In the time of the Fifth Monarchy, the tract which has been here described was divided among three nations.  The region immediately to the east of the Caspian, bounded on the north by the old course of the Oxus and extending eastward to the neighborhood of Merv, though probably not including that city, was Chorasmia, the country of the Chorasmians.  Across the Oxus to the north-east was Sogdiana (or Sugd), reaching thence to the Jaxartes, which was the Persian boundary in this direction.  South of Sogdiana, divided from it by the Middle and Upper Oxus, was Bactria, the country of the Bakhtars or Bactrians.  The territory of this people reached southward to the foot of the Paropamisus, adjoining Chorasmia and Aria on the west, and on the south Sattagydia and Gandaria.

East of the table-land lies the valley of the Indus and its tributaries, at first a broad tract, 350 miles from west to east, but narrowing as it descends, and in places not exceeding sixty or seventy miles, across.  The length of the valley is not less than 800 miles.  Its area is probably about a hundred thousand square miles.  We may best regard it as composed of two very distinct tracts—­one the broad triangular plain towards the north, to which, from the fact of its being watered by five main streams, he natives have given the name of Punj-ab, the other the long and comparatively narrow valley of the single Indus river, which, deriving its appellation from that noble stream, is known in modern geography as Sinde.  The Punjab, which contains an area of above fifty thousand square miles, is mountainous towards the north, where it adjoins on Kashmeer and Thibet, but soon sinks down into a vast plain, with a soil which is chiefly either sand or clay, immensely productive under irrigation, but tending to become jungle or desert if left without human care.  Sinde, or the Indus valley below the Punjab, is a region of even greater fertility.  It is watered, not only by the main stream of the Indus, but by a number of branch channels which the river begins to throw off from about the 28th parallel.  It includes, on the right bank of the stream, the important tract called Cutchi Gandava, a triangular plain at the foot of the Suliman and Hala ranges, containing about 7000 square miles of land which is all capable of being made into a garden.  The soil is here for the most part rich, black, and loamy; water is abundant; and the climate suitable for the growth of all kinds of grain.  Below Cutchi Gandava the valley of the Indus is narrow for about a hundred miles, but about Tatta it expands and a vast delta is formed.  This is a third triangle, containing above a thousand square miles of the richest alluvium, which is liable however to floods and to vast changes in the river beds, whereby often whole fields are swept away.  Much of this tract is moreover low and swampy; the climate is trying; and rice is almost the only product that can be advantageously cultivated.