Dr John DUDGEON (1837-1901) was a Scottish “medical missionary, an accomplished Chinese scholar and an enthusiastic amateur photographer who spent … some thirty-eight years in Peking.” Dudgeon wrote an important treatise on Photography (a how to manual) in Chinese, Tuoying qiguan (1873).  He was on friendly terms with fellow photographers Thomas Child and John Thomson.  Source: Terry Bennett History of Photography in China - Western Photographers - 1861-1879, Quaritch 2010, pp37-55.