32 C. E. VAN ORSTRAND 
solution of the problem can be obtained by constructing the isogeo- 
therms. By proceeding in this way, Strong (34) has shown that the 
general effect of a poorly conducting disk is to increase the gradients 
immediately above and below the disk. 
Let us now attempt to estimate the rate at which heat must be 
developed by chemical reactions within the disk in order to maintain 
the differences in the values of the reciprocal gradients (1/6) which 
were found at Haverhill. The mean of the two reciprocal gradients on 
the producing area is 52.15 feet per °F, which compared with the one 
35 










g=/* 10-7 Calories/Sq Cm, / Sec 
dps pe = /4286.x107 "Cent 
K=00064 p=28 C=0.25 
/Meter=328/ Feet 


TEMPERATURE - DEGREES CENT/GRADE Cvs) 
S 






2500 
DEPTH - METERS @ 
Fic. 12.—Rise in temperature due to heat source at 1,500 meters (4,921 feet). 
obtained on the nonproducing area, 55.6 feet per °F., corresponds 
with a temperature difference of 2.97° F. (1.65° C.) at a depth of 762 
meters, 2,500 feet. From the diagram (Fig. 12), (35) the maximum 
rise in temperature due to a heat source at a depth of 762 meters is 
about 1.7° C., and as is also shown in the diagram, this constant tem- 
perature difference can be maintained by the generation g of 1X1077 
calories per square centimeter per second, or, 3.16 calories per square 
centimeter per year (2,932 calories per square foot per year) in a thin 
stratum of rock. As the value, 1.7° C., is a sufficiently close approxima- 
tion to the value 1.65° C., it may be assumed that the value of ¢ has 
been determined with sufficient accuracy for our purpose. Let us now 
estimate for comparison with our calculated value of g, the quantity 
554 
