In my former calculations of the volumes of water required to fill the Fayûm depression to higher levels, I have taken the area of the depression at 2000 million square metres. But our mean water level is now R.L. 21·00, and the area of the lake will be reduced. The present taxed area in the Fayûm is nearly 234,000 feddans.[8] ------- The actual cultivated area is more probably about 280,000 „ The area of the Birket-el-Qurûn is about 70,000 „ ------- Total 350,000 „ 350,000 feddans = 1,470,000,000 square metres. Add the uncultivated area below R.L. 21·00 = 300,000,000 ------------- Total 1,770,000,000 Deduct areas reclaimed from Lake Mœris:— 1st reclamation 40,000,000 2nd „ 24,000,000 3rd „ 40,000,000 ---------- 104,000,000 ------------- Remaining for area of Lake Mœris 1,666,000,000 or, say, 1600 million square metres. Now let us suppose that the exit channel joins the Nile at the point where Kosheshah Escape has been built, a little above Wâstah (Plate XXI.) The lowest summer levels at Wâstah were in 1887, 18·82; 1888, 18·12; 1889, 18·26. Let us then call the mean L.W.L. of Wâstah 18·50. As the exit channel would be of considerable dimensions, we may suppose a water-surface slope, at the _final_ date of outflow, of ¹⁄₅₀₀₀₀. The distance from Wâstah to Lahûn is 25 kilometres, and from Lahûn to Hawârah 10 kilometres; total 35 kilometres. The fall in this distance would then be 0·70, which would make the level at Hawârah, or the level of the lake (18·50 + 0·70 =) 19·20. But the outflow, even at the date of the lowest level of the Nile, before the rise commenced, may be assumed to have raised the Nile 30 centimetres, which would make the lowest level of the lake R.L. 19·50. The water surface of Lake Mœris would therefore oscillate between the level of 22·50, beyond which the regulator would be used to prevent its rising, and R.L. 19·50, below which it could not fall on account of the level which the Nile maintains at its point of union with it.