584 



SCIENCE. 



[N. S. Vol. XXII. No. 567. 



East and west of this lies a country broken 

 into hills and valleys, wild crags, level 

 stretches, but everywhere absolutely sterile, 

 dry sand and rock, at such a level that the 

 Nile flood has never reached it to cover its 

 nakedness with fertile deposit. A few 

 miles north of Cairo the river bifurcates, 

 and its two branches flow each for about 

 130 miles to the sea. As you are probably 

 aware, with rivers in a deltaic state the 

 tendency is for the slope of the country to 

 be away from the river, and not towards 

 it. In the Nile Valley the river banks are 

 higher than the more distant lands. From 

 an early period embankments were formed 

 along each side of the river, high enough 

 not to be topped by the highest flood. At 

 right angles to these river embankments 

 others were constructed, dividing the whole 

 valley into a series of oblongs, surrounded 

 on three sides by embankments, on the 

 fourth by the desert heights. These ob- 

 long areas vary from about 50,000 to 3,000 

 acres. I have said the slope of the valley 

 is away from the river. It is easy, then, 

 when the Nile is low, to cut short deep 

 canals in the river banks, which fill as the 

 river rises and carry the precious mud- 

 charged water into these great flats. There 

 the water remains for a month or more, 

 some three or four feet deep, depositing its 

 mud, and then at the end of the flood it 

 may either be run off direct into the reced- 

 ing river, or cuts may be made in the cross 

 embankments and the water passed off one 

 flat after another, and finally rejoin the 

 river. This takes place in November, when 

 the river is rapidly falling. Whenever the 

 flats are firm enough to allow a man to walk 

 over them with a pair of bullocks, the mud 

 is roughly turned over with a wooden 

 plough, or even the branch of a tree, and 

 wheat or barley is immediately sown. So 

 soaked is the soil after the flood that the 

 seed germinates, sprouts and ripens in 

 April without a drop of rain or any more 



irrigation, except what, perhaps, the owner 

 may give from a shallow well dug in the 

 field. In this manner was Egypt irrigated 

 up to about a century ago. The high river 

 banks which the flood could not cover were 

 irrigated directly from the river, the water 

 being raised as I have already described. 



THE BARRAGE. 



With the last century, however, appeared 

 a very striking figure in Egyptian history, 

 Muhammed Ali Pasha, who came from 

 Turkey a plain captain of infantry, and 

 before many years had made himself 

 master of the country, yielding only a very 

 nominal respect to his suzerain lord, the 

 Sultan, at Constantinople. 



Muhammed Ali soon recognized that with 

 this flood system of irrigation only one 

 cereal crop was raised in the year, while 

 with such a climate and such a soil, with 

 a teeming population and with the markets 

 of Europe so near, something far more 

 valuable might be raised. Cotton and 

 sugar-cane would fetch far higher prices; 

 but they could only be grown at a season 

 when the Nile is low, and they must be 

 watered at all seasons. The water-surface 

 at low Nile is about twenty-flve feet below 

 the flood-surface, or more than twenty feet 

 below the level of the country A canal, 

 then, running twelve feet deep in the flood 

 would have its bed thirteen feet above the 

 low-water surface. Muhammed Ali or- 

 dered the canals in lower Egypt to be deep- 

 ened; but this was an enormous labor, and 

 as they were badly laid out and graded they 

 became full of mud during the flood and 

 required to be dug out afresh. Muhammed 

 Ali was then advised to raise the water- 

 surface by erecting a dam (or, as the 

 French called it, a barrage) across the 

 apex of the delta, twelve miles north of 

 Cairo, and the result was a very costly and 

 imposing work, which it took long years 

 and untold wealth to construct, and which 



