295 years ago today, June 28, 1730 (May 14, 1730, the 1730 lunar calendar), the Jesuit missionary Bai Jin passed away. Bai Jin (Joachim Bouvet, 1656-1730), also known as Bai Jin, the word Mingyuan. Born on July 18, 1656 in Le Mans, France. He attended Jesuit school when he was young and received a comprehensive education in theology, linguistics, philosophy and natural sciences, with a strong interest in mathematics and physics. He came to China in the 26th year of Kangxi of the Qing Dynasty and was a person who made outstanding contributions to the cultural exchanges between China and the West in modern times. Bai Jin joined the Jesuits on October 9, 1678, and on July 23, 1687, he was one of the first six Jesuits to China for King Louis XIV. Before setting off, they were awarded the title of Fellows of the French Academy of Sciences and were charged with measuring the geographical location of various areas they passed and collecting scientific data. This group of missionaries, led by Father Hong Ruohan, crossed east from Brest, France, on March 3, 1685, passed through Siam (present-day Thailand), and arrived in Ningbo, Zhejiang in the summer of the 26th year of Kangxi of the Qing Dynasty (July 23, 1687), requesting permanent residence in China. One of the priests was detained by the King of Siam, and no one came outside China. The remaining five finally arrived in Beijing on February 7, 1688. These five people are Hong Ruohan, Li Ming, Bai Jin, Zhang Cheng, and Liu Ying. Jin Hong, the governor of Zhejiang at that time, thought that these people had entered the country without passports, and the Ministry of State Affairs and Rites planned to send them back to China. Because Nan Huairen, the Belgian priest who was serving as the Imperial Astronomical Supervisor at that time, was old, Kangxi was looking for new people to replace him, so he allowed them to enter Beijing. Two priests, Bai Jin and Zhang Cheng, were immediately left to serve in Beijing by Emperor Kangxi, while the other three were allowed to travel to various provinces to freely spread the gospel. In 1688, Zhang Cheng and others entered the palace and presented advanced European astronomical instruments at that time, including a quadrant with altimetry telescope, a level, an astronomical clock, and some mathematical instruments. Kangxi liked it very much and ordered it to be placed in the royal room in the palace, and ordered Bai Jin and Zhang Cheng to learn Manchu and learn it nine months later. While Bai Jin and Zhang Cheng explained to Kangxi the use of the instruments they introduced, they also explained some astronomical phenomena to him, and introduced the new methods of observing solar and lunar eclipses by the French Italian astronomer Jean Dominique Cassini (1625 - 1712) and the French mathematician and astronomer Philippe Lahiere (1640 - 1718), and drew pictures to illustrate them. Bai Jin also forwarded to Emperor Kangxi the altimetry telescope given to him by Duke Main, son of King Louis XIV. In 1690, Zhang Cheng, Bai Jin and others systematically taught geometry and arithmetic to Kangxi. Zhang Cheng and Bai Jin compiled an outline of practical geometry in Manchu; later, Bai Jin and Zhang Cheng's Manchu speeches were compiled into a volume and translated into Chinese, and Kangxi personally reviewed and prepared a preface. This is the Manchu version of the "Geometry Original" currently stored in the Palace Museum, while the Chinese version includes "Mathematical Essence". In 1691, at the request of Emperor Kangxi, Bai Jin and Zhang Cheng prepared to talk about the history of European philosophy, but they could not proceed as planned because Kangxi was ill and could not work hard. They saw that the emperor wanted to understand human tissues and their functional drivers, as well as the principles of the beneficial effects that occur in these tissues, so they decided to teach human anatomy. On July 4, 1693 (the thirty-second year of Kangxi), the quinine donated by Bai Jin and Zhang Cheng cured Emperor Kangxi of malaria. In order to reward them for their contributions, Emperor Kangxi ordered that land be given to build a house within the Xi'an Gate of the Imperial City., as a residence for missionaries. At the same time, in order to attract more French Jesuits, Emperor Kangxi appointed Bai Jin as a special envoy to France, carrying 49 volumes of precious books presented to the French king, and returning to China to recruit more missionaries to China. Bai Jin traveled between land and land, arriving in Brest in March 1697, and returned to Paris in May. At that time, there were only 23 volumes of Chinese books in France, so the set of Chinese books brought back by Bai Jin made Louis XIV very happy and surprised. In that year, Bai Jin published two books,"The Current Situation of China" and "Emperor Kangxi," which were dedicated to the Duchess of Burgundy and Louis XIV respectively. Bai Jin portrayed Emperor Kangxi as another Sun King in order to win Louis XIV's favor with Kangxi and gain further financial and human support for the mission area, namely, sending more Jesuits to China and