RADIOACTIVITY METHODS 



1007 



the scale-of-two, but their sHghtly higher cost is offset by the convenience of the 

 decimal system in routine operation. 



The counting rate meters used in the laboratory are essentially similar 

 to the integrating instruments previously discussed. The integrating instru- 

 ments do not possess the inherent precision of the scaling circuit,f and 

 their use mostly is limited to special applications such as monitoring, auto- 

 matic counting, etc., where a continuous permanent record of mean values 

 is desired. 



Fig. 626. — Method of measuring approximate radio- 

 activity of rock on face of ledge. Operator notes in 

 headphones number of clicks due to Geiger tube held 

 close to rock. The number is counted against a stop 

 watch on the operator's wrist. A, G-M tube; B, exten- 

 sion cord; C, counter instrument; D, headphones. 

 (Courtesy of Geophysical Instrument Company.) 



FIELD TECHNIQUES OF RADIOACTIVITY EXPLORATION 



Reconnaissance 



Fairly indiscriminate reconnaissance of outcrops may not be the most 

 successful method of radioactivity exploration, but it is certainly the most 

 common one (Figure 626). The best instrument for reconnaissance or 

 "snooping" is a small G-M counter vi^ith earphones, of the general type 



t A. G. Bousquet, "Counting Rate Meters Versus Scalers", Nucleonics 4, No. 2, 67-76 (Feb.. 

 1949). 



