Higher up, waterfalls and rapids hinder navigation, but the valleys, including those of the tributaries, nevertheless provide access to the otherwise hard-to-reach regions of Kafiristan, Badakhshan, Chitral, Wakhan, and the Pamirs, all located north of the Kabul. From the south comes the important tributary Logar, in whose valley lies the city of Kabul. – Population. Although Afghanistan has fairly sharp natural borders in the North and South, in the East and West, the population has not amalgamated, either into a national or an ethnic unit. The inhabitants belong to different ethnic groups, each with very conflicting interests. Religion alone forms a bond which unites most into a whole which could resist the interference of other Christian powers. Except for the inhabitants of Kafiristan, all are Mohammedans. Those who are not co-religionists are given the name Kafirs, hence the word Kafiristan. A small minority, the Kizilbashis and Hazaras, belong to the Shia, the great majority to the Sunnites. The country probably has a total of 4½ to 5 million inhabitants, of which the 3½ million Afghans make up the main population. They regard themselves as descendants of Jews who were taken from Palestine by Nebuchadnezzar, but ethnological research has shown this to be a folk tradition. It is probable that Turkish elements have exerted a great influence on these Iranians, and that Semitic blood flows through their veins at the same time. They are divided into many tribes. In the south-west, from Kandahar to Kelat, dwell the Durranis or Abdalis, who number with the Ghilzais one and a half million souls, and therefore form the most powerful tribe. These Ghilzais, who are among the bravest of the Afghans, have taken possession of the whole north-east, including the triangle between Herat, Kabul, and Farrah. Moreover, the tribes of no more than 100,000, some of as few as 5,000 members are numerous. Among these, the 250,000 strong Wasiri are certainly the foremost. See itypeauto for Afghanistan Arts and Literature.