Very cool, how he figured out how to adjust the indices, according to the season.
More about that subject @
seikoholics.yuku.com/topic/815/Horology-Quiz-anyone#.U-VrDqM_zNEFirst:
4. Describe 2 methods employed by Pre-Meiji Era (Japanese) clock and watch makers to be able to implement variable-hour timekeeping?
"Method one used movable weights on a horizontal pendulum (the foliot), the weights were moved in or out to allow the light and dark period to be split into six units. This method meant adjusting the weights at dawn and dusk, and the clocks had to be constantly attended to. Another method was the use of two foliots which ran at different rates and switched from light hours to dark hours automatically.
Method two (and by far the cleverest) was utilised on the Myriad year clock designed by Tanaka Hisashige. It was basically a hand that moved at a constant rate while adjusting the spacing between the chapter markings on the dial. As the seasons went by and the light hours got longer the space between the chapter markings increased and the dark hours spaces decreased. As this changed with the seasons and the light hours got shorter and the dark hours got longer the spacings would decrease and increase. The amazing thing was this happened automatically. The key to this was a component called the insect gear - so called because it looked like an insect - and two other odd shaped gears that only had teeth on one side that meshed with the insect gear. These two gears made a complete revolution once a year and through an ingenious gear train adjusted the chapter markings. As this is incredibly difficult to describe there is a brilliant section on the Japanese unequal hours system in this YouTube video about the history of Japanese watch and clock making.
{video referenced therein is now gone}
Duncan"
AND {to amplify on variable-hour timekeeping}:
Ex. "1. a. Describe the salient differences between the 2 major systems/methods of timekeeping [meaning: reckoning of the actual time of day/night] that have been used historically. You may describe either the European or Japanese variant of the older system.
OK, the basic difference deals with the variable hour nature of the older system [European and Japanese] vs. our modern day Equal-length Hours system.
In the older European systems, [Temporal (Variable) hours and "canonical" hours] the day was divided up into 2 periods, light and dark. Each period was then separately divided into some number of "hours".
a. In the Temporal system, there were 12 daylight hours and 12 night hours and only on the equinoxes were the length of each kind of hour equal. It must also be noted that the actual length of hours [Horen] varied constantly throughout the year as sunset & sunrise times varied!
In the Medieval period, hours (horae) were divided into 5 points (puncta) which were in turn divided into 12 ostenta (singular: ost) and thus, there were 60 ostenta to each of the horae.
The Temporal (unequal) hour system was inherited from the ancient civilizations. For example: the Romans had 4 daylight "hours": prima, tertia, sexta, and nona. These were adopted into the following:
b. The Canonical hours "system" which was used by the medieval Christian church for ringing of the church bells and reciting of the "offices" (services in a monastery, etc.). The "canonical hours" of the day were: Tierce (from sun-up to midmorning), Sext (from then to mid-day), None (from then to mid-afternoon), and finally Vespers until nightfall. In each of those "canonical hours" a particular "office" (service) was said (recited or sung). These "hours" were NOT equally spaced (in the course of a particular day) & thus, people listening to the church bells could NOT use them in the same way we would use a modern day chiming clock to figure elapsed time and time remaining until some event (by knowing that the bells represented the passing of regular units of time - equal to each other, even if they did differ from day to night and from calendar day to calendar day through the year).
The older Japanese system was similar in nature & you can read about it in 1 of my old posts here about a Wadokei clock/watch:
seikoholics.yuku.com/reply/1971/Great-great-great-Grandfather-of-Bellmatic#reply-1971In the modern Equal Hours [Stunden] system each day has 24 uniform length hours every day of the year; 1 hour has a constant value/length, day or night, all through the year!"
