354 



THE CEISTAL FALLS lEON-BEARING DISTRICT. 



It is also interesting to determine the relative values of the horizontal 

 components at the two maximum points, for different angles of dip, and for 

 different ratios of h to a — that is, for different depths of burial. Fig. 18 

 shows in graphical form these relations for all angles of dip between 90° 



and 0° for seven different ratios between h^^-^ and h rr 4a. The ordinates 



to the dotted curves (concave upward) give the relative values of the hori- 

 zontal component at the maximum point on the dip side (B maximum); 

 those to the full curves (convex upward) the vahies at the maximum point 



Fig. 18. — Curvea showing the relations between the horizontal corapoDents at the points of maximum iletlectiou, for rocks 

 dipping at various anglea and buried to various depths. 



on the other side of the rock (A maximum). These curves show that the 

 horizontal component at the B maximum is always nuiuerically much less 

 than at the A maximum, and that for moderate depths of buiial it diminishes 

 very rapidly at both points with small angles of dip. 



6. DETERMINATION OF DEPTH. 



The relations between the dip and thickness of a magnetic rock, the 

 distance between the horizontal maxima, and the depth of covering are 

 given in equation (13). By assuming numerical values for ^, and either 

 for a, the half thickness of the rock, or for d, the half distance between the 

 maximum points, it is easy to plot the curve which expresses the relations 



