Some of my story has already been told in Harper's and the National Geographic, to whose editors acknowledgments are due for permission to use the material in its present form. A glance at the Bibliography will show that more than fifty articles and monographs have been published as a result of the Peruvian Expeditions of Yale University and the National Geographic Society. Other reports are still in course of preparation. My own observations are based partly on a study of these monographs and the writings of former travelers, partly on the maps and notes made by my companions, and partly on a study of our Peruvian photographs, a collection now numbering over eleven thousand negatives. Another source of information was the opportunity of frequent conferences with my fellow explorers. One of the great advantages of large expeditions is the bringing to bear on the same problem of minds which have received widely different training. My companions on these journeys were, in 1909, Mr. Clarence L. Hay; in 1911, Dr. Isaiah Bowman, Professor Harry Ward Foote, Dr. William G. Erving, Messrs. Kai Hendriksen, H. L. Tucker, and Paul B. Lanius; in 1912, Professor Herbert E. Gregory, Dr. George F. Eaton, Dr. Luther T. Nelson, Messrs. Albert H. Bumstead, E. C. Erdis, Kenneth C. Heald, Robert Stephenson, Paul Bestor, Osgood Hardy, and Joseph Little; and in 1915, Dr. David E. Ford, Messrs. O. F. Cook, Edmund Heller, E. C. Erdis, E. L. Anderson, Clarence F. Maynard, J. J. Hasbrouck, Osgood Hardy, Geoffrey W. Morkill, and G. Bruce Gilbert. To these, my comrades in enterprises which were not always free from discomfort or danger, I desire to acknowledge most fully my great obligations. In the following pages they will sometimes recognize their handiwork; at other times they may wonder why it has been overlooked. Perhaps in another volume, which is already under way and in which I hope to cover more particularly Machu Picchu [1] and its vicinity, they will eventually find much of what cannot be told here. Sincere and grateful thanks are due also to Mr. Edward S. Harkness for offering generous assistance when aid was most difficult to secure; to Mr. Gilbert Grosvenor and the National Geographic Society for liberal and enthusiastic support; to President Taft of the United States and President Leguia of Peru for official help of a most important nature; to Messrs. W. R. Grace & Company and to Mr. William L. Morkill and Mr. L. S. Blaisdell, of the Peruvian Corporation, for cordial and untiring coöperation; to Don Cesare Lomellini, Don Pedro Duque, and their sons, and Mr. Frederic B. Johnson, of Yale University, for many practical kindnesses; to Mrs. Blanche Peberdy Tompkins and Miss Mary G. Reynolds for invaluable secretarial aid; and last, but by no means least, to Mrs. Alfred Mitchell for making possible the writing of this book. Hiram Bingham Yale University October 1, 1922 Contents