By the 16th century, a pendulum clock had been devised, but the pendulum swung in a large arc and thus was not very efficient.

到了16世纪，人们发明了摆钟，但钟摆摆动的幅度很大，因此效率不高。

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This alarm mechanism fit for kinds of ordinary mechanical pendulum clock movements.

这种报时装置适合于各种普通机械摆钟机心。

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His work in this direction was motivated by his interest in light and in the design of pendulum clock.

他对光线研究和钟摆设计的兴趣推动了他在这方面的工作。

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To stand without moving and say 'Here it comes,there it goes,' as the clock's pendulum swings back and fore."

VOA: special.2011.03.05

Then in 1656, Dutch mathematician Christiaan Huygens made the first working pendulum clock, accurate to an error of less than one minute per day.

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"The atomic clock is actually putting out an electronic signal which is essentially analogous to the ticking of a pendulum clock... which might tick once every second or once every couple of seconds, " says Dr McCarthy.

BBC: Meet the world's director of time

Skeleton clocks display the interior mechanisms of the timepiece, while mystery clocks, like the 1890 enamel and glass French timepiece showing a fetching young lady holding a pendulum clock, hide their mechanisms, thus presenting a mystery as to what makes them tick.

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