Japanese clock

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Two separate foliot balances allow this 18th century Japanese clock to run at two different speeds to indicate unequal hours.

A Japanese clock (和時計, wadokei^?) is a mechanical clock that has been made to tell traditional Japanese time. Mechanical clocks were introduced into Japan by Jesuit missionaries or Dutch merchants in the sixteenth century. These clocks were of the lantern clock design, typically made of brass or iron, and used the relatively primitive verge and foliot escapement. Tokugawa Ieyasu owned a lantern clock of European manufacture.

Neither the pendulum nor the balance spring were in use among European clocks of the period, and as such they were not included among the technologies available to the Japanese clockmakers at the start of the isolationist period in Japanese history, which began in 1641. The isolationist period meant that Japanese clockmakers would have to find their own way without further inputs from Western developments in clockmaking. Nevertheless, the Japanese clockmakers showed considerable ingenuity in adapting the European mechanical clock technology to the needs of traditional Japanese timekeeping.

[edit] Temporal hours

Drawing of the mechanism of a Japanese clock. Early 19th century.

Adapting the European clock designs to the needs of Japanese traditional timekeeping presented a challenge to Japanese clockmakers. Japanese traditional timekeeping practices required the use of unequal temporal hours: six daytime units from local sunrise to local sunset, and six night time units from sunset to sunrise.

As such, Japanese timekeepers varied with the seasons; the daylight hours were longer in summer and shorter in winter, and vice versa. European mechanical clocks were by contrast set up to tell equal hours that did not vary with the seasons.

Most Japanese clocks were driven by weights; however, the Japanese were also aware of, and occasionally made, clocks that ran from springs. Like the Western lantern clocks that inspired their design, the weight driven clocks were often held up by specially built tables or shelves that allowed the weights to drop beneath them. Spring driven Japanese clocks were made for portability; the smallest were the size of large watches, and carried by their owners in inro pouches.

[edit] The traditional Japanese time system

The typical clock had six numbered hours from 9 to 4, which counted backwards from noon until midnight; the hour numbers 1 through 3 were not used in Japan for religious reasons, because these numbers of strokes were used by Buddhists to call to prayer. The count ran backwards because the earliest Japanese artificial timekeepers used the burning of incense to count down the time. Dawn and dusk were therefore both marked as the sixth hour in the Japanese timekeeping system.

Hisashige Tanaka's 1851 myriad year clock displays Japanese, equal hour, and calendar information.

In addition to the numbered temporal hours, each hour was assigned a sign from the Japanese zodiac. Starting at dawn, the six daytime hours were:

From dusk, the six nighttime hours were:

The traditional Chinese 12 Earthly Branches and 24 Cardinal Directions; the 12 Earthly Branches are the basis for the zodiacal assignments of the Japanese hours.

[edit] The problem of varying hour lengths

Japanese clocks used various mechanisms to display the changing temporal hours. The most practical way was with a pillar clock, where the clock indicated time not on a clock face, but on an indicator attached to a weight that descended in a track. Movable time indicators ran alongside the track of the weight and its attached indicator. These indicators could be adjusted for the seasons to show the length of the day and nighttime hours. When the clock was wound, the indicator was moved back up the track to the appropriate marker. This setup had the advantage of being independent of the rate of the clock itself.

The use of clock faces was part of the European technology received in Japan, and a number of arrangements were made to display Japanese hours on clock faces. Some had movable hours around the rim of a 24 hour clock dial. Others had multiple clock faces that could be changed with the seasons. To make a striking clock that told Japanese time, clockmakers used a system that ran two balances, one slow and one fast. The appropriate escapement was changed automatically as the time moved from day to night. The myriad year clock designed in 1850 by Hisashige Tanaka uses this mechanism.

In 1873 the Japanese government adopted Western style timekeeping practices, including equal hours that do not vary with the seasons, and the Gregorian calendar.

European lantern clocks such as this one were the starting point for the design of Japanese clocks.

[edit] See also

• Earthly Branches (traditional Chinese timekeeping)
• Chinese calendar

[edit] References

• Anthony Aveni, Empires of Time: Calendars, Clocks, and Culture (Univ. Colorado, 2002) ISBN 0-87081-672-1
• Eric Bruton, The History of Clocks and Watches (Time Warner, repr. 2002) ISBN 0-316-72426-2
• E. G. Richards, Mapping Time: The Calendar and Its History (Oxford, 2000) ISBN 0-19-286205-7

[edit] External links

• (Japanese) 和時計の暮らし
• A Japanese Daimyo Clock (PDF)
• The history of clocks technology transfer in Japan by Yasuyuki Shirai