From the summit of Nanga Parbat to the waters of the Indus below is in depth nearly 24,000 feet. On the opposite side, the naked hill-sides rising in precipice after precipice are entirely barren of all vegetation. Waterworn into innumerable gullies and rock towers, they present a melancholy and arid appearance; and, although their summits are 12,000 feet above the Indus, they do not form a north side to this gorge in any way comparable with that on the south. The floor of the valley is filled with the debris of countless Himalayan deluges, yet the Indus looks like a small and dirty stream. To appreciate in any way the gigantic scale of the whole is quite impossible. What is the depth of that stealthily flowing flood and the measure of its waters, who can say? For it is more than six hundred miles from its source, and its tributaries sometimes are almost as big as itself. From the borders of Swat and Chitral, from the Darkot pass, from the Kilik beyond Hunza, and from the Hispar pass, the waters collect to form the Gilgit river, one only of the many tributaries of the Indus. This tract of the Mustagh range is nearly two hundred miles long by eighty broad. The Shigar river drains the waters from the Mustagh range and K^{2}, perhaps the greatest accumulation of ice and snow that exists outside the arctic regions. The Nubra and Shayok rivers collect their waters from a yet larger area. But still east of all these tributaries, the Indus itself rises three hundred miles away in those unknown lands of Tibet behind the Himalaya and near the source of that mysterious river of eastern India, the Bramaputra. Yet all these collected waters are penned into this apparently slow flowing and narrow river, as with silent but stealthy haste it twists and turns through the gigantic chasm at the base of Nanga Parbat. Once, not many years ago, in December 1840, into the upper end of this gorge the side of the Hatu Pir fell, forming a dam probably over 1000 feet high.[K] A lake was formed behind it for miles. The water rose to the level of Bunji fort, 300 feet above the river below, and up the Gilgit valley this lake, newly formed, reached nearly to Gilgit itself. For six months the waters were held back till, topping the vast accumulation, they burst the dam, 'and rushed in dark tumult thundering.' The lake is said to have emptied in one day. A small remnant of the barrier can still be seen near Lechre on the Chilas road.