Chapter 10 Section 3 Timing Instruments

The sun rises every morning and sets in the evening, and the shadow of the surface moves from west to east. The position of the shadow can tell the time, which is self-evident.With the advancement of production and the acceleration of the pace of life, people demand to know more accurate time, so the watch has evolved into a sundial.A sundial consists of a sundial needle and a stone sundial surface with the sundial needle as the center. The sundial surface is engraved with radial bearing lines, and the time can be known according to the coincidence of the needle shadow and the bearing lines.

In the initial stage of the transition from a watch to a sundial, the surface of the sundial is generally placed horizontally, which is called a horizontal sundial.The horizontal longitude of the sun changes unevenly, which means that the azimuth scale on the horizon sundial will not be equally divided if it is equal, and will not be equal if it is equally divided.From the perspective of use, it is neither convenient nor accurate.Equatorial sundials have distinct advantages over horizon dials.Since the face of the sundial is parallel to the celestial equator, the equal time scales must equally divide the circumference.There are scales on both sides of the sundial, the south side is used after the vernal equinox, and the north side is used after the autumn equinox.

Leak is an instrument that uses the amount of water to measure time.Leak, refers to clepsydra, engraved, refers to engraved arrows.Leu Ke is an all-weather instrument that can make up for the limitations of sundials and is an important timer in ancient China. Abundant historical materials tell us about the main process of the development of leak engraving.Leak Ke was originally just a pot with a small hole in the bottom, and people roughly estimated the time by the remaining water in the pot.Later, with the help of an arrow engraved with scales, stand in the water, and calculate the time by the height of the arrow shaft when the water surface is submerged.Due to the surface tension of the water, an upward attachment surface is formed around the arrow shaft, which makes the reading inconvenient, so the flooded arrow leak gives way to the sinking arrow leak soon after.The arrow tail of the sinking arrow must have a buoyant object, such as bamboo or wood, so that the arrow floats on the water, and the arrow passes through the lid of the pot.When the arrow shaft descends with the loss of water, the scale aligned with the plane of the pot lid is the time at that time.Obviously, the scale order of Sunken Arrow and Drowned Arrow should be reversed.

According to the principle of fluid mechanics, the speed of water flow is related to the height of the water surface. Simply relying on a clepsydra for timing will inevitably affect the stability of timing.If you keep adding water so that the water level of the clepsydra does not drop, then use a container to collect the water flowing out evenly from the clepsydra, put the floating arrow in the container, and observe the height of the arrow floating to know the time. This is the floating arrow leak.However, there is always an interval between artificial water addition, and the water surface height still inevitably changes before and after adding water.The ancients realized this, and the solution was very unique: use another clepsydra to replenish the water, and in order to make this pot replenish water evenly, add a third pot.So the second-level clepsydra appeared in the Eastern Han Dynasty, the third-level clepsydra appeared in the Jin Dynasty, and the fourth-level clepsydra appeared in the Tang Dynasty.A thirsty horse is a siphon.Use thirsty horses to draw water, suitable for any container.A special clepsydra is no longer necessary, but the chronometers with thirsty horses still use the name "clepsydra".

To keep the water level of the clepsydra constant, multistage clepsydra is not the only way.Yan Su in the Song Dynasty took a different approach and designed a clepsydra with a water outlet, called the lotus leaker.The lotus clepsydra only has two stages of clepsydra, and there is a water diversion pipe on the side of the lower clepsydra. As long as the amount of water injected into the lower clepsydra by the upper clepsydra exceeds the amount of water discharged by the lower clepsydra, the water beyond the water diversion opening must be diverted, and the lower clepsydra can be maintained. The water surface is stable.

Since the water transport is controlled by the flowing water of the clepsydra, of course it can also reflect the time, and the water transport observatory includes the time telling system.In fact, the timekeeping system can be completely independent and does not need to be linked with other instruments. Guo Shoujing designed and manufactured a hydraulic timer called the Daming Hall Lamp Leaker. Among the folks, the most commonly used timing tool is more fragrant.Uniform ones are more fragrant, and their length is proportional to the burning time.Due to air flow and humidity changes, the precision of more fragrant will not be too high, but it can meet the needs of people's lives.

A timing tool called a roll (gun roll) bullet is commonly used in the army.The principle is roughly as follows: copper balls of the same weight roll down the bamboo tube from the same height, and the required time is the same. Several copper balls roll down alternately, counting the number of times.Roller ammunition is small in size, easy to carry, and not affected by the weather, especially suitable for marching and fighting. It is now known that since the Western Han Dynasty, the system of 12 hours a day has been implemented.Each hour has a name, that is, the twelve earthly branches of Zi, Chou, Yin, Mao, Chen, Si, Wu, Wei, Shen, You, Xu, and Hai.The essence of time is period rather than time. For example, Zi time is equivalent to two hours between 23:00 and 1:00, ugly time is equivalent to 1:00 to 3:00, Yin time is equivalent to 3:00 to 5 :00, and so on.After the Southern and Northern Dynasties, each hour was subdivided into two parts: the beginning and the beginning. For example, the beginning of the hour refers to an hour between 23:00 and 0:00, and the hour of the hour is from 0:00 to 1:00. The portable equatorial sundial is based on Chuzheng is divided into 24 time periods, which coincides with the current time system, and the name "hour" comes from this.