CHEMICAL METHODS 



951 



A uniform grid was not used in conducting this survey. Instead, advan- 

 tage w^as taken of the network of roads which covers the area, thus permit- 

 ting the sampHng of a large region within a relatively short period of time. 

 A uniform grid may have produced a more outstanding pattern. This 

 procedure could not be followed because of the limited time available for 

 conducting this survey. 



Fig. 585.— Geochemical survey of the Heidelberg Area, Jasper County, Mississippi. Field Develop- 

 ment as of March 20, 1945, is indicated by well symbols. (Horvitz, Geophysics, October, 1945.) 



Figure 585 shows the development of the Heidelberg Oil Field as of 

 March 20, 1945, It is apparent that the geochemical data predicted the 

 development rather well. 



Soil Analysis for the Non-Volatile Constituents. — Close to the 

 surface of the earth, mixtures of liquid and solid materials are present in 

 appreciable quantities, and significant concentration patterns are often 

 indicated by their determination. The concentration of these liquid and 

 waxy materials decreases very rapidly with depth ; therefore samples are 

 usually collected from the top few inches of soil. Great care must be 

 exercised to avoid sampling in plowed or otherwise disturbed areas. After 

 drying, the samples are pulverized and sifted to remove vegetation. About 



