808 



ELECTRICAL METHODS 



[Chap. 10 



the intersection with the vertical from A in B. B is then a point on the 

 index curve. Other points are similarly located. The apex of the index 

 curve is the conductor. Actually, index curves are more complex, de- 



Line 45 



Line 46 



Line 49 



Line 51 



Line 53 



Line 54 



JBOf 500e 



Line 55 



Line 17* 



Fig. 10-125. Index curves obtained in Zeehan copper-nickel field (Tasmania) by the 

 high-frequency method (after Edge and Laby). 



pending on the shape of the conductor. Furthermore, a considerable 

 modification is introduced because a refraction of the wavefront W occurs 

 at the earth's surface. ^"^ 



»" Ibid. 



