CKARACTERISTICS AND DISTRIBUTION OF LAKES 605 
depth in places of 50 feet. It is also fed by streams from the Pnom 
Dangrik range to the north and from the west. It consists of two 
basins divided by narrows ; the north-western being called Caman 
Dai, and the south-eastern Caman Tien. Fishing is carried on to a 
great extent in its waters during the season of low water. 
Toba Lake. — In the mountainous regions of Sumatra are numer- Sumatra, 
ous lakes, much the largest of which is Lake Toba, lying at an 
altitude of between 2500 and 3000 feet above sea-level. It trends 
in a north-west and south-east direction, and is about 50 miles in 
length by about 16 miles in average breadth, with an area of about 
800 square miles. The mountains surrounding the lake are high, with 
very steep slopes, and the small streams running from them in short, 
rapid courses are the only visible affluents. The outflow is by one of 
the head-streams of the Assahan River, which flows to the Malacca 
Strait. The lake is divided into two basins by a large island, the 
water between it and the western shore being so shallow that it is 
possible to ford it on foot at times of low water.^ 
The lakes of Eastern Africa belong to two types, the one circular Africa. 
in shape, with shelving shores, like the Victoria Nyanza, the other 
long, narrow, and fiord-like, lying between high, precipitous cliffs, like 
Lake Tanganyika. The latter type occurs on two lines of depression 
passing one on either side of the Victoria Nyanza and meeting at 
Basso Narok (Lake Rudolf), thence continuing northward to the Red 
Sea as a long strip of low land, in places below the level of the sea, 
with many lakes and old lake-basins occurring at intervals. At the 
northern end of the Red Sea the Gulf of Akaba leads to a valley 
with the same structure, and thence to the plains of Northern Syria. 
The eastern and western portions of this long depression are to some 
extent linked together by a subsidiary valley lying farther to the 
east, which contains Lake Rukwa and enlarges towards the south to 
form the bed of Nyasa. Suess considers that once the plateaus which 
now form scarps on either side of the depression were continuous ; 
volcanic action left dominant lines of weakness running almost 
parallel from north to south, and subsequently faulting along these 
lines allowed the block of material between to subside, leaving a 
great open rift valley with almost vertical sides. 
Though Suess has many followers in his conception of the forma- 
tion of what has been termed the " Graben or Great Rift Valley, 
Moore, who visited the region in 1896 and 1899, does not share his 
views, but regards the depression as a consequence of the folding due 
1 See J. von Brenner, " Besuch bei den Kannibalen Sumatras," Wiirzburg, 
1894 (reviewed by Baron A. von Hiigel, Geogr. Journ., vol. vii., p. 75, 1896). 
