Letter by Bak Gyu-su

This letter was written by Bak Gyu-su (1807-1877) in 1849, while he was serving as the administrative head of Yonggang-hyeon, to his elder brother to ask him how he was doing. The letter expresses his concerns about people's feelings of uneasiness at the news that Qing envoys had crossed the border, and mentions the locations of Yonggang and Seoul, revealing his awareness of scientific knowledge newly introduced from the West. He wrote, for instance, that Yonggang is located at 39°N latitude, two degrees higher than Seoul, thus accounting for the difference in the duration of summer and winter between the two cities. He also compared the longitudes of the two Korean cities with that of the Qing capital, Yanjing (present-day Beijing).