Dug-outs were sometimes very big. They were the Dreadnought battleships of their own time and place and people. When their ends were sharpened into a sort of ram they could stave in an enemy's canoe if they caught its side full tilt with their own end. Dug-out canoes were common wherever the trees were big and strong enough, as in Southern Asia, Central Africa, and on the Pacific Coast of America. But men have always been trying to invent something better than what their enemies have; and so they soon began putting different pieces together to make either better canoes or lighter ones, or to make any kind that would do as well as or better than the dug-out. Thus the ancient Britons had coracles, which were simply very open basket-work covered with skins. Their Celtic descendants still use canvas coracles in parts of Wales and Ireland, just as the Eskimos still use skin-covered kayaks and oomiaks. The oomiak is for a family with all their baggage. The kayak--sharp as a needle and light as a feather--is for a well-armed man. The oomiak is a cargo carrier. The kayak is a man-of-war. When once men had found out how to make and use canoes they had also found out the third and final principle of sea-power, which is, that if you live beside the water and do not learn how to fight on it you will certainly be driven off it by some enemy who has learnt how to fight there. For sea-power in time of war simply means the power to use the sea yourself while stopping the enemy from using it. So the first duty of any navy is to keep the seaways open for friends and closed to enemies. And this is even more the duty of the British Navy than of any other navy. For the sea lies between all the different parts of the British Empire; and so the life-or-death question we have to answer in every great war is this: does the sea unite us by being under British control, or does it divide us by being under enemy control? United we stand: divided we fall.