paying annual salaries. Louis XIV generously agreed to this request and authorized Bai Jin to spend 10,000 francs to prepare gifts for Emperor Kangxi. After everything was ready, in March 1698, the "Amfitlit" loaded a group of nine Jesuits from La Rochelle and headed for Guangzhou. In addition to Bai Jin, the other eight were Jean-Baptiste Regis, Jean-Charles Etienne de Broissia, Charles Dolze, Louis Pernon, Joseph Hennry Premare, Dominique Parrenin, Philibert Geneix, and Charles de Belleville. Prior to this, Bai Jin had arranged for several other Jesuits to leave first. Jean Francois Foucquet and Gabriel Barborier left Brest on the "La Zeine" in January 1698, and replaced the "La Bon" in Port Louis to join the other three Jesuits already on board. In addition, when they were in India, two French members came to China together. As a result, Bai Jin brought back a total of 15 Jesuits during his trip, many of whom made outstanding contributions to Sinology. They returned to Beijing in 1699 and brought with them a batch of precious carvings donated by the King of France. Bai Jin's great success in this mission was deeply praised by Emperor Kangxi. The emperor appointed him as the tutor of the Crown Prince. Bai Jin and Emperor Kangxi shared the same view. They hoped to find common ground between Confucianism and Catholicism so that China could accept and convert to Catholicism. It is said that Emperor Kangxi himself once declared that he would believe in Catholicism and caused the entire people of China to convert to this religion. Missionaries in China all went all out to realize this ideal, but in the end they failed. At that time, Bai Jin tried his best to find traces of Catholic legends in the "Four Books and Five Classics." Through research, he believed that he had discovered records of the first spread of Catholic religion in China classical books, so he and two colleagues wrote the book "Respect for Heaven in Ancient and Modern Times". In 1705, Dora, the Pope's special envoy, came to China to issue a ban on Pope's "etiquette." Emperor Kangxi was furious and ordered him to be expelled from Beijing. But the emperor believed that the Pope's wrong decision was due to his ignorance of China and his belief in the slander of bad people. So he planned to send Bai Jin to Rome to explain to the Pope. Later, due to serious differences of opinion with Duo Luo, Kangxi ordered Bai Jin to be recalled, but he failed to make the trip. After Emperor Kangxi came into contact with Western missionaries, he became interested in earth measurement while learning to use astronomy and mathematical instruments. However, Kangxi's idea of surveying and mapping the whole country first sprouted when the rebellion of the Three Kingdoms was put down. Maps played an important role in the war, but also exposed many flaws. Some maps are rough and fuzzy, and some are even full of errors. According to Zhang Cheng's Diary, after the signing of the Treaty of Nibchu between China and Russia, on January 26, 1690, Kangxi asked Zhang Cheng to introduce the route of the Russian mission to China. Zhang Cheng told him the story according to a map drawn by the West. He found that the part about China in the map, especially the northeastern part of China, was too simple and crude, so he decided to rely on missionaries to draw a national map using Western measurement technology. At the end of 1708 (47th year of Kangxi), Bai Jin was ordered to lead a team with Lei Xiaosi (1663 - 1738), Du Demei (1668 - 1720) and others to survey the Great Wall, measuring the gates, fortresses and nearby cities, river valleys, and water currents. In January 1709, they returned to Beijing and brought back a map about 15 feet long. After that, Fei Yin and others joined. This time, Bai Jin and others led a team to survey and map the west of the Great Wall, that is, Shanxi, Shaanxi, Gansu and other provinces, to Hami, Xinjiang. The rest of the missionaries were also sent to various provinces to survey and draw the "Imperial Yu Complete Map". Bai Jin and others also participated in the final summary work, which took nine years to be finally completed. After being approved by Kangxi, the "Complete Overview of the Imperial Yu" and the provincial sub-maps were drawn in 1718. This is the first time in the world that a geodetic survey has been completed on such a vast land. In this measurement, the unit of length was unified and the longitude length was found to be different from top to bottom, confirming that the earth is oblate. Bai Jin died in Beijing on June 28, 1730 (the eighth year of Yongzheng) at the age of 74. The body was later buried in the Zhengfu Temple Cemetery. The deeds of his life fully prove his firm belief and sincere missionary spirit, as well as the political talents common among Jesuits. As far as his personal character is concerned, he is a gentle, honest, loyal and reliable person. Even if he is sometimes dissatisfied with others, he will never slander others; he is kind to others, so he can always get along well with people around him, and thus he can always realize his wishes and requirements well.