a nineteenth-century explorer that first led me into the relatively
unknown region between the Apurimac and the Urubamba, sometimes called
"the Cradle of the Incas." Although my photographs cannot compete with
the imaginative pencil of such an artist, nevertheless, I hope that
some of them may lead future travelers to penetrate still farther
into the Land of the Incas and engage in the fascinating game of
identifying elusive places mentioned in the chronicles.

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,