Colonel Western, in a note on the Wadi Raiân, shows that for a certain number of years out of sixteen years (1872 to 1887, of which he had the statistics to work with) there is a surplus discharge in the Nile which might be abstracted without in any way interfering with the ordinary irrigation of the Delta. In his calculations he takes 565 million cubic metres in twenty-four hours as the discharge required by the Delta during September and the first half of October. He is, of course, referring to the conditions of the Delta at the present time. He gives the table which appears on the preceding page, to which I have added the corresponding gauge levels at Beni Suef and Magnûnah mouth for reference further on. The month of August has not been given, as the conclusion was come to that there was no water to spare in August under present conditions. The calculation, giving these figures, is made assuming that regulation on the Barrage below Cairo is not called in to assist; the discharges allowed to Lower Egypt, after abstracting the above quantities, being sufficient to give a water surface at the level required for irrigation without any heading-up. Now, the quantity required to fill the lake to R.L. 25·00, as found before, is 11,800 million cubic metres. This, let us suppose, would be made up thus:— September 30 days at 112 millions = 3,360 millions. October 31 „ 192 „ = 5,952 „ Parts of August and November 29 „ 86 „ = 2,494 „ ------ Total 11,806 „ These discharges could be abstracted without affecting Lower Egypt irrigation, as it exists now, for eleven years out of sixteen. This, however, is not a quite correct statement as applied to each of the eleven years, since the discharges given in the table are the _averages_ of those years in which a surplus discharge is available. Among these would be some very high years, in which it would be possible to fill the lake to a higher level than 25·00, and years when this level would not be reached. Besides the years, for which the averages of surplus discharges are taken, there would be five years out of sixteen when the supply would fall short in September, the month of highest level. There is no necessity in this stage to seek for a connection between the lake and the Nile for filling the lake, as the water would find its way in large volumes across all the low parts of the valley into the drainage depression along the edge of the Libyan Desert, now known as the Bahr Yûsuf.