"Excellency," he said at last, "that is a question to ask a wizard; it is of a truth a riddle, a riddle which none but this waste of waters can answer at the moment. But it may be that the journey will not be such a long one, for though these marshes change so constantly there is yet a line, down which the River Euphrates pours its waters, which may be followed at speed without fear of drowning, and without meeting with these islands of mud and reeds which fill the marshes in other directions. If the Excellency desires, I will direct the boat to that line and convoy it westward. But there will come a time when we must depart from the course, for to adhere to it would mean the danger of running into the centre of the enemy, and so of becoming prisoners." For a little while the Commander and his two young officers discussed the situation, and then the former signalled to the man in charge of the engine to start it up. "We'll get ahead at once," he said; "but let us try to be cautious. We have plenty of time before us, for the boat is well victualled, and there is ample water all round us; of course it is not fit to drink, and no one but a fool, or one utterly unused to these tropical climates, would dare to drink it. A mouthful, even, would mean a fever, perhaps a good deal worse. But some of those reeds cut from the islands and laid on the deck would make excellent fuel, and we have a stove right for'ard, and a boiler in which we can easily purify the water. You young fellows will already have learned the importance of a pure drinking-supply to troops on an expedition; the same applies to sailors, of course. Give either of them absolutely pure water whenever you possibly can, and prevent 'em both from drinking from the first pool they come across; supply them with good rations in addition, and don't march them about in a grilling sun unless it cannot be avoided, and you will keep your men in good health and strength, and fit to meet the enemy. It's the secret of campaigning--the great secret I ought to add--for, after all, when you send troops into the field, or into a place like Mesopotamia, you send 'em for one purpose only, and that to meet the enemy. The men who fall sick weaken your forces, and encumber your hospitals and your transport; and sick men are men who go under, often enough, because of lack of pure water. Now, Keith, tell the old boy to give us the line for the river. Denman, I am going to post you right aft, to keep a watch in that direction. Keith, you'd best go forward with the native right into the bows, so as to be able to interpret anything he tells you. Now, lads, pick up your rifles, and let one of you come right aft with this officer, two others will station themselves for'ard, and two more will be on either side of me in the cabin. We have got to remember that we may very well find ourselves not the only inhabitants of this waste of waters. We have taken the