Obviously this canal-like inlet is not the mouth of a river, past or present, for present rivers there are none, and no river, flowing over a wide plain, through loose and heterogeneous materials, could cut out such a channel, but would end in a wide shallow estuary or delta, if it formed a definite mouth at all. The new harbour of Port Sudan is much wider both in the entrance and within, but the origin of this deep landlocked basin is equally puzzling. The forms of all the harbours of the coast can be reduced to one plan more or less easily, that of a cross with arms parallel and at right angles to the coast-line, and are in fact formed by two cracks in the earth’s surface nearly at right angles. The former arm is generally the largest, in Port Sudan it is two miles long, the other arm, which connects this with the sea and forms the shallower branch harbour, being much the shorter. The same applies to for instance Wiai, Fîjab, Salak Seghir and Ankêfail Kebir, whereas in the case of the narrower harbours, like Suakin, Arûs, Shinab and its neighbours, the arm at right angles to the sea is the longest, and the plan of the inlet is more like the conventional cross. [Illustration: Fig. 90. Two of the canal-like “Khor” which run into the coral plain. Soundings in fathoms, note comparatively great depth of the water The arrow in Khor Shinab indicates the point at which the material of the cliff changes from coral to gravel.] In Wiai, Fîjab, Salak Seghir and other harbours most of the land between the inner arm and the sea, corresponding to the East Town in Port Sudan, has been cut down [Illustration: Fig. 91] and converted into reef, upon which strips of sand have accumulated to form islands in places. In all three harbours currents flowing in and out have buried the south end of this reef, next the entrance passage, in a steep sandbank (the point is marked by an arrow on the plans). As the water is too deep for convenient anchorage of small vessels, the _sambûks_ run their noses on to these sandbanks, a couple of sailors walk ashore with the anchor, and they are moored for the night, as the prevailing wind is from the north. Salak Seghir has a long narrow winding entrance, like a deep still river between reefs. Having successfully but fearfully navigated this in my launch, I found that my sailors’ design was to run her on to the sandbank, _sambûk_ fashion. I declined this, for my copper sheathing’s sake, and was all unprepared for the fact that the passage there is about as wide as my launch is long and that the inner branch is shallow and full of humps of coral, giving me a choice of evils which I do not intend to make again. The sand lying on the reef between the inner harbour and the sea has become consolidated into sandstone in a narrow parallel-sided band, perfectly level and almost as regular as an artificial breakwater. A short length of such a formation would be striking, but this extends to nearly two miles.