NOTE TO THE READER. 



This volume as a whole deals with climate, but various parts are concerned with 

 particular aspects of the problem. The reader who is interested in one special phase is 

 referred to the following chapters: 



Physical aspects of the Southwest, Chapters I to VI. 



The Ancient People of the Southwest, Chapters VII to X. 



The Measurement of Rainfall by the Growth of Trees, Chapters XI to XIV. 



The Maya Civilization and Changes of Climate in the Torrid Zone, Chapters XV to XVIII. 



Theories of Climatic Changes, Chapters XIX and XX. 



The Climate of the Geological Past, Chapter XXI. 



The volume may be divided in another way according to the sciences with which the 

 different chapters are more especially concerned. In this division, however, it must be 

 recognized that there is much overlapping, for the same chapter often deals with several 

 sciences. 



Climatology, Chapters I, XIV, XVI, XIX. 



Geology, Chapters II, IV, V, VI, X, XX, XXI. 



Botany, Chapters III, XI, XII, XIII, XIV. 



Archeology, Chapters VI, VII, VIII, IX, X, XVI, XVII, XVIII. 



Ethnology, Chapters VII, XV, XVII, XVIII. 



The reader who desires to understand the main outline of the theories here presented, 

 but does not care to go through all the details of evidence is advised to read the Introduc- 

 tion, and Chapters VI, VII, IX, XIII, XIV, XVI, XVII, XIX, and XX. 



vi 



