerates, with marine Miocene fossils; and red marls, clays and sandstones with rock-salt and gypsum, believed to belong to the Upper Miocene. In the Elburz there is a considerable deposit of palagonite tuff which appears to be of Oligocene age. The nummulitic limestone takes part in the formation of the mountain chains. The Miocene deposits generally lie at the foot of the chains, or in the valleys; but occasionally they are found at higher levels. Pliocene deposits cover a considerable area near the coast. Both in the Elburz range and near the Baluchistan frontier there are numerous recent volcanoes. Some of these seem to be extinct, but several continue to emit vapours and gases. Demavend in the Elburz and Kuh-i-Taftan on the Baluchistan frontier are among the best-known.

See W. K. Loftus, “On the Geology of Portions of the Turko-Persian Frontier, and of the Districts adjoining,” ''Quart. Journ.'' ''Geol. Soc.'' vol. xi. pp. 247-344, pl. ix. (London, 1855); W. T. Blanford, Eastern Persia, vol. ii. (Zoology and Geology) (London, 1876); C. L. Griesbach, Field-notes: No. 5, to accompany a Geological Sketch Map of Afghanistan and North-Eastern Khorasan, Rec. Geol. Surv. India, xx. 93–103 (1887), with map; A. F. Stahl, “Zur Geologie von Persien,” ''Peterm. Mitt., Ergänzungsheft 122 (1897); J. de Morgan, Mission scientifique en Perse'', vol. iii. (completed 1905, Paris). A summary by H. Douvillé of the principal geological results of de Morgan’s expedition will be found in ''Bull. soc. géol. France'', 4th series, vol. iv. pp. 539-553.

Climate.—For the rainfal on the watershed of the Persian Gulf there are two places of observation, Bushire and Jask; at the first it is a little in excess of that of inner Persia, while at the second it is very much less. The rainfall on the Caspian watershed greatly exceeds that of inner Persia; at Astarabad and Ashurada, in the south-eastern corner of the Caspian, it is about 50% more; and at Resht and Lenkoran, in the south-western corner, it is four and five times that of the adjoining districts across the ridges to the south. With the exception of the Caspian watershed and that of the Urmia basin, the country has probably in no part a yearly rainfall exceeding 13 or 14 in., and throughout the greater part of central and south-eastern Persia the yearly rainfall probably does not exceed 6 in. The following mean values of the rainfall at Teherān have been derived from observations taken by the writer during 1892–1907:— Good harvests depend on the rainfall from October to April, and on an amount of snow sufficient to cover the crops during frosts. During normal winters in Teherān and surrounding districts the rainfall amounts to 9 or 10 in., with 3 to 4 of snow, but in the winter 1898–1899 it was only 5 in, with only 1 in. of snow; and in 1899–1900 the harvests were in consequence exceptionally bad, and large quantities of wheat and flour had to be brought from the provinces and even from Russia at high freights, causing the price of bread at Teherān to rise 200%. The first table on p. 191 shows the mean annual rainfall in inches at fifteen stations in and near Persia.

The prevailing winds throughout Persia and the Persian Gulf are the north-west and south-east owing partly to the position of the Black Sea and Mediterranean and of the Arabian Sea, and partly