In modern times it is customary to divide the province of Fars into the ghermsir, or, “warm district,” and the serdsir, or “cold region”—­and the physical character of the country must have made such a division thoroughly appropriate at every period.  The “warm district” is a tract of sandy plain, often impregnated with salt, which extends between the mountains and the sea the whole length of the province, being a continuation of the flat region of Susiana, but falling very much short of that region in all the qualities which constitute physical excellence.  The soil is poor, consisting of alternate sand and clay—­it is ill-watered, the entire tract possessing scarcely a single stream worthy of the name of river—­and, lying only just without the northern Tropic, the district is by its very situation among the hottest of western Asia.  It forms, however, no very large portion of the ancient Persia, being in general a mere strip of land, from ten to fifty miles wide, and thus not constituting more than an eighth part of the territory in question.

The remaining seven eighths belong to the serdsir, or “cold region.”  The mountain-range which under various names skirts on the east the Mesopotamian lowland, separating off that depressed and generally fertile region from the bare high plateau of Iran, and running continuously in a direction parallel to the course of the Mesopotamian streams—­i.e. from the north-west to the south-east—­changes its course as it approaches the sea, sweeping gradually round between long. 50 deg. and 55 deg., and becoming parallel to the coast-line, while at the same time it broadens out, till it covers a space of nearly three degrees, or above two hundred miles.  Along the high tract thus created lay the bulk of the ancient Persia, consisting of alternate mountain, plain, and narrow valley, curiously intermixed, and as yet very incompletely mapped.  This region is of varied character.  In places richly, fertile, picturesque, and romantic almost beyond imagination, with lovely wooded dells, green mountain-sides, and broad plains suited for the production of almost any crops, it has yet on the whole a predominant character of sterility and barrenness, especially towards its more northern and eastern portions.  The supply of water is everywhere scanty.  Scarcely any of the streams are strong enough to reach the sea.  After short courses they are either absorbed by the sand or end in small salt lakes, from which the superfluous water is evaporated.  Much of the country is absolutely without streams, and would be uninhabitable were it not for the kanats, or karizes, subterranean channels of spring-water, described at length in a former volume.

The only rivers of the district which deserve any attention are the Tab (or Oroatis), whereof a description has been already given, the Kur or Bendamir (called anciently Araxes), with its tributary, the Pulwar (or Cyrus), and the Khoonazaberni or river of Khisht.