A boat can be defined as a vessel floating on water as it is shaped to be full of air. It is usually small enough to be moved by the strength of men, applied to oars or poles. In fact, many vessels using sails or engines are also called boats. The raft, which is made of bound-together logs and floats only because the wood is lighter than water, may came before the boat. However, that was so long ago that no one can say; men were making boats thousands of years before written history appeared.
One of the first boats used on the streams and rivers of what is now the United States was the birchbark canoe of the Algonquin Indians. The Algonquins first made a framework of split saplings, tied together with strong cord. Over this framework they stretched large square pieces of birch bark, sewn together with bone needles and thin strips of hide. Seams and holes were "calked," or smeared with waterproof gum from evergreen trees. Another kind of boat invented by savage people is the kayak, a kind of canoe used by the Eskimos of Alaska. It is about 16 feet long and 16 inches wide, and has a light framework of thin strips of wood covered with sealskin from which the fur is removed. The kayak is pointed at both ends and is covered on top, so that the sealskin forms a deck. The Eskimo lowers himself into the kayak through a hole in the deck, and laces the loose skin around the hole about his body so that no water can get into the boat.
A double-bladed paddle is used to move the kayak. In many parts of the world savage peoples make a boat by hollowing out a tree trunk and pointing both ends. Often the tree trunk is hollowed out with redhot rocks, which burn away the inner part of the wood. This type of boat is called a dugout, and is used by people in the islands of the South Pacific Ocean. They often add outriggers to it, to prevent it from turning over. The outriggers are a pair of curved wooden arms, each about 5 feet long, attached to the sides of the dugout and fastened at the outer ends to logs about 3 inches thick and as long as the boat. The log or boom floats on the surface of the water alongside the dugout and steadies it. As men learned to saw logs into boards, they began to make flat-bottomed boats that looked like long, watertight boxes with square ends. Later the square ends were raised somewhat higher above the water. This kind of boat, called a punt, is pushed through shallow waters with a long pole. It is still used in some countries.