6 CLIMATIC CYCLES AND TREE-GROWTH 



contact. The rings in the beams of ancient ruins tell a story of the 

 time of building, both as to its climate and the number of years 

 involved and the order of building, perhaps ultimately the date of 

 building. All this is anthropology, and much data from the archae- 

 ologists will help in identifying the rings in beams and supply valuable 

 climatic records of long-past times. 



ACKNOWLEDGMENTS 



The author's acknowledgments with thanks are most cordially 

 tendered to many sources of help. First of all, to the Carnegie Institu- 

 tion of Washington for bearing the expenses of publication and for 

 the yearly appropriations through its Division of Ecological Research, 

 to aid this study by securing suitable help and occasional field trips and 

 instruments ; and equally to the University of Arizona for so reducing the 

 author's teaching hours as to permit this investigation; to Mr. Clarence 

 G. White, of Redlands, California, for the White Research Fund, 

 which permitted the building of the periodograph in its latest and 

 most effective form; to Major L. F. Brady, whose interest in the 

 Flagstaff "buried trees," in prehistoric beams, and in the "burnt 

 trees" has brought in valuable material; to Dr. F. N. Guild, who 

 identified and described the white crystals found in buried trees and 

 named the mineral "fiagstaffite"; to Vilhjalmar Stefansson and the 

 Canadian Geological Survey for specimens from the American Arctic; 

 to Dr. W. P. Wilson and the Commercial Museum in Philadelphia for 

 access to the fine sections of Brazilian pines; to Mr. Percy J. Brown 

 and nephew, of Scotia, for their hospitality and cordial help in collect- 

 ing coast redwoods; to Mr. R. E. Burton for help with the Santa 

 Cruz redwoods; to Dr. E. S. Miller, of Flagstaff, Arizona, for help 

 with "buried trees "and in collecting the group called "Flagstaff 

 Northeast"; to the Whitesides, at Calaveras Grove, California, for 

 opportunity to compare the growth records there with those at the 

 southern sequoia groves; to Col. W. B. Greeley, of the U. S. Forest 

 Service, and Mr. Stephen Mathers and Mr. Arno Commerer, of the 

 National Park Service, for letters of permission to secure material 

 in such places; to the many officials of the U. S. Forest Service who 

 have helped me, especially Mr. G. A. Pearson, of Flagstaff, through 

 whose efforts the 640-year yellow pine was found and who has secured 

 many borings for me; to Mr. T. A. Riordan and Mr. M. J. Riordan 

 for the largest yellow pine section yet obtained in northern Arizona, 

 and many other kindly bits of assistance; to the National Geographic 

 Society and Mr. Neil M. Judd, director of its field work at Chaco 

 Canyon, and to Dr. J. A. Jeancon, of Denver, and Dr. A. V. Kidder, 

 of Andover, Massachusetts, also to Dr. Clark Wissler, of the American 

 Museum, and Mr. Earl H. Morris, for the trip to Aztec and entertain- 

 ment at Chaco Canyon and extensive contributions to the large 



