Col. Mallery’s studies in pictography commenced in the field. He was stationed with his military command at Fort Rice, on the upper Missouri river, in the autumn of 1876, and obtained a copy of the remarkable pictograph which he then called “A Calendar of the Dakota Nation,” and published under that title, with interpretation and explanation, in Vol. III, No. 1, of the series of bulletins of the U. S. Geological and Geographical Survey of the Territories, issued April 9, 1877. This work attracted attention, and at the request of the Secretary of the Interior he was ordered by the Secretary of War, on June 13, 1877, to report for duty, in connection with the ethnology of the North American Indians, to the present Director of this Bureau, then in charge of the Geographical and Geological Survey of the Rocky Mountain Region. Upon the organization of the Bureau of Ethnology, in 1879, Col. Mallery was appointed ethnologist, and has continued in that duty without intermission, supplementing field explorations by study of all accessible anthropologic literature and by extensive correspondence. His attention has been steadily directed to pictography and to sign-language, which branches of study are so closely connected that neither can be successfully pursued to the exclusion of the other, but his researches have by no means been confined to those related subjects. The plan and scope of the present work may be very briefly stated as follows: After some introductory definitions and explanations general remarks are submitted upon the grand division of petroglyphs or pictures upon rocks as distinct from other exhibitions of pictography. This division is less susceptible of interpretation than others, but it claims special interest and attention because the locality of production is fixed, and also because the antiquity of workmanship may often be determined with more certainty than can that of pictures on less enduring and readily transportable objects. Descriptions, with illustrations, are presented of petroglyphs in North America, including those in several provinces of Canada, in many of the states and territories of the United States, in Mexico, and in the West Indies. A large number from Central and South America also appear, followed by examples from Australia, Oceanica, Europe, Africa, and Asia, inserted chiefly for comparison with the picture-writings in America, to which the work is specially devoted, and therefore styled extra-limital petroglyphs. The curious forms called cup sculptures are next discussed, followed by a chapter on pictographs considered generally, which condenses the results of much thought. The substances, apart from rocks, on which picture-writing is found are next considered, and afterwards the instruments and materials by which they are made. The subjects of pictography and the practices which elucidate it are classified under several headings, viz: _Mnemonic_, subdivided