44 HARNESSING THE EARTHWORM 



cidentally is the mathematical midway point of this four-thousand- 

 mile, longest river in the world. Above Khartoum, between the 

 two converging rivers, lies a triangular stretch of level country 

 called the "Gezira." Roughly, the Gezira is 250 miles long, 100 

 miles wide at the base of the triangle and narrowing to the point 

 where the- rivers unite to form the Nile. This inexhaustibly fer- 

 tile, five-million-acre tract of ancient farm land has been slowly 

 built up through the ages by the annual deposit of silt from the 

 overflow of the Blue Nile, its waters so richly laden during the 

 flood season that it is almost a river of mud. The land of the 

 Gezira harbors an earthworm population, probably numbered in 

 the billions, which is responsible for the unexcelled fertility of 

 the soil. 



We must consider the region from which the Blue Nile 

 gathers its flood waters, in order to understand the composition 

 if its silt. At an altitude of 9000 feet, in the rugged highlands 

 of Abyssinia, the Blue Nile finds its source. For nine months of 

 the year this is a hard, dry country of volcanic mountains, abrupt, 

 fantastic peaks, high plateaus six to ten thousand feet in eleva- 

 tion vast, eroded slopes, deep gullies, narrow canyons. The river 

 dries up to occasional water holes. To the north of the river are 

 great timbered jungles which support an unequalled animal life, 

 including the elephant and other herbivora, as well as the great 

 carnivora and lesser animals of all kinds. 



In June of each year comes the rainy season, beginning with 

 torrential downpour, cloudbursts, terrific thunder and electric 

 storms. The trickling, almost dry river wakes from its nine 

 months' rest. Every gully, canyon, tiny tributary, and dry wash 

 becomes a roaring torrent, as the waters from thousands of square 

 miles of highlands rush down to swell the Blue Nile into a vast 

 wall of water fifteen hundred feet wide, as it starts on its course 

 to join the White Nile at Khartoum. In its first fifty miles the 

 river drops 4200 feet through a huge gorge, and thirty miles be- 

 low Lake Tana it encounters the great fall called "Tisitat" 

 "roaring fire." 



