42 C. E. VAN ORSTRAND 
beyond which the curve is slightly convex towards the depth axis. Another 
point of interest is the fact that the excess of annual mean soil temperature 
just beneath the surface of the ground over annual mean air temperature 
just above the surface of the ground (a-b, Fig. 6), amounts to more than 
7°F. This large discontinuity in the depth temperature curves at the surface 
of the ground is typical of oil field areas in Southern California. 
CORRECTION FOR SURFACE TOPOGRAPHY 
The longitudinal section of the Long Beach field, Fig. 7, shows at once 
that the total rise in the isothermal surfaces as they pass over the dome and 
beneath the hill can not be explained on the basis of normal cooling; for, the 

360 feet =/09,73 meters. 
3 8S =/,385 feet «42215 meters. 
(39EGS feet «42570 meters. 
= 0257760 
0.000,338.412°C per cm. 
°C in 29SS meters=1F in SIE: 
0.00005 °C. per cm. 
@°C 19 200 meters =/°F i HAS feet 
O85225/ c,=/64(654 cms per F 
¢ Hd=33B,095,783 

nun 
() SEA LEVEL, /N FEET 


k 
&LEVATION ABOVE (OR BELOW, 
9920 

wz 
DISTANCE FROM CENTRAL PLANE OF RIDGE, IN FEET 
Fig. 8. Transverse section of Long Beach Dome showing computed isotherms. 
fact that the thermal surfaces are steeper and show a greater rise from the 
lowest to the highest points than the topographic surface above them proves 
conclusively that we are not dealing with a normal flow of heat towards the 
surface of the earth. In order to form an estimate of the discrepancy resulting 
from this abnormality, use will be made of the equations given by Lees.§ 
Referring to Fig. 8, let the axis of x be taken at sea level, with the origin o 
directly beneath the apex of the symmetrical hill. Elevations above sea level 
are negative; below, positive. As the hill or mountain is assumed to be a ridge 
which is very long in comparison with its cross-section, the problem is re- 
duced at once to the flow of heat in two dimensions. The fundamental equa- 
tion to be solved is 
02y 07 
Ox? Oz? 


2H) (1) 
seis 
5 Charles H. Lees, On the shapes of the isogeotherms under mountain ranges in radioactive 
districts. Proc. Roy. Soc. London A83, 339-346 (1910). 
186 
