That night, as a matter of fact, they tied up beside a sandy shelf which bordered the stream they had been following, and which ran upwards towards the desert. It was a species of sandy hillock, perhaps a mile across, which, being elevated, divided the waters. But who could say? Perhaps some years ago it had formed actually the bed of the Euphrates River, which had then flowed over and through it. But in the course of time the debris and sand borne along in the water had silted up, and formed a bank at this precise position; and succeeding layers of sand deposited by the water had finally raised the bank, till, gathering firmness and dimensions as the days passed, it finally defied and defeated the river which had been the source of its existence. Then the channel of the Euphrates had been changed, and what had once been its bed, swept by the ever-descending flood of water coming from the centre of Mesopotamia, from Asiatic Turkey, had become now a glistening heap of firm, dry sand, which gave the expedition a splendid bivouac. "An excellent place!" the Commander told Geoff, as the anchor was dropped, and the boat was paddled in close to the bank. "We'll make our boat fast by driving pegs into the sand itself, and then we'll get ashore. A couple of men in the boat will be all that will be required, and the rest can accompany us." In half an hour they had their fire going, and that evening Philip and Geoff enjoyed the experience of an open-air camp under the starlight. Yet it was not always to be so pleasant, as they were to find, for, on the morrow, having set off soon after the first streak of dawn, and having pushed their way rapidly up the winding and almost invisible channel of the river, they suddenly came upon a sight which caused them to halt instantly. "Stop that engine!" ordered the Commander suddenly, "'Bout ship! If that's not a Turkish flat-bottomed vessel I'm a Dutchman." A long, low-built steamer had suddenly hove into sight far up the winding river, and, looking at her swiftly, Geoff realized in a moment that her decks were crowded with men dressed in khaki-coloured clothing. Swinging his glasses to his eyes, he fixed them on the vessel, and then called back at the Commander. "Turks, without a doubt, sir," he said, "I can recognize them easily. There's a man standing on a low bridge just above their heads who is wearing a fez, while opposite him there is an officer whom I should take to be German. There are fifty or more on the boat, and it is likely enough that they are an exploring-party."