Introduction to the Dayon Drilling Period: In the Northern Song Dynasty, people from Zhuotongjing Town, Daying County, Sichuan invented the brine mining technology in Zhuotongjing. The local chronicles recorded the specific drilling method: "Select a salty source and drill it with an iron cone. The well is as big as a bowl. Four or five large bamboo poles are used to connect it to make it long. Iron cones are tied with bamboo branches and dug into the bamboo. There are four iron claws at the bottom of the well. It will stop after sixty or seventy days or more than a hundred feet of salt water. "