— 43 — 
4000 cubic metres per second in September 1876 and mentioned in his 
book u Le Nil , le Soudan , V Egypte” page 17. 
In 1903 the minimum discharge of the White Nile at its head was 
380 cubic metres per second in April and the maximum discharge 
was 1470 cubic metres per second in December. Table 24 gives the 
behaviour of the river. The minimum discharge of the White Nile 
at Khartoum may be taken as 300 cubic metres per second. The 
preceding paragraph will explain how difficult it will be to know its 
maximum discharge until a gauge and discharge table are established 
for the Blue Nile 100 kilometres above Khartoum well above back 
water, and a gauge and discharge table in the Main Nile north of 
Omdurman. The difference between these two discharges will be the 
true discharge of the White Nile which, with its slope of yooWo m 
flood, is not a river but a flood reservoir. The discharges taken at 
Duem on the White Nile and at Khartoum on the Blue Nile in 
1902 and 1903 are interesting, but of little value for anything except the 
very date on which they were taken. They were all in backwaters. 
19. The Blue Nile.— Compared to any river we have yet described, 
the Blue Nile is a true mountain stream. Draining the southern and 
more rainy half of Abyssinia, it is the principal source of the Nile in 
flood. Whatever waters it receives, it carries to the Nile and it is the 
true parent of the land of Egypt, for the deposit from its muddy waters 
is that Nile mud which has made Egypt. The Atbara carries waters 
which are probably more muddy than those of the Blue Nile, but 
compared to the Blue Nile the Atbara is a small river, and its quota 
is insignificant by the side of that of the larger stream. The principal 
tributary of the Blue Nile, the Abai, rises at a height of about 2,700 
metres above sea level and after a course of 110 kilometres falls into Lake 
Tsana. Lake Tsana lies at a level of about 1,760 metres above sea level, 
and has an area of about 3,000 square kilometres and catchment basin 
of about 14,000 square kilometres irrespective of the lake area. On the 
31st of January 1903, after a very poor rainfall, Mr. C. Dupuis found the 
discharge 42 cubic metres per second. Calculating from his cross section, 
it seems that the maximum discharge may be 200 cubic metres per 
second. As at Lake Victoria, possibly not more than y^th the rainfall 
finds its way into the lake ; and, once there, the greater part is evapor- 
ated. Little seems to leave the lake, which would consequently make a 
very poor reservoir. The land rises from the lake in gently undulat- 
ing downs as a rule. Wherever observed by Mr. Dupuis, the lake was 
