What is the main content of Xu Xiake's travel notes?

Xu Xiake's Travels (including Xu Xiake's Journey to the West) is the true record and crystallization of Xu Xiake's 30-year travel investigation. Its content is very extensive and rich, from the investigation of mountains, rivers and landforms to the exploration of strange peaks, caves, waterfalls and hot springs. From the ecological varieties of animals and plants to the description of handicraft industry, minerals, agriculture, transportation and urban construction; From local customs to ethnic relations and border defense, there are records. It provides extremely valuable information for the study of China's historical natural geography and historical human geography, and creates a precedent for China's geographical field investigation and systematic description of nature.

Xu Xiake's main contribution is to make a detailed investigation and record on the distribution, types, changes, characteristics and causes of peak forests, karst caves, karst gullies, stone buds, Liang Shi, circular depressions, sinkholes, natural bridges and geothermal phenomena in the vast limestone areas in southwest China, and to make a detailed record, analysis and research, which has a scientific explanation. It is the earliest precious document of karst landforms in China and even in the world, which has been opened up all over the world. In hydrology, he made a detailed investigation of the origins of many rivers and made a serious exploration of the sources and trends of various waters. He dared to break the traditional misconception and correct the shortcomings in previous studies and the mistakes recorded in local chronicles. In particular, his Textual Research on the Source of the Yangtze River correctly points out that the real source of the Yangtze River is Jinsha River, not Minjiang River, boldly denies Chen Xiangyin 1000' s erroneous assertion that "Min Mountain guides the river" for more than a thousand years, and also describes in detail the influence of climate and topography on plants. Xu Xiake's travel notes have made many scientific explanations for some peculiar natural geographical phenomena and revealed the inevitable natural laws.