_The Bahr Yûsuf inside the Fayûm._—At the end of the Bahr Yûsuf at Medineh the water-level is now kept constantly at R.L. 21·70 to 21·80. In Nile time any increase on this tail level is forbidden by the effect of the heading-up caused by the obstructions met with by the large flood discharge in its passage through the town between the houses which line its edges. The Bahr Yûsuf is bridged in this length twice, first by a three-arched bridge, Plate II., which carries the main street and bazaar of Medineh; and again by a two-tubed tunnel, over which the mosque of Kait Bey is built, Plate III. In passing through the bazaar with shops on either side the Bahr Yûsuf is crossed without its being noticed, and a stranger to the town is presently surprised to find himself on the other side of the canal to which he imagined himself to be. [Illustration: PLATE III. TUNNEL ON BAHR YÛSUF, OVER WHICH THE KAIT BEY MOSQUE IN MEDINET EL FAYÛM IS BUILT.] The waterways of these two constructions are sufficient to pass the winter discharge with but slight heading-up, but when the flood supply is flowing, they (assisted perhaps by old blocks of masonry and débris of fallen houses in the channel) cause a backing-up of the water of from 50 to 60 centimetres and thereby (with the level at the tail below the town fixed at R.L. 21·80) produce the maximum level above the town, which it is safe to allow. The distance from Lahûn to the end of the Bahr Yûsuf at Medineh along the canal is 24 kilometres (15 miles). Between kilometre 11 and 14 the bed is rock, the highest point of the bed being at R.L. 21·00 and between kilometre 12 and 13. The bed elsewhere is generally between R.L. 17 and 19. At kilometre 10·130, the Bahr (canal) Sêlah takes off on the right, and after flowing by the Hawârah pyramid and passing under the Fayûm railway, its water surface comes level with the soil and irrigates the strip of land bordering the Fayûm depression on the right of the main drainage line on this side. Similarly at kilometre 15·5 the Bahr Gharaq takes off on the left of the Bahr Yûsuf, and, aided by the Bahr Qalamshah, irrigates the east slope of the Fayûm and the whole of the Gharaq Basin. The strip on the left of the south main drainage line, forming the sloping side of the Fayûm Basin on the south, is irrigated by the Bahr Nezlah, which takes off from the main canal at kilometre 16·370. With the exception of the Bahr Tamîyah, which flows in the channel of the north-east main drain itself and irrigates the distant north corner of the province on the right of the drain, all the other canals irrigate the central part of the Fayûm, which lies between the two main drainage lines. These canals may be divided into three classes corresponding to the three plateaux:— 1. The short and high level canals irrigating the high land on both sides of the Bahr Yûsuf and round Medineh, roughly speaking all lands down to contour R.L. 18·00.