100,000 



10,000 



1000 



100 



10 — 



BACKGROUND 



0.05 0.10 0.15 0.20 0.25 



FREQUENCY (CPM) 



0.30 



0.35 



Figure 27. Power spectrum from successive half-minute readings of the depth of the 

 79 C isotherm (Section 0, fig. 15). The peaks and zones of higher power are indicated. 



55 



