RADON AND MINERAL CONTENT OF SOILS 183 
whether the parent radium has been deposited near the surface of 
the grain (secondary deposition), or whether it is distributed more 
or less uniformly throughout the grain. Naturally radium formed from 
uranium salts deposited chemically on the surface of the grains will 
have a large emanating power, while that formed in minerals in which 
the uranium was originally incorporated will have a lower emanating 
power. According to Satterly’ the emanating power of a soil may vary 
from one-sixth to one-twentieth. Consequently, the ordinates of the 
curves presented here are expressed simply as electroscope readings, 
no account being taken of the variations in emanating power of differ- 
ent soils. These ordinates are divisions per second of movement of 
the electrometer fiber multiplied by 1,000. A calibration measure- 
ment on the electroscope made by using a known quantity of radon 
showed that an electroscope reading of too, that is an actual rate of 
movement of the electrometer fiber of 0.1 division per second, was 
produced by 1,539X10 ™ curies of radon in the ionization chamber. 
The curie is the amount of radon in equilibrium with one gram of 
radium. If we assume a soil porosity of 33 per cent, 1,539 X10 /? curies 
in the electroscope would correspond to about 0.57 X10 ” curies of 
radon per cubic centimeter of soil. 
As will be seen from Figure 2, an attempt to locate the fault by 
radon measurements would be very misleading, since the radon values 
obtained at the points marked B, where there is no fault, are just as 
high as, or higher than, those obtained at A, where the fault is actu- 
ally located. 
In order further to study the radon content of soils, surveys were 
made over the South Liberty salt dome. This dome has at present 
very little elevation above the surrounding terrain. The center of the 
dome is crossed by a small river. The eastern edge of the dome is a 
producing oil field. It is claimed by Bogoyavlensky’ that an oil field 
will be indicated by a change in the radioactivity of the soil. To test 
this statement a profile was run across the producing section of the 
dome, starting from the outside edge of production and extending 
toward the center of the dome some distance beyond the producing 
area. The result of this survey is shown in Figure 3. The holes from 
which samples were taken for these measurements were 5 feet deep. 
The higher radon concentration in the producing area is obvious. 
After these results were obtained the profile was extended eastward 
1 J. Satterly, Proc. Cambridge Society, Vol. 16 (1911-12), pp. 336, 356, 514. 
2 Op. cit. 
513 
