Thanks for valuable assistance are due and rendered to correspondents and to officers of the Bureau of Ethnology and of the United States Geological Survey, whose names are generally mentioned in connection with their several contributions. Acknowledgment is also made now and throughout the work to Dr. W. J. Hoffman, who has officially assisted in its preparation during several years, by researches in the field, in which his familiarity with Indians and his artistic skill have been of great value. Similar recognition is due to Mr. De Lancey W. Gill, in charge of the art department of the Bureau of Ethnology and the U. S. Geological Survey, and to Mr. Wells M. Sawyer, his assistant, specially detailed on the duty, for their work on the illustrations presented. While mentioning the illustrations, it may be noted that the omission to furnish the scale on which some of them are produced is not from neglect, but because it was impossible to ascertain the dimensions of the originals in the few cases where no scale or measurement is stated. This omission is most frequently noticeable in the illustrations of petroglyphs which have not been procured directly by the officers of the Bureau of Ethnology. The rule in that Bureau is to copy petroglyphs on the scale of one-sixteenth actual size. Most of the other classes of pictographs are presented without substantial reduction, and in those cases the scale is of little importance. It remains to give special notice to the reader regarding the mode adopted to designate the authors and works cited. A decision was formed that no footnotes should appear in the work. A difficulty in observing that rule arose from the fact that in the repeated citation of published works the text would be cumbered with many words and numbers to specify titles, pages and editions. The experiment was tried of printing in the text only the most abbreviated mention, generally by the author’s name alone, of the several works cited, and to present a list of them arranged in alphabetic order with cross references and catch titles. This list appears at the end of the work with further details and examples of its use. It is not a bibliography of the subject of picture-writing, nor even a list of authorities read and studied in the preparation of the work, but it is simply a special list, prepared for the convenience of readers, of the works and authors cited in the text, and gives the page and volume, when there is more than one volume in the edition, from which the quotation is taken. CHAPTER I. PETROGLYPHS.