The province of Herat extends from near the sources of the Hari Rud on the east to the Persian frontier on the west, and from the Russian southern boundary to the northern limits of Seistan. The area is 300 miles from east to west and 200 miles from north to south. North, south and west there are tracts of unproductive country, presenting facilities for development only over restricted surfaces. In the east the upper reaches of the Hari Rud valley stretch away to the mountain regions of the Koh-i-Baba. It has been estimated that the valley of the Hari Rud is capable of furnishing supplies for an army of occupation which should not exceed 150,000 men. It is this fact, coupled with the value of its position as the converging point of roads from the Caspian, Merv, Meshed, Bokhara, and from India through Kandahar, which has invested Herat with the title of The Key of India. The Hari Rud oasis presents a wonderful appearance of fertility; near the city groves of pistachia and mulberry trees, blackberry bushes, wild roses and innumerable settlements abound. The Hari Rud, flowing in a single channel 100 to 140 feet in width which diminishes as the summer wanes, has been the means of converting into a smiling paradise the surrounding wilderness. Flood-water in this river lasts from the close of January until the end of March, when fords are dangerous to cross. The subsidence of flood-water in April makes it more readily passable, the average depth of the fords then measuring 4 feet. Later, when the warmer weather appears, the permanent channel breaks up into long lakes, fed by springs and underground continuations of supplementary streams. The northern extremity of the river, which waters the Tejend oasis and the Sarakhs region, preserves in the main the characteristics of the upper stream. The undulating country between the Hari Rud and the Murghab, extending from the northern slopes of the Paropamisus to the edge of the Kara Kum, is called Badghis. At one time this district included the oasis of Yulatan and, even now, it embraces Pendjeh. Across it, along the banks of the Murghab and through the valley of the Kushk, runs the direct road from Merv to Herat. From the levels of valleys within Russian jurisdiction, which are about 2000 feet above sea-level, the road rises throughout a distance of 35 miles until it pierces the Paropamisus range by the Ardewan pass, 4700 feet above sea-level. From these mountains, it descends across the broken slopes of the Koh-i-Mulla Khwaja until it meets at last the alluvial flats of the Hari Rud plain, wherein the city of Herat stands, 2600 feet above sea-level.