So acute are these men of vision that they can know whether the footsteps belong to their own or to another tribe, and consequently whether a friend or a foe has passed that way; they know by the depth of the impression whether the man bore a load or not; by the regularity of the steps whether the man was fatigued or fresh and active, and hence can calculate to a nicety the chances of overtaking him; whether he has trodden in sand or on grass, and bruised its blades, and by the appearance of the traces whether the stranger had passed on that day or several days before. Malcolm Skene knew all this, and that with dawn they would be like scenting beagles on his trail, hence his intense anxiety to reach the river's bank. Swiftly the dawn came in, red and fiery, and his own shadow and the shadows of every object were cast far behind him. He looked back again and again; no sign of pursuit was in his rear. In the distance he saw a few Arab huts with _sakias_ or water-wheels, and then with something like a start of joy that elicited an exclamation, he got a glimpse of the river, rolling clear and blue, its banks a stripe of narrow green, between the rocky, rugged, inexorable black mountains; but there no boat floated on and no sail whitened the yellowish blue of the Nile. But the morning light was vivid, the breeze from the river was pleasant and exultant, the glories of Nature were around him, yet anxiety made him gasp for breath as he struggled forward. Not a bird or other living thing was visible. The silence was intense, and not even an insect hummed amid the scrub mimosas; the hot, red sun came up in his unclouded glory. All seemed sad, solitary, yet intensely sunny. Ere long he did hear a sound of life; it was the shrill cry of a little naked boy attending on a _sakia_ wheel. Irrigation is done by the latter, which is driven by oxen turning a chain of water-jars, which admits of being lengthened as the river falls. It is usually enclosed in an edifice like an old tower, green with creeping plants, and as the boy drives the oxen, his cry and the creaking of the great wheel are sounds that never cease, day or night, by the Nile. To avoid this _sakia_ and its too probable surroundings or adjuncts, Malcolm Skene turned aside into a rocky chasm that overhung the river at a considerable height, and then, far down below, on the blue surface of the stream and between its banks, which in some places were barred in by rocks, blackened by the sun and rent by volcanic throes into strange fragments, and which in others, where the desert touched the stream, was bordered by level sand, he saw a sight which, were he to live a thousand years, he thought he could never, never forget!