William Edgar Geil, a member of the Royal Geographical Society and an explorer from Britain, made multiple visits to China to study the Great Wall. He wrote several works, including The Great Wall of China. In 1908, he organized an expedition and hiked the main line of the Great Wall, taking nearly three months to travel from Shanhaiguan Pass to Jiayuguan Pass. His writings provided a detailed account of the origin, current state, function, and significance of the Great Wall, accompanied by many exquisite photographs. Geil believed that the Great Wall was not only a symbol of peace but also a defensive line against foreign aggression. His awe and admiration for the Great Wall can be seen in his repeated use of the phrase "remarkable" to describe it.