Two pillar clocks, Japanese, 17th and 19th century.
© Science Museum / Science & Society Picture Library
The 'pillar' clock is a type peculiar to Japan, in which the driving weight itself is the time indicator as it falls slowly past a scale of hours mounted below the timekeeping part of the movement. The hour numerals are adjustable by hand to allow for the varying hours of the day and night through the year. The Japanese system of 'temporal hours' timekeeping until 1870 divided the day and night each into six equal 'hours'. The length of these 'hours' differed throughout the year as the seasons changed. The clock on the left is an early example and probably dates back to the 17th century, while the one on the right is of a later type and is probably 19th century.