How did the ancients use tortoise shells for divination?

Because I know a little about divination, I have studied Zhouyi, astrology and palm reading. Let me briefly talk about the principle of tortoise shell divination: take appropriate tortoise shell with clear lines, wash it and offer it, as for the altar fire. Taoist priests chanted scriptures, danced staves and resorted to some long-lost ceremony. After a period of time, there will be cracks in the tortoise shell.

Because the cracks are random and the lines of tortoise shells are similar, we can answer the question by judging the tortoise shell area where the cracks pass. Generally speaking, it is a bit like a cryptographic system, and the interpretation rules are similar to key mapping plaintext. It's just that the rules are complicated and changeable, so it's hard to say.

Oracle Bone Inscriptions and Jia Bu in Shang Dynasty. Human sacrifice and human sacrifice, which prevailed in the Yin and Shang Dynasties, were always associated with the worship of God. The main reason is that the establishment of the slave kingdom in the Yin and Shang Dynasties needed a supreme god to maintain its religious rule, and all phenomena were described as the will of this great god. Therefore, the gods and ancestors of Yin people have supreme authority, which is the social root of Yin people's worship of gods.

Divination is a method of judging good or bad luck by symbols, which was very popular in Yin and Shang Dynasties. Slave owners made full use of this religious technique and reached the level of asking for everything. When merchants used bone divination, turtle divination also appeared. Therefore, Oracle Bone Inscriptions and Jia Bu are one of the most precious historical and religious relics left over from Shang Dynasty. Oracle Bone Inscriptions is a written note related to divination after the ancients used Oracle Bone Inscriptions to divine good or bad luck. It can be seen from the archaeological excavation of Shang ruins that Oracle Bone Inscriptions was mainly used in the early Shang Dynasty, and the shoulder blade of cattle was the most used material by Oracle Bone Inscriptions in Yin Dynasty. In addition, there are sheep bones, pig bones, deer bones and a small amount of tortoise shells. After the middle and late period, Jia Bu coexisted with Oracle bones, and sometimes Jia Bu even surpassed Oracle bones.