When in 1850 appeared the Report of the Secretary of War for the United States, containing Mr. J. H. Simpson's account of the Cliff Dwellings in Colorado, great surprise was awakened in America, and since then these remains have been investigated by many explorers, of whom I need only name Holmes' "Report of the Ancient Ruins in South-West Colorado during the Summers of 1875 and 1876," and Jackson's "Ruins of South- West Colorado in 1875 and 1877." Powell, Newberry, &c., have also described them. A summary is in "Prehistoric America," by the Marquis de Nadaillac, 1885, and the latest contribution to the subject are articles in Scribner's Magazine by E. S. Curtis, 1906 and 1909.