Chap. 7] 



GRAVITATIONAL METHODS 



157 



distance as lever arm, multiplied by the angular disk displacements dip. 



Since the horizontal gravity component is given by / / cos (p c^ dr, its 



value for a given section may be obtained with the same integraph by 

 simply interchanging the z and x axes. 



American Aakania Corp. 



Fig. 7-48. Integraph for the calculation of horizontal and vertical components of 

 gravity attraction of two-dimensional bodies. 



H. Results of Pendulum and Gravimeter Surveys 



The following short description of results of gravity surveys is not in- 

 tended to convey the idea that a limited amount of such work has been 

 done. Owing to the fact that in the earlier days of geophysical prospect- 

 ing the pendulum method was less widely used than the torsion balance 

 and because of the comparatively short length of time that gravimeters 

 have been employed, not much data on results have found their way into 

 the literature. Much information on gravity variations over known 

 geologic structures has been accumulated in the course of calculations of 

 relative gravity from torsion balance gradient observations. These in- 



