56 
MAURICE G. MEHL 
In the following paragraphs the writer attempts to correlate 
certain facts and observations which may assist in the solution 
of some of the problems in the geographic distribution of petro- 
leum. There is no attempt at exhaustive treatment and little 
or no claim is made for originality. It is hoped that the specu- 
lations will call forth a discussion of the principles involved and 
possibly stimulate investigations in the several branches of 
science interested. It is only through the cooperation of the 
experts in these sciences that adequately supported conclusions 
as to the likely distribution of petroleum can be reached. 
Considering petroleum and the related substances as a group, 
they are among the most widely distributed minerals; there are 
but few unmetamorphosed sedimentary beds that contain no 
trace of these hydrocarbons. Small showings are found en- 
circling the globe and they extend from well toward the poles 
to the equator. Workable accumulations are much less widely 
distributed, however, and great commercial deposits are com- 
paratively rare. 
On the accompanying map, plate XII, are platted the more 
important areas of production throughout the world. It will 
be noted at once that these major accumulations, as they may 
be termed, are confined to the northern hemisphere. It will 
also be seen that none of the areas indicated extend north of 50° 
N. latitude nor south of 20° N. latitude. In fact, if one is to 
avoid extremely sinuous lines, perhaps no better boundary could 
be desired than these parallels. 
True, outside of this belt are known deposits of some magni- 
tude, accumulations that might be classed with the major fields, 
such, for example, as those of Alaska, Peru, or Ecuador. These 
and other possible exceptions, however, are in no wise comparable 
with the productive areas about the Black and Caspian Seas, 
the Lorraine district, the great belt across the United States, or 
the accumulations in Mexico. 
Attention is further called to the general correspondence be- 
tween the position of the twentieth and fiftieth parallels in both 
hemispheres with the average annual isotherms of 70° and 40° 
respectively. Although these parallels are, in reality, nothing 
