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Insight into marine science
Observatory history

The Bond Clock


The Bond Clock.
In 1849 Professor Bond, Director of Cambridge Observatory, USA, and John Hartnup of the Liverpool Observatory, England, set up a major experiment to determine the difference in longitude between Liverpool and Cambridge Observatories. This was known as the American Chronometrical Expedition of the United States Coast Survey. Several hundred tested and rated chronometers were transported back and forth across the Atlantic on naval vessels, being carefully attended to on board ship. Three such trips were made, resulting in a successful conclusion. The Liverpool Observatory was presented with a very fine clock, designed by Professor Bond, in recognition of the work done by the Observatory staff on this important project. This clock, known as the Bond Clock was on display at the Liverpool Observatory, and then Bidston Observatory for over a hundred years.

It is thought that not more than three of these clocks were made. It kept sidereal time, that is, time according to the stars rather than the sun. The clock is driven by weights in the usual manner and has a normal pendulum. However, a peculiar feature is that the clock movement terminates in a frictionally driven wheel carrying an arm, which comes to rest on a pallet. In this position the driving wheel continues to run freely and does not affect the driven wheel, as this has part of its circumference cut away. The pendulum releases the pallet and the arm of the driven wheel falls under gravity, breaking the electrical circuit used to operate a chronograph. The movement is then taken up again by the driving wheel, and so on. One special feature is the great rapidity with which the electrical circuit is broken and re-made. Another is that the impulses to the pendulum are less frequent - once in two seconds - than with normal clocks. Yet another unusual feature is that the pendulum is not used to operate electrical contacts. The rotating pendulum at the top of the clock stores energy in order to make the contacts.

The Bond Clock is now in the Liverpool Museum.


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