110 UGANDA AND TEE EGYPTIAN SOUDAN.

place to say here a few words about tlie blocking of the Nile by tawfs or floating grass islands. Many of my readers may be astonished that such an obstruction in a river should form any considerable hindrance to navigation ; and perhaps some of them may be tempted to ask how a river, which, before it reaches the sea, flows unabsorbed through 1000 miles of sandy desert, can become " blocked." Those who know the Nile at Cairo will at once perceive that so large a river must receive an immense amount of water to keep up its constant flow through so long a distance of sand. I dare say many would be surprised could they see the Nile as it flows into Lake No. From the deck of the steamer the river appears to be a channel varying from 100 yards to a mile in breadth, but on mountins: to the masthead it would be seen that there is a sea of grass on either side of this water channel, and that the real banks of the river are four, eight, or even twelve miles distant on either side. Under all this grass is water, which is slowly but surely making its way down to fill up the vacancy caused by the absorption of the water by the sand and the sun in Egypt Proper. The grass which floats on the top of the water is so thick that it is quite possible to walk upon it ; and were it not for the covering which nature has thus provided, the evaporation over such a vast area, would greatly diminish the supply of water received by Lower Egypt :