10% T T 10° F ~ &> x G ~ 2 = _ 4S x Q 10 2 — So a wn S Q 0-1 9s 4 > g QO \ a ~ 8 > 2 7 107 [— : a3 ~~ x " 3.1" 8 1 ! | 0.5 1.0 1.5 2 MEV Fig. 7. Gamma-ray spectra of depth increments of old soil taken from the surface inch. The origin of each spectrum has been arbitrarily separated from the preceding one by a factor of ten to facilitate inspection of the figure. AS