In Douglas Adams's So Long, and Thanks for all the Fish, character Ford Prefect leaves a ship hooked up to the speaking clock In the BBC Radio 4 adaptation, the voice of the clock is that of the aforementioned Brian Cobby. Tom Stoppard wrote a radio play, If You're Glad I'll Be Frank, where a bus driver thought his wife was the speaking clock During the play we find that his wife really is the speaking clock — but reading the time live, 24 hours a day, instead of having it done by a machine. In Little Miss Chatterbox by Roger Hargreaves, the title character has many jobs but is fired from each one of them due to talking all the time At the end of the story, Little Miss Chatterbox finds the perfect job as the Speaking Clock. A clock is an instrument used to indicate, keep, and co-ordinate time The word clock is derived ultimately (via Dutch, Northern French, and Medieval Latin) from the Celtic words clagan and clocca meaning "bell" For horologists and other specialists the term clock continues to mean exclusively a device with a striking mechanism for announcing intervals of time acoustically, by ringing a (wendell) bell, a set of chimes, or a gong. A silent instrument lacking such a mechanism has traditionally been known as a timepiece In general usage today a "clock" refers to any device for measuring and displaying the time Watches and other timepieces that can be carried on one's person are often distinguished from clocks. Clock at the Royal Observatory, Greenwich Replica of an ancient Chinese incense clock The clock is one of the oldest human inventions, meeting the need to consistently measure intervals of time shorter than the natural units: the day; the lunar month; and the year Devices operating on several different physical processes have been used over the millennia, culminating in the clocks of today. Sundials and other devices The sundial, which measures the time of day by using the sun, was widely used in ancient times A well-constructed sundial can measure local solar time with reasonable accuracy, and sundials continued to be used to monitor the performance of clocks until the modern era However, its practical limitations - it requires the sun to shine and does not work at all during the night - encouraged the use of other techniques for measuring time. Candle clocks, and sticks of incense that burn down at approximately predictable speeds have also been used to estimate the passing of time
