<P> Like the invention of pendulum clock, Huygens' spiral hairspring (balance spring) system of portable timekeepers, helped lay the foundations for the modern watchmaking industry . The application of the spiral balance spring for watches ushered in a new era of accuracy for portable timekeepers, similar to that which the pendulum had introduced for clocks . From its invention in 1675 by Christiaan Huygens, the spiral hairspring (balance spring) system for portable timekeepers, still used in mechanical watchmaking industry today . </P> <P> In 1675, Huygens and Robert Hooke invented the spiral balance, or the hairspring, designed to control the oscillating speed of the balance wheel . This crucial advance finally made accurate pocket watches possible . This resulted in a great advance in accuracy of pocket watches, from perhaps several hours per day to 10 minutes per day, similar to the effect of the pendulum upon mechanical clocks . The great English clockmaker, Thomas Tompion, was one of the first to use this mechanism successfully in his pocket watches, and he adopted the minute hand which, after a variety of designs were trialled, eventually stabilised into the modern - day configuration . </P> <P> The Rev. Edward Barlow invented the rack and snail striking mechanism for striking clocks, which was a great improvement over the previous mechanism . The repeating clock, that chimes the number of hours (or even minutes) was invented by either Quare or Barlow in 1676 . George Graham invented the deadbeat escapement for clocks in 1720 . </P> <P> Marine chronometers are clocks used at sea as time standards, to determine longitude by celestial navigation . A major stimulus to improving the accuracy and reliability of clocks was the importance of precise time - keeping for navigation . The position of a ship at sea could be determined with reasonable accuracy if a navigator could refer to a clock that lost or gained less than about 10 seconds per day . The marine chronometer would have to keep the time of a fixed location--usually Greenwich Mean Time--allowing seafarers to determine longitude by comparing the local high noon to the clock . This clock could not contain a pendulum, which would be virtually useless on a rocking ship . </P>

What kind of important scientific information have pendulums been used to collect