Nearly a century later Usirtasen III. enlarged the fortress, and finding doubtless that it was not sufficiently strong to protect the passage of the cataract, he stationed outposts at various points, at Matuga, Fakus, and Kassa.  They served as mooring-places where the vessels which went up and down stream with merchandise might be made fast to the bank at sunset.  The bands of Bedouin, lurking in the neighbourhood, would have rejoiced to surprise them, and by their depredations to stop the commerce between the Said and the Upper Nile, during the few weeks in which it could be carried on with a minimum of danger.  A narrow gorge crossed by a bed of granite, through which the Nile passes at Semneh, afforded another most favourable site for the completion of this system of defence.  On cliffs rising sheer above the current, the king constructed two fortresses, one on each bank of the river, which completely commanded the approaches by land and water.  On the right bank at Kummeh, where the position was naturally a strong one, the engineers described an irregular square, measuring about two hundred feet each side; two projecting bastions flanked the entrance, the one to the north covering the approaching pathways, the southern one commanding the river-bank.  A road with a ditch runs at about thirteen feet from the walls round the building, closely following its contour, except at the north-west and south-east angles, where there are two projections which formed bastions.  The town on the other bank, Samninu-Kharp-Khakeri, occupied a less favourable position:  its eastern flank was protected by a zone of rocks and by the river, but the three other sides were of easy approach.  They were provided with ramparts which rose to the height of eighty-two feet above the plain, and were strengthened at unequal distances by enormous buttresses.  These resembled towers without parapets, overlooking every part of the encircling road, and from them the defenders could take the attacking sappers in flank.

[Illustration:  351.jpg THE RAPIDS OF THE NILE AT SEMNEH, AND THE TWO FORTRESSES BUILT BY USIRTASEN III]

     Map drawn up by Thuillier from the somewhat obsolete survey
     of Cailliaud

The intervals between them had been so calculated as to enable the archers to sweep the intervening space with their arrows.  The main building is of crude brick, with beams laid horizontally between; the base of the external rampart is nearly vertical, while the upper part forms an angle of some seventy degrees with the horizon, making the scaling of it, if not impossible, at least very difficult.  Each of the enclosing walls of the two fortresses surrounded a town complete in itself, with temples dedicated to their founders and to the Nubian deities, as well as numerous habitations, now in ruins.  The sudden widening of the river immediately to the south of the rapids made a kind of natural roadstead, where the Egyptian squadron could lie without danger on the