608 THE FRESH-WATER LOCHS OF SCOTLAND 
fractures of the earth's crust, which caused a strip of country from 
about Edfu, in lat. 25° N., to Cairo, in lat. 30° N., to be depressed, 
leaving the plateau on either side standing high above it, just as the 
Red Sea and the Gulfs of Suez and Akaba are supposed to have 
been formed probably about the same epoch. Into this depressed 
area the drainage of the southern part of the basin finally flowed, 
and there was laid down during a long period the bed of alluvial 
deposit from SS to 60 feet (10 to 18 metres) in thickness, through 
which the river runs to-day. The valley of Egypt is therefore the 
normal plain tract of the ancient river, and it is the portion inter- 
vening between that and the White Nile which gives indications of 
having renewed its youth. 
The Nile rises in Victoria Nyanza, which occupies a shallow 
depression 26,i^48 square miles in extent on the plateau of the 
equatorial lakes, a region lying at an average elevation of from 4000 
to 5000 feet above sea-level. That the earth-movements on the 
surface of the plateau are comparatively recent is shown by the 
moderate amount of weathering which has taken place, and by the 
incomplete development of the drainage system. As yet the rivers 
have not had time to deposit and erode sufficiently to give a regular 
grade to their beds, so that marshes and water-logged depressions 
still alternate with reaches in which the fall is considerable and the 
flow therefore rapid. The Victoria Nile, issuing from Victoria Nyanza, 
flows over the Ripon Falls, pours down 60 miles of rapids, to the 
still waters of Lake Choga. At Foweira 50 miles of rapids begin, 
ending at the Murchison Falls, 120 feet high ; immediately beyond 
the material eroded from the rocky bed and brought in by tributary 
streams is forming extensive mud-flats where the Victoria Nile enters 
Lake Albert. 
Victoria Nyanza. — The surface of Victoria Nyanza is 3720 feet 
above sea-level ; ^ on its north side the land-surface descends gradually 
to Lakes Choga and Kwania, which lie at an altitude of about 
3500 feet, and from there to Albert Nyanza, 2138 feet above sea-level. 
Victoria Nyanza, which has roughly the form of a parallelogram, being 
about 200 miles in length by 130 in average breadth, with an area of 
26,000 square miles, is outlined by earth-movements, and there is 
definite evidence ^ furnished by the comparative readings of the lake- 
1 The heights given for the lakes dealt with are the trigonometrical heights 
taken from a paper by Capt. T. H. Behrens, R.E., on " The most Reliable Values 
of the Heights of the Central African Lakes and Mountains," Geogr. Journ., 
vol. xxix. p. 307, 1907 ; those for Victoria and Albert Nyanzas are from a 
subsequent letter from Capt. Behrens published in the Geogr. Journ., vol. xxx. 
p. 219, 1907. 
^ See H. G. Lyons, Physiography of the River Nile and its Basi?i, pp. 18, 43^ 
Cairo, 1906. Lyons' conclusion is questioned by Craig (Cairo Sci. Journ., Aipril 1909). 
