The Oxus rises from an Alpine lake, lying on the western side of the Bolor chain in lat. 37 deg. 40’, long. 73 deg. 50’.  After a rapid descent from the high elevation of the lake, during which it pursues a somewhat serpentine course, it debouches from the hills upon the plain about long. 69 deg. 20’, after receiving the river of Fyzabad, and then proceeds, first west and afterwards north-west, across the Great Kharesmian Desert to the Sea of Aral.  During the first 450 miles of its course, while it runs among the hills, it receives from both sides numerous and important tributaries; but from the meridian of Balkh those fail entirely, and for above 800 miles the Oxus pursues its solitary way, unaugmented by a single affluent, across the waste of Tartary, rolling through the desert a wealth of waters, which must diminish, but which does not seem very sensibly to diminish, by evaporation.  At Kilef, sixty miles north-west of Balkh, the width of the river is 350 yards; at Khodja Salih, thirty miles lower down, it is 823 yards with a depth of twenty feet; at Kerki, seventy miles below Khodja Salih, it is “twice the width of the Danube at Buda-Pesth,” or about 940 yards; at Betik, on the route between Bokhara and Merv, its width has diminished to 650 yards, but its depth has increased to twenty-nine feet.  Finally, at Gorlen Hezaresp near Khiva, the breadth of the Oxus is so great that both banks are hardly distinguishable at the same time; but the stream is here comparatively shallow, ceasing to be navigable at about this point.  The present course of the Oxus from its rise in Lake Sir-i-Kol to its termination in the Sea of Aral is estimated at 1400 miles.  Anciently its course must have been still longer.  The Oxus, in the time of the Achaemenian kings, fell into the Caspian by a channel which can even now be traced.  Its length was thus increased by at least 450 miles, and, exceeding that of the Jaxartes, fell but little short of the length of the Indus.

The Oxus, like the Nile and the Indus, has a periodical swell, which lasts from May to October.  It does not, however, overflow its hanks.  Under a scientific system of irrigation it is probable that a considerable belt of land on either side of its course might be brought under cultivation.  But at present the extreme limit to which culture is carried, except in the immediate vicinity of Khiva, seems to be four miles; while often, in the absence of human care, the desert creeps up to the very brink of the river.

The Jaxartes, or Sir-Deria, rises from two sources in the Thian-chan mountain chain, the more remote of which is in long. 79 deg. nearly.  The two streams both flow to the westward in almost parallel valleys, uniting about long. 71 deg..  After their junction the course of the stream is still to the westward for two degrees; but between Khokand and Tashkend the river sweeps round in a semicircle and proceeds to run first due north and then north-west, skirting the Kizil Koum desert to Otrar, where it resumes its