This is a collection of handwritten manuscripts by Sin Gyeong-jun (1712~1781/pen-name: Yeoam) posthumously published in typed letters in 1910. Sin Gyeong-jun, a geographer during the late Joseon Period (1392-1910), was the first person to use the term “Baekdu Daegan” to refer to the mountain range that extends from Baekdusan Mountain to Jirisan Mountain and forms the backbone of the Korean Peninsula. Regarding the system of mountain ranges on the Korean Peninsula, he said that Baekdu Daegan forms the backbone of the Korean Peninsula, with one leading range and thirteen leading veins existing as its ancillary system. This idea had a great impact on the creation of Daedong yeojido (Map of the Great East) by Kim Jeong-ho in 1861.