442 Report S.A.A. Advancement of Science. 



middle of June ; the river rises slowly through July and fairly quickly 

 in August, and reaches the average maximum discharge of about 

 268,000 cubic feet per second about the beginning of October. 

 Thiough October the Nile at Cairo is practically stationary, and 

 falls rapidly in November, and continues to decrease until the 

 arrival of the next year's floods. 



In order that the Nile may exercise its powers of sustaining 

 life and assisting plant growth, there are certain physical conditions 

 that must exist ; and these conditions are that the relative levels of 

 land and water should be such that the water may flow over the 

 surface of the land. Such conditions exist naturally at certain 

 places in time of flood. When they do not naturally exist there is 

 no active life, unless the necessary conditions are produced artifically 

 by engineering works. Such works, of a primitive nature, resulting 

 in the practice of irrigation, have existed from pre-historic times. 

 Prior to 1805 the whole of Egypt was irrigated by what is known 

 as the basin system ; that is, by inundation, and depended on the height 

 of the flood for its water supply. The country was traversed by 

 dykes running more or less at right angles to the river, starting from 

 its bank, and reaching the desert. A dyke running parallel with 

 the river along its bank enclosed the basin on its river side, while 

 the desert usually formed the fourth side. Almost all the basins 

 had special canals leading directly into them the floods charged 

 with alluvium, and they also possessed escapes which allowed the 

 water, after it had deposited its alluvium, and stood some forty days 

 on the land, to flow back to the river. On the mud thus produced 

 the crops were sown, and received no further watering. 



Certain basins that are at too high an elevation to be flooded 

 naturally directly from the river, receive their water from basins 

 upstream of them. By passing water from basin to basin it is 

 possible to lead water parallel to the river at a flatter slope than 

 that of the Nile, and thus to reach land that could not otherwise be 

 flooded. 



Under the basin system of irrigation, winter crops only, such as 

 barley, wheat, beans and clover are grown on the lands from which 

 the Nile flood had retired after watering them. During the reign 

 of Mehemet AH, however, who became Viceroy of Egypt in 1805, 

 the development of cotton cultivation in Lower Egypt necessitated a 

 radical change in the whole irrigation system. This crop could not 

 be grown under the basin system, as it requires to be protected from 

 inundation, and must be planted and irrigated before the Nile begins 

 to rise. It became necessary to embank the branches of the river, 

 which had previously found its wav to the sea through the basins 

 and minor channels, and to dig deep canals to bring the low-level 

 water of the summer Nile to the crops, which were then irrigated by 

 means of pumps. To keep the Nile bank in such repair that they 

 could resist high floods, and to dig and clear the canals so that they 

 should be deep enough to flow at Low Nile, was a very heavy tax on 

 the country, and it was necessary to have recourse to some more 

 scientific method for obtaining and distributing water. 



