GEOLOGY IN EVERYDAY LIFE MANSFIELD 261 



not only by pointing out more favorable areas but also by preventing 

 search in unfavorable areas. 



Fuels — coal. — Geologists in Federal and State surveys, as well as 

 those in private employ, have labored many years to make known the 

 nature and extent of the nation's coal resources. We now know in 

 greater or less detail where the deposits of coal of different ranks, from 

 lignite to anthracite, lie, how extensive they are, how rich in heating 

 value, and which beds among them are best adapted for such purposes 

 as coking and steam production. Some years ago the Geological 

 Survey published a map showing the nature and distribution of the 

 coal fields of the United States, which has proved a very useful sum- 

 mary. Although the number of publications emanating from these 

 sources is large, the work is far from complete because of the wide 

 distribution of the deposits and the refinements of study needed in 

 getting desired information. 



Petroleum and natural gas. — In recent years the search for new 

 supplies of petroleum and natural gas has become increasingly the 

 task of the geologist and the geophysicist. In this task paleontology 

 has acquired greater economic interest and importance than in any 

 other branch of the mineral industry. Fifty years or so ago, who 

 would have thought that a matter of prime importance to a great 

 industry would be the stratigraphic position and depth below the sur- 

 face of certain beds of rock whose chief characteristic is their content 

 of tiny fossils? Yet now in certain oil-bearing regions such beds serve 

 to outline, or help outline, the shape, size, and position of oil and gas 

 pools. Our knowledge of subsurface geology, on which the search 

 for oil now largely depends, has been built up by the geologist, patiently 

 gathering and comparing data from well cuttings and cores, identifying 

 fossils — including many of microscopic size — determining mineral 

 particles and preparing the maps and sections on which the collected 

 data are assembled and summarized. 



The geophysical prospecting now in wide use in the search for oil 

 and gas derives much of its usefulness from the great body of data 

 assembled and integrated by geologists. The effectiveness of geo- 

 physical combined with geologic methods has been well shown in 

 many parts of the United States, especially in Texas and Louisiana 

 near the Gulf of Mexico, where many oil fields and salt domes have 

 been thus located, in California, where oil pools are being tapped at 

 great depths, and more recently in the central Illinois basin. The 

 geologist is indispensable to the oil industry. The literature on geo- 

 physical prospecting is increasing at a rapid rate. A quarterly 

 Geological Survey bulletin of about 300 abstracts is now required 

 merely to outline these publications. 



The contributions of the petroleum geologists to geologic literature 

 and philosophy have greatly stimulated interest in the deeper rocks and 



