434 



MAGNETIC METHOD 



[Chap. 8 



thinning and tightening of the water-bearing beds occurred on magnetic 

 highs so that chances of increased water supply were greater on the 

 flanks and in the lows, A report by Kelly states that a subsurface 



■noor ■ 



-Aoor 



*t2o<a 



*aoor 



*4oor 



t09 



-40or 



:> ■ J- A- 



''Tmww. 



fm^77//^ 



^ 



200 



300 



400 m 



Fig. 8-76. Location and thickness determination of basalt flows for building and 

 road material (after Ahrens). 



structural trough was mapped magnetically by Jakosky to investigate 

 water supply conditions on the Kaibab plateau. 



2. In the location of construction materials, magnetic methods have con- 

 siderable chance of success in outlining occurrences of igneous rocks suit- 



208 Min. and Met., 17, 10 (Jan., 1936). 



