Timothy H. O'Sullivan, 1871-1874 (survey), 1873 (expedition), 22. Circle Wall, Canon de Chelle. Here the Canon bends from an easterly direction, nearly due north, the walls maintaining a perpendicular height of about 1,200 feet., [Wheeler Survey, Explorations and Surveys West of the 100th Meridian], Stereocard, detail, Etherton Gallery, LL/24751
Timothy H. O'Sullivan 1871-1874 (survey), 1873 (expedition) 22. Circle Wall, Canon de Chelle. Here the Canon bends from an easterly direction, nearly due north, the walls maintaining a perpendicular height of about 1,200 feet. [Wheeler Survey, Explorations and Surveys West of the 100th Meridian]
