Introduction to long stone slips: Before the invention of paper, the Han people used bamboo slips to record history, while the Tujia people carved words on flat stones to form stone slips. The layers of thin rock in front of them may be the documents of the Ba people. Shiku. In fact, this is the masterpiece of the sea 200 million years ago. At that time, there was a vast ocean and the result of the precipitation of calcium substances in the water. Marine fossils can be found in it.