TRANSACTIONS OF SECTION G. 799 



The author submits that ■while such instances testify to the purifying powers of 

 aerated chalk, they afford proof that when superfluous waters are let down into the 

 water-bearing strata from above, they will pro tcmto spread and naturally raise 

 the line of saturation and the outflow of springs. 



The Raiydn Project for the Storage of Nile Flood. 

 By Cope Whitehotjse, M.A. 



This paper described a project for impounding a part of the surplus flood of the 

 Nile. A series of surveys show that the Wadi Raiyan is a depression 75 miles 

 to the S.S.W. of Cairo, communicating with the Nile Valley at +26 metres, or a 

 little below high Nile. Except at two narrow passes, it is bounded by precipitous 

 limestone hills rising to + 190 metres. The bottom, of sand and cla.j overlaying 

 rock, sinks to — 46 metres. A reservoir formed by putting this valley in communi- 

 cation with the Nile flood would have at + 30 metres a surface of 686 sq. kil. 

 (250 square miles), or 686 million square metres, and hold 20,559 million 

 cubic metres. At + 20 metres the surface is 550 million square metres, and con- 

 tents 14,876 million cubic metres. It would yield (without pumping) a net 

 40 million cubic metres per diem for 100 days, or about the average discharge of 

 low Nile from March to July. It would practically double the summer (Sefi) 

 irrigation of Egypt. 



The proposed works are : — 



(a) Cutting through the Myana Co^:- 3,500 metres long; summit level, 



+ 44 ; bed of canal, +21-8 ; average, 14 metres ; material (hard clay) 

 to be removed, about 75,000 cubic metres for each metre of bed width. 



(b) Dyke skirting desert : depth of water held up, 8 metres ; section, 140 



square miles ; length, 14,500 metres ; material (gravel, sand, and earth) 

 to be handled, about 2 million cubic metres. 



(c) Short low cut (1,500 metres) ; two short banks (500 metres) ; and a 



regulator. 



The works could be completed within one year, and the Wadi Lulu and Wadi 

 Safir, being detached from the Wadi Raiyan, could be used as small reservoirs 

 until the Raiyan Basin was available. It would require one season to fill the 

 small basins, and three to fill the Raiyan Reservoir. 



6. The Severn Watershed.^ By J. W. "Willis Bund. 



The Severn Watershed, with an area of 4,350 square miles, is the second 

 largest in England and Wales. The water supply within its area is no more than 

 sufficient for the population (1,500,000) and trades of the district. 



1. The Present Source of Sttpplt. 



The Severn, from its source to Beachley, in Gloucestershire, is 158 miles lono- 

 and its drainage area of 4,350 square miles, comprises parts of the followinc' 

 ten counties :— Montgomery, Denbigh, Radnor, Salop, Stafford, Northampton" 

 Warwick, Worcester, Hereford, and Gloucester. ' 



The Severn rises in one of the Montgomeryshire spurs of Plynlimon, about 

 2,000 feet above sea-level. At Llanidloes, 15 miles down, it is only 545 feet above 

 sea-level ; at Newtown, 12 miles, 358 feet ; at Montgomery, 8 miles, 306 feet ■ 

 at Welchpool, 8 miles, 270 feet ; at Shrewsbury, 32 miles, 179 feet. 'The fall of 

 the river in the 75 miles of its upper course is 1,821 feet ; at the end of the next 

 30 miles (Bewdley) the faU is 108 feet (179 to 71) ; at Stourport it is 53 feet • 

 at Worcester, 35 feet. In the next 40 miles, to Framilode, the fall is about 



' See Engineering, vol. xlvi. p. 267. 



2 Paper published in extenso in the Report of Severn Fishery Board for 1888. 



