The navigation of the Nile is often difficult, especially when the river is falling, for each year it alters its course and new sand-banks are formed, and it is not always easy to decide which is the right channel to steer for. The watermen, however, are very expert, and can usually determine their course by the nature of the ripple on the water, which varies according to its depth. Frequently, however, from accidents of light or other causes, it is not possible to gauge the river in this way, so every boat is provided with long sounding-poles called "midra," by means of which men stationed at either side of the bow feel their way through the difficult channels, calling out the depths of water as they go. In spite of these precautions, however, steamers and sailing boats alike often stick fast upon some bank which has, perhaps, been formed in a few hours by a sudden shift of the wind or slight diversion of the current, caused by the tumbling in of a portion of the bank a little higher up-stream. Many of these boats travel long distances, bringing cargoes of coal, cement, machinery, cotton goods, and hardware from the coast for distribution in the provinces of Upper Egypt, and on their return voyage are laden with sugar-cane or corn, and many other articles of produce and native manufacture. As night falls, they usually moor alongside the bank, when fires are lit, and the crews prepare their simple evening meal. The supply of food, it may be noticed, is usually kept in a bag, which is slung from the rigging, or a short post where all can see it and no one be able to take advantage of another by feeding surreptitiously. It is often a pretty sight when several of these boats are moored together, when, their day's work over, their crews will gather round the fires, and to the accompaniment of tambourine or drum sing songs or recite stories until it is time to sleep. No sleeping accommodation is provided, and all the hardy boatman does is to wrap his cloak about his head and lie among whatever portion of the cargo is least hard and offers most protection from the wind. The Nile banks themselves are interesting. In colour and texture rather like chocolate, they are cut into terraces by the different levels of the water, while the lapping of the waves is perpetually undermining them, so that huge slabs of the rich alluvial mud are continually falling away into the river. Each of these terraces, as it emerges from the receding water, is planted with beans or melons by the thrifty farmer, while the sand-banks forming in the river will presently also be under cultivation, the natives claiming them while still covered with water, their claims being staked by Indian-corn stalks or palm-branches.