46 THE U. S. GEOLOGICAL SURVEY 



The principles controlling mineral deposition and the laws 

 governing the occurrence of ore bodies can be satisfactorily 

 determined only as a result of the comprehensive study of 

 many mines and mining camps. This work is beyond the 

 reach of individuals but is appropriate to the national or- 

 ganization. The application of the principles to particular 

 ore bodies and camps is quite within reach of the individual 

 mining engineers charged with development work. 5 



In large measure geologic and mineralogic data that form 

 a basis for researches of this type already exist in the results 

 of the Survey's work. The search made for specific mineral 

 deposits by the Survey also frequently contributes materials 

 of considerable theoretic value. 



The broad and searching observations which should accom- 

 pany every piece of good economic work comprehend data 

 that are eventually combined in the construction of new 

 scientific hypotheses, some of which, as more observations 

 accumulate, grow into established laws or principles that are 

 in turn of the greatest practical consequence. Thus the de- 

 tailed studies of the metalliferous deposits in one region or 

 another bring to light evidence from which to determine the 

 genesis of the ores and the modes or conditions of their oc- 

 currence. 6 



Both these classes of existing data must, however, frequently 

 be supplemented by special studies in the field and in the 

 Survey's laboratories. As illustrative of the Survey's chem- 

 ical and physical researches may be mentioned extensive 

 laboratory investigations of the diffusion of gold and silver 

 into lead and tin, the linear force of growing crystals, the 

 migration of natural oil in certain sands, and the enrichment 

 of ores of silver, copper, etc. 



The Survey's investigations of certain problems of mineral 

 occurrence border closely upon investigations made by the 

 Bureau of Mines in the field of mineral utilization. The Sur- 



6 The United States Geological Survey : Its Origin, Development, 

 Organization and Operations, 1904. Bulletin No. 227, p. 31 f. 

 6 Report of the Director, 1912, p. 16. 



