THE EARTHWORM IN SCIENTIFIC LITERATURE 45 



Below the falls the river is crowded into an almost inacces- 

 sible gorge, at places 5000 feet deep, between whose precipitous 

 walls it pursues its course for 500 miles. This gorge is an almost 

 uninvaded jungle paradise for animals and birds. The tempera- 

 ture never falls below 100 degrees. The accumulated droppings 

 of months from millions of animals and birds, including ele- 

 phants, hippopotami, crocodiles, lions, leopards, and an aggrega- 

 tion of beasts great and small, find their way into the river to add 

 to its rich silt. The downpour of rain continues for nearly one 

 hundred days, with very little let-up. The rushing, eroding 

 waters from the highlands gather vast quantities of volcanic ash, 

 ferruginous minerals, feldspar, hornblende crystals, clay, etc., 

 down the steep hillsides into the Blue Nile, until the river carries 

 17 per cent of silt, of which 9 per cent is organic matter and 8 

 per cent mineral matter. 



A peculiar element which adds appreciably to the organic 

 richness of the silt of the Blue Nile is billions of white ants, with 

 the numberless tons of fine earth they have piled up in their 

 ceaseless workings during the nine month's dry season. 



After flowing 500 miles through the confines of this great 

 canyon, a boiling, mixing cauldron of racing, silt-laden waters, 

 the river bursts from the gorge into the lowland of the Gezira 

 and spreads over the plain as overflow. In the Gezira more than 

 9000 miles of irrigation ditches help to distribute the flood 

 waters uniformly over the earth. 



It is thus that the vast annual feast of organic and inorganic 

 material, perfectly mixed and composted, is spread for the worms 

 of the Gezira. Beneath the dry surface of the earth the innu- 

 merable earthworm population has awaited the coming of the 

 rains. The earth has been riddled with billions of tunnels to a 

 depth of several feet, making it one vast honey-combed sub- 

 surface, ready to receive and store the waters when they come. 

 As the flood-water spreads, the thirsty earth absorbs it quickly 

 like a sponge, leaving its deposit of silt. The earthworms begin 

 their work and almost over night the silt is carried through the 



