长城是我国古代一项伟大的建筑奇迹,其在漫长的历史时期发挥着巨大的国防功能。同时,它也是中华文化圈内农耕与游牧这两大部类文明形态的分界线。华裔历史学家黄仁宇先生在他的《中国大历史》中论述农业与游牧业关系时,曾有长城是建在“15英寸等雨线”上的观点,就是说,由于中国特有的地域生态才造就了万里长城。那么,长城与15英寸等雨线之间究竟存在什么样的关系?其中又蕴含着什么样的地理历史元素 The Great Wall is a great architectural miracle in ancient China, which played a huge national defense function in the long historical period. At the same time, it is also the dividing line between the two major civilizations of farming and nomad in the Chinese cultural circle. When Mr. Huang Renyu, a Chinese-American historian, discussed the relationship between agriculture and pastoralism in his “Great History of China,” there was a view that the Great Wall was built on the “15-inch rain line.” In other words, due to the unique geographical features of China Ecology has created a Great Wall. So what is the relationship between the Great Wall and the 15-inch rain line? What kind of geographical and historical elements