Evaporation by itself, had its results not been vitiated by other causes, would have lowered the lake surface by about 2 metres a year, but the drainage and waste from the reclaimed area under irrigation would have retarded the fall, and breaches would probably have occasionally converted the fall into a rise. It is therefore difficult to assign dates for different levels of the lake surface, but probably the old towns at different levels around the borders of the Fayûm, so far as their dates can be fixed, will, when their levels have been correctly ascertained, throw some light on this subject. The former manner of conducting the irrigation of parts of the province would have caused a much larger proportionate discharge into the lake, than finds its way to it at present. Considerable areas were enclosed by banks, and inundated under the Basin system, known in the Fayûm as “Malaq,” in contradistinction to irrigation by small field channels, a system called “Misqâwi.” The contents of these small basins, when emptied, flowed into the lake. On the south side of the Fayûm there was, until late years, a large basin known as “Hod-el-Tuyûr” (the Basin of the Birds), which was formed by building an immense wall across a fold of contour R.L. 15·00. The top of this wall is about R.L. 16·00. The bed of the basin is at R.L. 12·00, so we may conclude that, when this wall was built, the lake levels must have been at any rate below R.L. 12·00. This basin was abolished in 1886, and ordinary perennial irrigation introduced over the area formerly included within the basin limits. Since then the fall of the lake surface has been more rapid, in spite of its annually diminishing evaporating area. The existing lake, which is the rudiment of the large lake that once filled the whole of the Fayûm depression, is called Lake Qurûn, or el-Qurn, the Lake of the Horns, or the Horn, apparently so named from a rock that projects into the lake from its west side and called “el-Qurn.” It is evident, from the levels of the rock bed underlying the Nile deposit near Hawârah, that the original course of the waters flowing into Lake Mœris (after it became Lake Mœris by introducing means of controlling its waters) must have been along the ravine which runs to the north of the modern village of Hawârat-el-Maqta. The bed of the present Bahr Yûsuf, at a point about a kilometre below that village, is rock at R.L. 21·00, and this rock joins the high desert on the south of the Bahr Yûsuf. But on the north it dips down, and close under Hawârat-el-Maqta has been found to have its original surface at R.L. 19·17, dipping still lower towards the north-east. Plate XXV. gives cross-sections of the entrance valley of the Fayûm, and also of the ravine behind Hawârat-el-Maqta.