CORRELATION OF ISOGEOTHERMAL SURFACES 51 
Some GENERAL SUGGESTIONS 
Our observations are not yet sufficiently accurate nor sufficient in num- 
ber to permit making definite generalizations. The chief source of inaccuracy 
is unstable temperature equilibrium in wells. Notwithstanding these irregu- 
larities, however, the observations show conclusively that the isogeothermal 
surfaces rise in passing over a large number of salt domes and anticlinal struc- 
tures. There is no well established evidence of depressed isogeotherms in any 
oil field, but in a considerable number of fields, the rise in temperature is not 
very marked. In general, the observations suggest the conclusion that a rela- 
tion exists between the high temperatures and positive gravity anomalies 
that prevail over the crests of many of the oil field anticlines. 
The causes of temperature variations given in the preceding paragraphs 
are to be regarded merely as preliminary suggestions. The complete explana- 
tion will undoubtedly involve isostasy, geological history, and the sources 
of the earth’s internal heat. 
195 
