Subsurface Methods as Applied in Geophysics 1119 



prospecting. Suggest regions where correlation shooting will be 

 successful. 



15. Discuss differences between refraction and reflection methods of pros- 

 pecting. List advantages of the reflection method. 



16. What is meant by the "weathered layer"? 



17. Discuss relationship between the geologic history of an area and 

 the assumptions to be made concerning dispositions of the iso-vel- 

 ocity surfaces. 



18. Calculate throw of the Hunton Lime in figure 580 if average velocity 

 function from datum is 7,000 + 0.7z feet per second, and if corrected 

 reflection time to the Hunton for shot-point 180 S-E is 1.422 seconds 

 and for shot-point 190 W-E is 1.233 seconds. Assume vertical re- 

 flections. 



19. Sketch equi-potential lines between a source and sink of current for 

 homogeneous ground. Insert a conductive body between power elec- 

 trodes and again sketch distribution of equi-potential lines. 



20. Indicate applications of resistivity measurements to problems of the 

 mining and petroleum industries, and in civil engineering work. 



