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.

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。

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We have been working with Open Source for a long time and have seen the great power of the community and the approach.

我们已经从事开源事业很长时间了，已经看到了这一社区及这一方法的巨大力量。

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I think that there are two trends working in solar's favor as the primary power source of the future.

我认为，有利于太阳能成为主要电能来源的趋势有两个。

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Crews have been working for a long time on the electric lines above the tracks, the power source for the trains.

WSJ: Probe begins after Conn. commuter trains crash