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.
On the map of Linant Pasha’s, published in 1854, before the railway and Ibrahimîyah Canal were made, the channels in the Nile Valley shown in connection with the Lahûn entrance are the Bahr Yûsuf, coming from the south, and the Magnûnah Canal going north. The latter, after going north for 13 kilometres, is joined by three channels, the first taking off from the Nile at Beni Suef, and the second and third a little south of Ashment. The third is the old Magnûnah. These channels unite in the neighbourhood of Abûsir-el-Malaq, the second passing by the village of Bûsh, the immense heap, on which the modern village stands, witnessing to the existence of an ancient town on that spot. Abûsir-el-Malaq also was evidently in the far past a place of importance. North of Abûsir-el-Malaq the channel of the Magnûnah is continued as a single channel along the west desert for 4 or 5 kilometres when it bifurcates, one branch continuing under the western desert, and the second going east to join the Nile at the point where Kosheshah Escape now stands. Some of these channels are shown on [Plate XXI.]
Having evidence of no other channels, let us suppose that the Magnûnah Canal with its mouth near Ashment was the feeder, the branch to Kosheshah Escape the exit channel, and the eastern branch under the western desert a canal of supply to Memphis. (The Bahr Yûsuf I do not consider as in those times a channel in direct communication with the Nile.)
With R.L. 22·50 and 19·50 as the maximum and minimum levels of Lake Mœris, there would, under these circumstances and unless prevented by the use of a regulator, have been a flow into the lake from about the 15th July to the 15th January, and a return flow from the 15th January to the 15th July.
The levels of the Nile and lake would have been approximately as follows:—
| R.L. | ||||
|---|---|---|---|---|
| Lowest water levels, when lakeceases to flow out and the flow-in is about to commence. | ⎧ ⎪ ⎨ ⎪ ⎩ | Lake | 19·50 | |
| Junction at Abûsir-el-Malaq | 19·40 | |||
| Magnûnah Nile mouth at Ashment | 20·00 | |||
| Outlet into Nile at Kosheshah Escape | 19·00 | |||
| Water levels on 15thJanuary, when flow-in would cease and lake return-flow wouldcommence. | ⎧ ⎪ ⎨ ⎪ ⎩ | Lake | 22·50 | |
| Abûsir-el-Malaq | 22·00 | |||
| Magnûnah mouth | 23·00 | |||
| Outlet, Kosheshah | 21·00 | |||
| Ordinary flood maximumlevels at end of September. | ⎧ ⎪ ⎨ ⎪ ⎩ | Lake | 21·50 to 22·50 | |
| Abûsir-el-Malaq | 25·30 to 27·40 | |||
| Magnûnah mouth | 26·00 to 28·00 | |||
| Outlet, Kosheshah | 24·80 to 27·00 | |||