It rises in the southern slopes of Siah-Koh, which forms the southern wall of the valley of Herat, and after a south-westerly course of about 200 m.
RESHT, the capital of the province of Gilan in Persia, in 37° 17' N., and 49° 36' E., on the left bank of the Siah-rud (Black river), which is a branch of the Sefid-rud (White river), and flows into the Murdab, lagoon of Enzeli.
Before it takes its great northern bend at Kuhsan, and passes northwards through the broken ridges of the Siah Bubuk (the western extremity of the range which we now call Paropamisus) towards Sarakhs.
From Nushki it crosses the Helmund desert, touching the crest of a well-defined mountain watershed for a great part of the way, and, leaving Chagai to Baluchistan, it strikes nearly west to the Persian frontier, and joins it on the Koh-i-Malik Siah mountain, south of Seistan.
Goldsmid's Commission in 1872 from the Malik-Siah-Koh to the Helmund Lagoons, and rectified by the Commission under Sir Henry MacMahon in 1903-1905.
The boundary between Baluchistan and Afghanistan, starting from Nushki, cuts across the Lora hamun, leaving the frontier post of Chagai to Baluchistan, and from this point to the Malik Siah Koh it is based partly on the central moun tainous water-divide already referred to, and partly runs in straight lines through the desert south of the salt swamps of the Gaud-i-Zirreh.