50 C. E. VAN ORSTRAND 
W. on the outer edge of the dome. Not only is the great range in values 
of 1/b in agreement with our hypothesis, but the further fact that abnor- 
mally high temperatures are found immediately above the granitic mass 
leaves little to be desired in explanation of the observed distribution of tem- 
peratures. 
On account of the great depth to the crystalline rocks at Long Beach, 
possibly 20,000 feet, it seems unlikely that depth to the crystalline rocks, 
which appears to be an important factor at Salt Creek and in Central Okla- 
homa, will provide an explanation of the temperature variations found in 
this field. Steeply dipping strata are present, but about the only other pos- 
sibilities to which we can appeal are recent erosion, abnormal thermal con- 
ductivities and generation of heat in the strata. I shall not here attempt to 
discuss the merits of these possibilities. 
To estimate the effects of radioactivity on the isogeotherms at Long 
Beach, let us expand Eq. (4) into the form 
H B 
b= s[i+cat---| 
2 2 
and then putting 
H = 360 feet = 10973 cms w=1.5 X 1078 
a = 0.00036 a’ = 0.00006 & = 0.004 
we have 
H w 
h = — = 5486 cms B = ————— = 6.25 X 1078 
2 2k(a — a’) 
and the new value of h is found to be 5488 cms an increase of only 2 cms. 
Using Joly’s® recent value, w=42.1X10-“, we have 
B=1.75 X 10-7 hk = 5491 cms 
an iucrease of 5 cms. The resulting change in d (Fig. 9) is obviously negligi- 
ble, consequently Eq. (6), which contains (d), remains unchanged. 
Another method of procedure consists in computing the rise in the 0°F 
isotherm beneath the apex of the hill. Putting x =o and z=o in (6) and using 
the same constants as before, including Joly’s value of w, we find 
v+ Av 
H 
(ie) (Eo a 
ae 
2.617 + 0.005 = 2.622°C 
HT 
from which it again appears that the term due to radioactivity is negligible 
in comparison with the observed variations in temperature across the struc- 
ture. 
8 John Joly. The surface-history of the earth. Second edition, p. 60 (1930). The Clarendon 
Press, Oxford. 
194 
