ABSTRACT OP PROCEEDINGS — APPENDIX. XXIX, 



APPENDIX. 



Popular Science Lecture, "Irrigation in India and 



in Egypt." 



By Professor W. H. Warren, ll.d. 



(Delivered in the Society's Hall, October 16th, 1913.) 



Introductory. 



Irrigation is of very ancient origin, and it appears to 

 have been practised in Mesopotamia and Egypt several 

 thousand years before the Christian Era. The earliest 

 form was probably a natural inundation system brought 

 about by rivers overflowing their banks and flooding the 

 lands bordering on their lower reaches. This appears to 

 have been the origin of the Basin System which has been 

 so largely practised ia Egypt and which, in the time of 

 Joseph, made it the principal producer of corn for the 

 adjoining countries. 



Rivers such as the Nile in Egypt and those in Northern 

 India having seasons of periodic flood, generally have their 

 source in mountain ranges where the rainfall is heavy and 

 the formation rocky. The stream is at first torrential in 

 character, and flows rapidly down the steep slopes carrying 

 with it material eroded from its bed and the sides of the 

 valley in which it flows. The slope becomes less steep 

 and the velocity less rapid as it approaches the foot of the 

 hills where the heavier material carried in suspension is 

 deposited. The river flows in a more or less deep channel 

 through the flatter country in its course towards the sea, 

 gradually diminishing in velocity and increasing in width 

 until it reaches at length the region where it overflows its 

 banks in times of flood. The material hitherto carried in 

 suspension is deposited, gradually raising the level of the 

 bed and banks and spreading its silt on the adjacent lands. 



