164 BOARD OF AGRICULTURE. [Jan. 



of the Nile, the Atbara, which enters it in lat. 17° 45' N., 

 taking its waters from the Samen Mountains. 



The annual overflow of the Nile is one of the greatest 

 marvels in the physical geography of the globe ; with the 

 regularity of the re-appearance of the stars in their orbits 

 its movement may be expected, only retarded in hours or 

 minutes by adverse winds that slacken its current, rising to 

 within a few inches of the same height each year, and 

 remaining full about the same time ; this is recorded as 

 having taken place with almost unbroken regularity, for 

 nearly ten thousand years. There is evidence that there 

 have been failures and consequent famine ; from what cause 

 is unexplained. 



The rise is due to the prodigious rains that, in their 

 regular season, fall in the equatorial regions; the river 

 begins to swell about the 25th of June, and goes on with 

 gentle rise for three months, when it reaches its full volume. 

 It remains at flood twelve days, then subsides with the 

 same gradual and gentle action. The rise is about forty 

 feet at the tropic of Capricorn. At Thebes it is thirty-six 

 feet, flooding the Temples of Karnac on the other side of 

 the river, and rising to the knees of the vocal Memnon. In 

 ancient days these great works were protected with dykes. 

 At Cairo and the vicinity of the pyramids the rise is from 

 twenty-five to twenty-seven feet. Great effort has been 

 made from the earliest times to fill canals and artificial 

 basins with the water, and retain it for the subsequent 

 irrigation of lands distant from the river ; these works exist 

 in all parts of the country where there is any considerable 

 breadth to the valley, and it is a large part of the business 

 of government to maintain them. 



The first sight of the full Nile is at Cairo. Here it is 

 a powerful stream, about five-eighths of a mile wide, flowing 

 with strong current between high banks, and crossed by a 

 fine suspension bridge. The great city of Cairo is chiefly 

 on the right bank, but it extends to the other side, and the 

 pyramids, though five or six miles away, seem to rise above 

 the sycamore and acacia groves not half a mile from the 

 bank. 



The Nile is peculiar in various aspects. It differs from all 



