[682] Three have been identified--Giaur Kal`a, Sultan Sanjar, and Bahrām `Alī. Some entrenchments are fabled to represent a fourth, older than the rest, built by Alexander the Great. But, as is well known, Iskandar Zū-l-Karnayn, “Alexander the Two-horned,” shares with Tīmūr and the Amīr `Abdullah the credit of having built nearly everything worth seeing in Central Asia. [683] Moore’s _Veiled Prophet of Khorasan_. [684] A description of the difficulties encountered has already been given. [685] Khanikoff’s _Bokhara_, p. 18; _Journal of the Royal Geographical Society_, 8th June 1840. [686] “Mémoire sur l’ancien cours de l’Oxus,” par M. Jaubert, _Nouveau Journal Asiatique_, Dec. 1833. [687] Ney, _En Asie Centrale_, p. 300. [688] The Zarafshān, called by the ancients Polytimætus, takes its rise in a tremendous glacier of the Kharlatau Mountains, 270 miles due east of Samarkand. Its upper reaches are little but a succession of cataracts, and it is too rapid and shallow for navigation. The average width is 210 feet. More than 100 canals are supplied by this source of Bokhārā’s prosperity, some of which are 140 feet broad. The capital is watered by one of them, called the Shari Rūd, which is 35 feet wide, and supplies innumerable smaller distributories (Khanikoff’s _Bokhara_, p. 39; Meyendorff’s _Bokhara_ (Paris, 1820), p. 148). [689] Moser, _A Travers l’Asie Centrale_, p. 120. [690] Khanikoff, p. 188. [691] Throughout Central Asia the unit of surface measure is the tanap, which is equivalent to 44,100 square feet. This pest is termed reh in India, and is fought in a very half-hearted way by the ryots. [692] Khanikoff, _Bokhara_, p. 9. This author, who wrote in 1845, gives as the average price of good land a sum equivalent to £20 of our currency (p. 154). Forty years later the Russians paid £16 per acre for land required for their railway (Ney, _En Asie Centrale_, p. 311). [693] According to Wolff, it numbered 180,000 in 1843 (_Bokhara_, p. 163). [694] They are named Imām, Samarkand, Mazār, Kārshi, Salahkhānā, Namāziyya, Shaykh Jalāl, Kārākul, Shīr-Gīrān, Talipash, and Oghlān. [695] For the ethnology of Bokhārā the reader should consult Meyendorff, p. 189; Khanikoff, chaps. vii., viii., and ix.; and Moser, _A Travers l’Asie Centrale_, p. 68. [696] The etymology of Bokhārā is also a moot point. There can be little doubt, however, that the word is derived from the Sanskrit _vihára_, or hermit-cell, which was adopted by the Buddhists and became _búhára_ in Mongolian. The city clustered round the retreat of an early ascetic.