370 



THE CBYSTAL PALLS lEON-BEAEING DISTEICT. 



In this figure it is instructive to notice the small dip angles in the 

 sections east of the end of the syncline. In the first of these the dip 

 curve shows a hollow near the axis of the fold or angles of depression less 

 than the normal. This is easily understood iipon considering that, since 

 the surface covering is here small, the vertical component of the rock 

 force becomes very small at these stations con:ipared with the horizontal 

 component. 



For an eastward-pitching syncline it is obvious that the facts will be 

 entirely similar to those stated above, except that the deflections of the 

 horizontal needle will be toward the east instead of toward the west. This 



I y 



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 / 



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/ ^1 1, 







J 11 



Fig. 22 Magnetic map of tlie Groveland Baain. 



is also well shown at the western end of the Groveland basin in fig. 22. 

 This basin does not show the phenomena of two lines, however, from the 

 fact that it is so naiTOw and shallow that it does not include in its interior 

 any overlying nonmagnetic matei'ial, and there is accordingly no separation 

 of its rims. 



2. PITCHING ANTICLINES. 



In the cases of pitching anticlines (fig. 23) the sequence of observa- 

 tions in the area of separation of the rims is very similar to that of pitching 

 synclines. In the zone of coincidence the structural difference in the two 

 cases is that the material does not come to an end, but continues as one 

 band, which, as the axis sinks, is progressively buried to a greater depth. 



