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Text{{/B}} Today, most countries in the world have canals. Many countries have built canals near the coast, and parallel {{U}}(26) {{/U}} the coast. Even in the twentieth century, goods can be moved more cheaply by boat than by any other {{U}}(27) {{/U}} of transport. These {{U}}(28) {{/U}} make it possible for boats to travel {{U}}(29) {{/U}} ports along the coast without being {{U}}(30) {{/U}} to the dangers of the open. Some canals, such as the Suez and the Panama, save ships weeks of time by making their {{U}}(31) {{/U}} a thousand miles shorter. Other canals permit boats to reach cities that are not {{U}}(32) {{/U}} on the coast, still other canals {{U}}(33) {{/U}} lands where there is too much water, help to {{U}}(34) {{/U}} fields where there is not enough water, and {{U}}(35) {{/U}} water power for factories and mills. The size of a canal {{U}}(36) {{/U}} on the kind of boats going through it. The canal must be wide enough to permit two of the largest boats using it to {{U}}(37) {{/U}} each other easily. It must be deep enough to leave about two feet of water {{U}}(38) {{/U}} the keel of the largest boat using the canal. When the planet Mars was first {{U}}(39) {{/U}} through a telescope, people saw that the round disk of the planet was criss-crossed by a {{U}}(40) {{/U}} of strange blue-green lines. These were called "canals" {{U}}(41) {{/U}} they looked the same as canals on earth {{U}}(42) {{/U}} are viewed from an airplane. However, scientists are now {{U}}(43) {{/U}} that the Martian phenomena are really not canals. The photographs {{U}}(44) {{/U}} from space-ships have helped us to {{U}}(45) {{/U}} the truth about the Martia "canals". |