258 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 38 



RAMIFICATIONS OF GEOLOGY 



Geology is concerned with all agencies and phenomena that have 

 affected the earth in the past or are affecting it now. Some agencies, 

 such as the sun's energy, act upon the earth entirely from without. 

 Others act chiefly at the earth's surface. Among them are streams, 

 glaciers, winds, and waves. Still others, such as volcanism, earth- 

 quakes, and mountain-building agencies, act chiefly within the body 

 of the earth, though each of these may have strongly developed sur- 

 face manifestations. Gravity acts from without the earth as an 

 astronomical agency, but is also associated with every activity at the 

 earth's surface and within its mass. 



The geologist reads and interprets the geologic record in the rocks. 

 But this involves consideration of the agencies above mentioned and 

 through them the use of facts and techniques of other sciences, princi- 

 pally chemistry, physics, biology, and astronomy. A border zone lies 

 between geology and each of these sciences so that whether an in- 

 vestigation is geological may depend on its viewpoint or emphasis 

 rather than on the facts or techniques employed. 



The borderline sciences, geochemistry and geophysics, have devel- 

 oped to consider problems that fall between the adjacent fields in- 

 dicated by the names. 2 



Mineralogy may be cited as an example of the dependence of geol- 

 ogy on other sciences. Mineralogy has long been dependent on chem- 

 istry and optical physics for accurate determinations of mineral species. 

 More recently it has made use of the X-ray. Mineralogy applied 

 to rock study has developed into petrology; similarly applied to the 

 study of useful minerals it has developed into economic geology. 

 Both geochemistry and geophysics are extensively utilized in economic 

 geology, and geophysics has now become an important aid to the 

 petroleum geologist in his search for oil and gas. However, the view- 

 point of geology, the interpretation of the earth's history, is its own, 

 and geology's dependence on other sciences is probably no greater 

 than their dependence on it. 



Geology ramifies also into business, national, and private life. 



GEOLOGY AND THE MINERAL INDUSTRIES 



The mineral industries include, generally, those dependent on the 

 discovery and mining of mineral substances and their manufacture 

 into useful products. They give employment to many thousands of 

 our citizens. According to the Minerals Yearbook, 1937, published 

 by the Bureau of Mines, the mining industry by itself ranks last 

 among the four primary industries in the United States with respect 

 to capital invested, value of products, or number of workers employed. 



1 For a broader interpretation of geophysics, see Hubbert, M. K., The place of geophysics in a depart- 

 ment of geology, Amer. Inst. Min. and Met. Eng., Tech. Publ. 945, February meeting, 1938. 



