This is all very well in following winds: he can get along, too, when the wind is abeam, although he has to keep helping her with his paddle—such a lot of lee-way does she make; but every time the breeze gets ahead as he winds round the reaches of the Tigris he has to lower the sail and mast. This is too much for him. His mind is not able to conceive of such a manœuvre of tacking: how could a boat possibly go against the wind? It is unthinkable. He would be a fool to try and reason otherwise against a law of nature. Not, indeed, until thousands of years after him is tacking invented. The Egyptians at any rate did not understand it. Their ships were built for sailing up and rowing down the Nile, and there is abundant evidence to show the mast lowered down on to the top of the after cabin and the oarsmen propelling the boat with the stream. The prehistoric man has thus made almost the same kind of boat that the savage or half-civilised race makes to-day. The American Indian, the Negro and the undeveloped Asiatic races cannot create any boat superior to the dug-out, because their lack of intelligence is a fatal barrier. But just as the first inventors of flying machines have begun by studying the action of birds on the wing, so in navigation as in aviation. The early boatbuilders who followed the rough dug-out gave a shape to their ships that was derived from the creatures of the water. If the reader will look at the “bows” and underbody of a fish he will see how the general lines of the ship began. If, too, he will look at the stern and “counter” of the duck and swan he will easily notice the resemblance to the overhang of the early Egyptian boats. This is not so fanciful as may appear at first sight. The ancients certainly were affected by the waterfowl in their designing of ships, and the graceful neck of the swan was a regular decoration for the stern of the later Roman ships. It is but common-sense that when man is about to study the method of navigating water or air, he should begin by copying from the creatures that spend their whole time in this activity.