Chap. 7] 



GRAVITATIONAL METHODS 



269 



sible with the instrument illustrated in Fig. 7-1026. It gives the surface 

 integrals 



// 



/sin n«^ 



d(p dr and 



// 



sm n^l , dr 

 cos n«pj r ' 



(7-96a) 



\cos n.<p\ 

 s s 



where the apparatus will take multiples up to n = 3. The first integral 

 applies in the first derivatives of gravity (horizontal and vertical gravity 



Ameriean Athania Corp. 

 Fig. 7-1026. Torsion balance interpretation integraph. 



Table 34 

 APPLICATION OF GRAVITY INTEGRAPH 



components); the second in the second derivatives (gradients and curva- 

 ture values). The factor n depends, among other things, on whether the 

 integral applies to a two- or three-dimensional body as illustrated by 

 Table 34. For three-dimensional bodies the volume integrals are reduced 

 to surface integrals by evaluating the sections of geologic bodies in various 

 azimuths, plotting the effect as a function of azimuth (polar diagram), 

 and evaluating the resulting area with the same integrometer. 



