Ílí is bounded north by the Altai range, separating it from the Kirghís; northeast by the Irtysh River and Outer Mongolia; east and southeast by Urumtsi and Barkul in Kansuh; south by the desert and the Kwănlun range; and west by the Belur-tag, dividing it from Badakshan and Russian territory.[117] In length, the Northern Circuit extends about nine hundred miles, and the width, on an average, is three hundred miles. The Southern Circuit reaches nearly twelve hundred and fifty miles from west to east, and varies from three hundred to five hundred in breadth, as it extends to the Kwănlun range on the south. There is probably most arable land in the Northern Circuit. ~TOPOGRAPHY OF ÍLÍ.~ Ílí, taken north of the Tarim basin, may be regarded as an inland isthmus, extending southwest from the south of Siberia, off between the Gobi and Caspian deserts, till it reaches the Hindu Kush, leading down to the valley of the Indus. The former of these deserts incloses it on the east and south, the other on the west and northwest, separated from each other by the Belur and Muz-tag ranges, which join with the Tien shan, that divide the isthmus itself into two parts. These deserts united are equal in extent to that of Sahara, but are not as arid and tenantless. This region has some peculiar features, among which its great elevation, its isolation in respect to its water-courses, and the character of its vegetation, are the most remarkable. Songaria is especially noticeable for the many closed river-basins which occur between the Altai and Tien shan, among the various minor ranges of hills, each of which is entirely isolated, and containing a lake, the receptacle of its drainage. The largest of these singular basins is that of the River Ílí, which runs about three hundred miles westward, from its rise in the Tien shan (lat. 85°) till it falls into Lake Balkash, which also receives some other streams; the superficies of the whole basin is about forty thousand square miles. The other lakes lie north-eastward of Balkash; the largest of them are the Dzaisang, which receives the Irtysh, the Kisilbash, into which the Urungu flows, and four or five smaller ones between them, lying north of the city of Ílí. Lake Temurtu, or Issik-kul, lies now just beyond the southwestern part of this Circuit, and was until recently contained therein. This sheet of water is deep and never freezes; it is brackish, but full of fish; the dimensions are about one hundred miles long, and thirty-five wide; its superabundant waters flow off through the Chu ho into the Kirghís steppe.