48 THE U. S. GEOLOGICAL SURVEY 



problems of geology?" feeling assured that ultimately all 

 such research will be of economic value. 



In the first decade of the Survey's existence its geologic 

 work was largely devoted to the investigation of the broad 

 problems of American geology, and the formulation of a 

 fundamental geologic classification as the scientific basis for 

 the preparation of the geologic map of the United States. As 

 the major features of this basic problem approached solution, 

 the Survey's attention was increasingly turned to the geologic- 

 al survey of the country. Researches in geologic history and 

 theory have nevertheless been steadily prosecuted. Thus, for 

 some time past the Survey has been engaged in a study of the 

 work of glaciers, the geologic history of the continent during 

 the Quaternary period, and the classification and correlation 

 of the sedimentary rocks of the entire country, work involv- 

 ing the study of all North American fossil faunas and floras 

 and their comparison with those of other parts of the world. 



Broad geologic research may involve correlative research in 

 physics and chemistry. Among the researches of this type 

 carried on by the Survey are those relating to questions of 

 terrestrial physics, such as the mechanics of the Panama Canal 

 slides, the variation in the water content of rocks from Pan- 

 ama, the increase of earth temperatures with increase of depth, 

 and the electric activity of ore deposits. 



In addition to chemical and physical researches directly re- 

 lated to geologic researches, the Survey from time to time 

 has made researches which may be said to be directed to the 

 elucidation of general physical and chemical problems that 

 have no exclusive relation to the development of geologic 

 theory. Thus, work has been done by the Survey in a revi- 

 sion of the fundamental atomic weights, on the radio-activity 

 of ores, and on the geochemical interpretation of water anal- 

 yses. Much of the work now done by the Carnegie Geo- 

 physical Laboratory was begun in the Geological Survey. 



