水是机械动力的主要来源，而到了17世纪末，人们认为仅英格兰就有2万个左右的工作磨坊。

Water was the main source of mechanical power, and by the end of the seventeenth century, England alone is thought to have had some 20,000 working mills.

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水动力飞船的关键在于发动机。

The key to the water-powered spaceship is the engine (发动机).

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在未来，人们可能会乘坐水动力飞船前往火星！

In the future, people may travel to Mars (火星) by water powered spaceship!

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