SUMATEAN EIVEES. 91 



alluvial lands are also of great extent. The enormous volume of rain water 

 precipitated on both, slopes of Sumatra explains the exceptional importance of this 

 fluvial action. On an average Padang receives a mean annual rainfall of about 

 150 inches ; Palenibang, on the opposite side, is still more copiously watered, and 

 all the heaviest downpours fall on the advanced slopes of the mountains, so 

 that little is lost by evaporation or infiltration before the streams reach the 

 plains. 



The Asahan, which receives the overflow of Lake Toba, belongs to the eastern 

 slope. Farther south follows the Rokau, which enters the strait of Malacca 

 through two muddy estuaries. It has a course of about 120 miles, nearly half of 

 which winds through low-hing lands created and levelled by itself. Both the 

 Siak and the Kampar disembogue in the labyrinth of marine channels washing the 

 muddy shores of the archipelago lying to the west of Singapore. Although 

 navigable for over 60 miles from their mouth, these two streams wind through 

 almost uninhabited plains, whose climate is fatal to strangers. 



Beyond the Kampar follows the Indragiri, which like it rises near the west 

 coast on the Padang plateau. After traversing Lake Singkarah it flows under 

 the name of the Umbilien through early Tertiary formations rich in carboniferous 

 beds. Farther on it escapes from a region of plateaux through a series of falls and 

 rapids, and after running for some distance parallel with the Kampar, mingles its 

 waters with those of Amphitrite Bay. Near its mouth the southern and much 

 smaller basin of the Reteh also contains some carboniferous rocks. Vessels ascend 

 the Indragiri for many miles inland, but not as far as the neighbourhood of the 

 coalfields. 



The Jambi, whose farthest headstreams rise north and south of Indrapura, 

 culminating point of the island, has the largest area of drainage and rolls down 

 the greatest volume of water. At the town of Jambi, 60 miles above its mouth, it 

 is nearly 500 yards broad and over 16 feet deep, at low water, and during the 

 floods its volume is more than doubled. Steamers drawing three feet ascend the 

 Jambi and its main branch, the Hari, for 360 miles from the sea, while small 

 canoes penetrate 100 miles higher up. 



The Musi, or Palembang river, which also rises on the uplands near the west 

 coast, collects the waters of the eastern slope for a space of about 200 miles before 

 entering the low-lying plains. Here it divides below the city of Palembang into 

 several branches, which ramify into endless channels and backwaters amid the 

 surrounding swamps. The Susang, or main branch, which falls into the Bangka 

 Strait near its north entrance, preserves sufficient water to give access to large vessels 

 during the floods, and to smaller craft throughout the rest of the year. But the 

 other braiiches all merge in other streams to the right and left, developing shallow 

 lagoons, expanding into broad morasses, or mingling with marine waters through the 

 dense mangrove forests. These half submerged, uninhabited and, for the most 

 part, almost uninhabitable tracts cover a total area of some 5,000 square-miles. 



According to the local traditions, which however may have been insjjired by 

 the undeniably rapid encroachments of the land on the sea, the whole of this 



