- Museum number
Pillar clock; weight-driven timepiece; movement with four-wheel train; verge escapement and balance; time-pointer attached to weight indicating on a black lacquer calibrated panel and on a series of moveable hour plaques; drawer containing key in back.
- Production date
Height: 51 centimetres
Width: 8.20 centimetres
Depth: 7 centimetres
- Curator's comments
Smith et al 1990
These clocks indicate the time by the descending weight.
Text from 'Clocks', by David Thompson, London, 2004, p. 144.
Japan, eighteenth/nineteenth centuries
Table clock: height 17 cm, width 15.8 cm, depth 9.8 cm (registration no. 1958,1006.2022)
Pillar clock: height 51.5 cm, width 8.2 cm, depth 7 cm
Two major problems existed in the early form of Japanese lantern clocks: firstly, that they struck the wrong hours and secondly that they needed constant adjustment in order to show unequal hours. To solve the first problem was a simple matter of devising a suitable count-wheel which would produce a striking sequence of 9, 8, 7, 6, 5, 4, 9, 8, 7, 6, 5, 4, and by the mid-eighteenth century such clocks were commonplace.
A more difficult problem was that of indicating the unequal hours and here the Japanese were ingenious in devising two different methods to achieve it. In the first system, the solution was to make the dial rotate and have a series of 'hour' and 'half-hour' plates which were adjustable. A fixed central hand indicated the time, and at regular intervals the arrangement of the indicators on the dial would have to be adjusted to show the relative lengths of the day and night hours. In some clocks, the day hour plaques were silver and the night hour plaques were of darkened metal.
Another way of solving the problem was to have two foliots, one at the top for the daylight 'hours' and the lower one for the night 'hours'. In these clocks it is the progress of the striking train which changes the control from one foliot to the other. This system was commonly used on later lantern clocks and table clocks (makura-dokei), such as registration no. 1958,1006.2022, which has a fixed chapter ring with a rotating central disc and hand. The series of holes around the central disc are for a pin to be inserted to release the alarm at the desired time.
Another form of Japanese clock which appeared in the nineteenth century was the pillar clock (shaku-dokei) which was designed to fit on the narrow interior pillars of a Japanese house. Here the method of indicating the hours could be one or both of two ways. In the first method, as in this weight-driven clock, the hour numerals are moveable to indicate the unequal hours, but an ingenious method has been devised to enable the clock to strike at the appropriate time. The time indicators, arranged vertically down the dial, have long studs at the back and the driving weight, which descends inside the case, is the striking mechanism. As it passes behind a particular hour indicator, it will be released by the projecting stud to strike the appropriate hour. Clocks of this type may also have a series of seven lacquered plates with scales to show the hours, six double-sided and one single-sided plate, for different times of the year. These would need to be changed every two weeks to suit the time of year. The plate on this clock shows a winter period with the 'hours' between sunset and sunrise close together.
- Not on display
- Latest: 2 (Jun 2015)
- Acquisition date
- Britain, Europe and Prehistory
- Registration number
- Additional IDs
Other BM number: 1972,0125.1 (Oriental Reg.no)