From Idrisi's writings we learn that a century later, _i.e._ about the end of the eleventh century, the Seistan province extended far beyond its present limits. Bamian and Ghur (_i.e._ the central hills of Afghanistan) were _vis-à-vis_ to that province; Farah was included; and probably the whole line of the frontier hills from the Sulimanis, opposite Multan, to Sibi and Kalat. It was an enormous province, and a new light breaks on its traditional wealth in grain and agricultural produce when we understand its vast extent.
The regions of Ghur and Dawar bordered it to the north, and there is a word or two to be said about both hereafter. Ghur in the eleventh century included the valley of Herat and all the wedge of mountainous country south of it to Dawar, but how far Seistan extended into the heart of the mountain system which culminates to the south-west of Kabul it is difficult to say. It is difficult to understand the statement that Bamian, for instance, bordered Seistan, with Ghur in between, unless, indeed, in these early days of Ghur's history (for Ghur was only conquered by the Arabs in A.D. 1020, and was still far from intertwining its history with that of Ghazni when Idrisi wrote) the greatness of Bamian overshadowed the light of the lesser valleys of Ghur, and Bamian was the ruling province of Central Afghanistan. This, indeed, seems possible. The district of Dawar to the south of Ghur has always been something of a mystery to geographers. Described by Idrisi as "vast, rich, and fertile," and "the line of defence on the side of Ghur, Baghnein, and Khilkh," it would be impossible to place it without a knowledge of the towns mentioned, were it not that we are told that Derthel, one of the chief towns of Dawar, is on the Helmund, and that one crosses the river there "in order to reach Sarwan." This at once indicates the traditional ford at Girishk as the crossing-place, and Zamindawar as the Dawar of Idrisi. Khilkh then becomes intelligible also as a town of the Khilkhi (the people who then occupied Dawar, described as Turkish by Idrisi, and probably identified with the modern Ghilzai), and finds its modern representative in the Kalat-i-Ghilzai which crowns the well-known rock on the road from Kandahar to Kabul. "The country is inhabited by a people called Khilkh," says Idrisi. "The Khilkhs are of a Turkish race, who from a remote period have inhabited this country, and whose habitations are spread to the north of India on the flank of Ghur and in western Seistan." Thus the position of the Ghilzai in the ethnography of Central Afghanistan appears to have been established long before the days of Mongol irruption. Then as now they formed a very important tribal community.
