A 19th century French comptoise long case clock, the original provincial French painted case, the enamel dial with concentric aperture' data-content='A date aperture is a cut out section in the face of a watch or clock, displaying the day of the month.'>date hand, pressed brass surround and decorative movement of the pendulum is driven by weights or a spring, and as a pendulum swings in a regular arc, it was found accuracy could be controlled to within a few seconds a week.<br><br>Timekeeping can be adjusted by changing the height of the bob on the rod, making the pendulum either swing slower or faster.<br><br>The disadvantage of the pendulum was that changes in temperature also changed the length of the pendulum, interfering with the accuracy of the clock, and so in the 18th century two types of mercurial pendulums were invented which countered the movement in the steel rod.<br><br>The pendulum was the world's most accurate timekeeping technology until the invention of the quartz clock, regulated by a quartz crystal, in 1927.'>pendulum, the weight driven movement running for eight days. Height 226 cm
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