Chap. 12J 



MISCELLANEOUS GEOPHYSICAL METHODS 



883 



nated by employing a V.T. oscillator, as shown in Fig. 12-6. Another 

 feature of this apparatus is an output stage in which the pulses are rectified 

 and passed into a tank circuit containing two AO-nf condensers and a 

 counting-rate meter. The Geiger counter and first amplifier tube are 

 carried in an extension handle connected to the remainder of the instru- 

 ment, so that the ground radiation at any point may be readily in- 

 vestigated. 



-^aaaAaaa— ' — '■ -^^ — (/) — ^AA/VWV — ■' 



I ^AAA^AA/V 



±:C, 



AA/WWW 



Fig. 12-6. Portable Geiger counter detector, with oscillator replacing high- 

 voltage batteries (after Kaiser). Ci = 500/hm/; C-i = 0.01 /x/; C3 = 0.02 ju/; C4 = 0.01 

 ill/; C5 = 5/x/z/; Ce = 0.5m/; Ci = 80 m/ (midget electrolytic); A^ = G.E.-CD-1010-Cl 

 neon lamp, 40 milliwatt; Ti, Tz = telephone jacks; TR = output transformer, 1:6; 

 GT = Geiger-Mueller tube; M = 0-200 or 0-100 microammeters; Li, Li, L3 = oscil- 

 lator air-core transformers. 



D. Results and Interpretation of Radioactivity Measurements 



Measurements of radioactivity have been made (1) in wells, to indicate 

 oil sands or formation boundaries; (2) underground, to locate concentra- 

 tions of radioactive ores; (3) at the surface, to locate radioactive ores; 

 (4) to locate radioactive springs; (5) to locate oil; (6) to map faults and 

 contacts; and (7) to locate mineral veins. These measurements have been 



