Figure 25-3. Wulff Polar (equatorial) stereographic net drawn to 2° intervals. 



through the hemisphere perpendicularly to a vertical axis, these will project into 

 the equatorial plane as concentric circles, forming the Wulff polar stereographic 

 net (fig. 25-3), which is useful in some structural problems. 



APPLICATIONS OF One of the basic problems of structural ge- 



STEREOGRAPHIC NET IN ology is the determination of the line of in- 

 STRUCTURAL GEOLOGY tersection of two planes (Bucher, 1944; 



Nevin, 1949; Wallace, 1950; Phillips, 1954). 

 Intersection of Two Planes (1) A fault plane or a vein may intersect a bed- 

 ding plane; surface or subsurface attitudes of 

 beds may be known on opposite flanks of an anticline. In these instances it may 

 be desirable to find the attitude of the line of intersection of the planes involved. 



534 



