Feng Shui experts divide the terrain of China's mountains into three parts, namely, the northern dry dragon, the middle dry dragon and the southern dry dragon, with the South China Sea, the Yangtze River, the Yellow River and the Yalu River as the boundaries. Xu Shanji's "What the Son of Man Should Know: The Dragon Law": "There are three major waters in the world; Yellow River, Yangtze River and Yalu River. The Yangtze River and the South China Sea are in the East China Sea, the Yellow River and the Yangtze River are in the East China Sea, and the Yellow River and the Yalu River are in the Three Seas. " Three dry dragons all originated from Kunlun. Helan, surrounded by Yinshan Mountain in the north, enters the Three Seas through Youyan, with branches of Hengshan Mountain, Taihang Mountain and Yanshan Mountain, ending in Yanjing. Miao Xiyong's "Burying Wings" says: "Yan Dou, the northern dragon is exhausted, the duck is green and the world is behind, and the Yellow River holds the front, welcoming the factions, helping the recovery, and the northern meeting." Zhonglong entered Shu Han and Guan, dispersed into Zhongnan, Taihua and Taiyue Mountain, and carried water into the sea. Luoyang is between heaven and earth, the quenching of the Central Plains. Nanlong goes to Yunnan and Donglong goes to Yuanling. Its branches are Xiangjiang Wuling, Jiuben Hengshan, Kuanglu Gengyin, Tianmu Xianxia and Cangtiantai Siming. Jinling always has its situation. Feng shui experts believe that if you want to weave a real dragon, you must first understand the general trend. Look at the water source on the map, check the mountains, know how to peel and change, and distinguish the branches, so as to find the cave of the real dragon.