Chapter 38 Section Three

Whether it is the 16-hour system or the 12-hour system, it is judged according to the position of the sun or the appearance and disappearance of the situation, but it is not easy for ordinary people to judge accurately, and it is too rough to use, so people invented it again. Missing engraving, used to record time. "Zhou Li" contains the Qihu family, and "Hanshu" contains the rate of the order, both of which are officials in charge of leaked carvings. It can be seen that as late as the Zhou Dynasty, officials used leaked carvings to record time. According to records, pre-Qin omissions were mainly used for military purposes.It was not applied to astronomy until the calendar was changed in the early Han Dynasty.After being applied in astronomy, its precision and the method of use have been greatly improved.In the pre-Qin period, it is worth further research whether it has started to measure and tell the time continuously with the omissions.As a continuous time measurement and time reporting system, and put into normal use, it began about after the beginning of the Western Han Dynasty.

The method of use at the beginning is roughly like this: divide a day and night into 100 ticks, summer solstice with 60 ticks during the day, and night with 40 ticks; winter solstice with 40 ticks during the day and 60 ticks at night;However, astronomers also count the two and a half quarters before and after the sun enters and exits as the daytime. In this way, the summer solstice has 65 quarters during the day and 35 quarters during the night; the winter solstice has 45 quarters during the day and 55 quarters at night;Day and night are used separately, and when day begins, the clepsydra is filled with water on which a graduated arrow floats.As the pot of water leaks down, the floating arrow gradually sinks, and the ticks on the arrow at each moment are read from the mouth of the pot to tell the time.Usually, the number of engravings of an arrow is marked in the middle, and the upper and lower parts are divided into two. Therefore, when telling the time, it is called day leaking water × engraving, or day leaking water × engraving; night leaking Shangshui × engraving, night leak not Do × engraved.When day and night alternate, no matter whether the pot of water is leaking or not, it should be refilled with water and start leaking again.

Since the number of ticks of day and night varies in different seasons, it would be inconvenient and inaccurate to use arrows with the same scale.So the ancients invented the method of using different arrows in different seasons.In the Western Han Dynasty, 40 arrows were used a year, and one arrow was changed every nine days.In the process of using it, I found that the method of changing arrows according to the number of days is not scientific, because the change of day and night near the winter solstice and summer solstice is not significant, but the change is very significant near the vernal equinox and autumnal equinox. Therefore, in the early Eastern Han Dynasty, the north-south direction of the sun was changed. An arrow is replaced every two degrees and four minutes, and 40 arrows are still used.The Eastern Han Dynasty and Emperor Shi made a small improvement, stipulating that the sun should be replaced by one arrow every two degrees of north-south movement, and 48 arrows should be used throughout the year.