The field investigation therefore occupied twenty-two months, involving nearly 32,000 miles of travel and more or less time spent with about twenty tribes. To obtain exact knowledge of the ceremony, the author took part in the dance among the Arapaho and Cheyenne. He also carried a kodak and a tripod camera, with which he made photographs of the dance and the trance both without and within the circle. Several months were spent in consulting manuscript documents and printed sources of information in the departments and libraries at Washington, and correspondence was carried on with persons in various parts of the country who might be able to give additional facts. From the beginning every effort was made to get a correct statement of the subject. Beyond this, the work must speak for itself. As the Ghost dance doctrine is only the latest of a series of Indian religious revivals, and as the idea on which it is founded is a hope common to all humanity, considerable space has been given to a discussion of the primitive messiah belief and of the teachings of the various Indian prophets who have preceded Wovoka, together with brief sketches of several Indian wars belonging to the same periods. In the songs the effort has been to give the spirit and exact rendering, without going into analytic details. The main purpose of the work is not linguistic, and as nearly every tribe concerned speaks a different language from all the others, any close linguistic study must be left to the philologist who can afford to devote a year or more to an individual tribe. The only one of these tribes of which the author claims intimate knowledge is the Kiowa.