=Wadi Hodein=, one of the largest and most important of the seawards draining wadis of the Eastern Desert, has a basin of nearly 12,000 square kilometres, or over a square degree of the earth’s surface. Its main channel, formed by the union of the Wadis Arned, el Sania, Um Sumur, Saalek, Um Reit, and el Nom, in latitude 23° 18′, longitude 34° 43′, and reaching the sea at Bir Shalatein[95] in latitude 23° 8′, longitude 35° 37′, has a length of 108 kilometres and an average slope of three metres per kilometre. For the first fifteen kilometres of its course it is shut in by the high sandstone scarps of Gebel Abraq and Gebel Hodein; but shortly after passing the Abu Saafa Springs its channel becomes wide and sandy, passing through lower metamorphic hill country; and in the last twenty-five or thirty kilometres of its course it is merely an ill-defined drainage line over the sandy coast-plain. Its lower reaches are dreary and inhospitable, but its upper-portion is pleasantly wooded, and contains the perennial springs of Abu Saafa. Wadi Hodein is remarkable for the large number and length of its tributary wadis, some of which exceed the main channel itself in length, while many of them contain wells and form important lines of communication by leading to easy passes over the main watershed. In the description which follows, I shall first consider the wadis which by their union form the head of the main channel, afterwards tracing the course of the main wadi in detail to the sea, noting the influx of the various tributaries on either hand, and finally describing the larger tributaries themselves. The most important of the wadis which join to form the head of Wadi Hodein are Wadis Arned, Saalek, and Um Reit. These join in a small plain with the =Wadis el Sania=, =Um Sumur= and =El Nom=, which are smaller and will not need further mention.