GRAVITATIONAL METHODS 



341 



magnitude of the R vector is the resultant of these two components, symbol 

 \R\. 



The angle 2a is measured from the north, clockwise to the plotted 

 R-line, and recorded. In Figure 192, the values for stations 3 for the R-line 



ijyj- 



Fig. 191. — Plotting curva- 

 ture value, R. 



Fig. 192. — Curvature quantity: 

 R-line value at Station 3, Wild 

 Horse Park. Magnitude of i? r= 

 49.0, the angle 2\ = 308° and 

 X = 154°. 



are plotted ; the components of curvature quantity are Ua = —29.2 E. and 

 for 2 Uxy = — 39.3. After the magnitude of the R-line and the angle A 

 have been determined, the R-line is divided into two equal parts by the 

 station and plotted at the angle X from the N. In the case of Station 3, 

 this would be a length of 24.5 on each side of the station as center and 

 at an angle of 154°. (See Figure 193.) 



GRADIENT-j/ 



Fig. 193. 



-Plotting of curvature 

 quantity. 



Fig. 194.- — Complete represen- 

 tation of the gravity values at 

 Station 3. Scale 1 mm. = 1 £. 



The final form of the gradient and curvature values to be shown on 

 the map is illustrated in Figure 194. 



The Gradiometer. — The gradiometer is essentially a modified torsion balance 

 so constructed that the torsion wire is acted on by a gradient torque only. The beam 

 system of the gradiometer is shown schematically in Figure 195. Three small masses 



