INTRODUCTION. 



11 



the summer of 1918 and the measurements and tabulation finished soon 

 after. I wish gratefully to acknowledge the courtesy of the editors of 

 the Astrophysical Journal and the Bulletin of the American Geograph- 

 ical Society for permission to use illustrations and extracts from articles 

 of mine which they have published. Plate 9 and figure 31 in the text 

 are from the former journal. Thanks are also extended to Professor 

 Ellsworth Huntington for the use of several text-figures which first 

 appeared in my chapter of his work (1914). 



TREES SUITABLE FOR CLIMATIC STUDY. 



During the course of this investigation the wood and growth of 

 numerous species of trees have been examined with reference to their 

 adaptability to the purposes herein described. The collections visited 

 include several in London, especially one in the South Kensington 

 Museum, fossils in the Jermyn Street Museum, the lumber-yards of 

 Messrs. W. W. Howard Bros. & Company, tree sections and fossils 

 in the geological museum at Berlin, fossils in the lignite beds of Grube 

 lisa near Dresden, and fossils chiefly in Munich and Vienna. In 



TABLE 1. List of trees in the Jessup collection whose rings were counted. 



