542 



SCIENCE 



[N. S. Vol. LI. No. 1326 



2. In general, the more widespread the 

 oceans the less sinuous the isotherms. 



3. During periods of more nearly universal 

 oceans, the closer the parallelism between iso- 

 therms and parallels. 



It would appear that the logical conclusions 

 to be drawn from the two immediately pre- 

 ceding quotations, providing we may take for 

 granted a knowledge of the general conditions 

 of past climates, are as follows : 



1. The belt between the parallels 20° and 50° 

 north latitude was, during the periods when 

 the petroleum of the zone was forming, some 

 definite temperature zone the boundaries of 

 which, the average annual isotherms, were es- 

 sentially coincident with the parallels. 



2. The temperatures of this zone very likely 

 fluctuated within a single period and showed 

 more or less marked differences from period 

 to period. 



3. The average of the fluctuating tempera- 

 tures for this zone was not necessarily the 

 same as that of this belt for the present time, 

 viz., 40°-70° F. 



4. The only reference to the formation of pe- 

 troleum in this zone at present day tempera- 

 tures (the Mediterranean Sea) does not illus- 

 trate the manner in which petroleum is 

 formed. 



The obvious inference of these conclusions 

 is that could we determine the exact tempera- 

 ture conditions under which petroleum is 

 formed there would be available another means 

 of testing the temperatures of the various areas 

 in which the peitroleum was formed, during the 

 periods when it was forming. In other words, 

 some estimate could be m.ade of the average 

 temperature of the " petroleum zone " — that 

 belt bounded by the parallels 20° and 50° 

 north latitude — during the "petroleum pe- 

 riods." 



There is one more point on which the pres- 

 ent writer's view was, perhaps, not adequately 

 stated, although his intention would seem to be 

 clear. The following is from Dr. Schuchert's 

 criticism : 



. . . The writer also knows that hydroeaiibons 

 have accumulated in large amounts in seas within 

 the tropics, yet seemingly the amount ia far the 



greatest in whajt as now the north temperate zona. 

 That this zone has the greatest amount of pe- 

 troleum is apparently due wholly to the greater 

 land masses here, along with the necessary storage 

 strata accompanied by the proper amount of de- 

 formation. 



Even if Mehl's suggestion were correct, and we 

 should accordingly think of next exploiting the 

 temperature region of the southern hemisphere, we 

 must not overlook the fact that the northern hemi- 

 sphere is a land hemisphere, while the southern 

 one is a water hemisphere, and therefore has greatly 

 reduced continents. 



To quote from the article on " Geographic 

 Distribution " : 



Eegardless of the lack of thorough prospecting, 

 however, there is reason to believe that of the three 

 zones, the equatorial belt between the twentieth 

 parallels and adjacent belts in the northern and 

 southern hemispheres extending north and south to 

 the fiftieth parallels, the northern belt will, when 

 investigations are carried to completion, be found 

 the more productive. Tor instance, one may safely 

 assert that, all other factors being equal, the 

 amount of petroleum underlying a given area ia di- 

 rectly proportional to the size of that area. It is 

 evident that in the area of exposed lands neither 

 the southern nor the equatorial belts compare fav- 

 orably with the northern zone. 



And again, in summarizing: 



If we may grant, then, that within a limited 

 zone, the equatorial belt, conditions have been un- 

 favorable for the formation of accumulations of 

 petroleiun, on the average, it is logical to seek a 

 belt in the southern hemisphere suitable for such 

 deposits, to correspond with the belt in the north- 

 ern hemisphere. Were the temperature factors 

 alone to be considered, there is little doubt but that 

 much might be expected from the southern zone. 

 It has already been pointed out, however, that the 

 area of exposed land within this zone is relatively 

 small and of this a very large proportion consists 

 of Pre-Cambrian or igneous rocks. Apparently 

 little more is to be expected from the southern 

 belt than from the equatorial zone. 



As the writer stated in the article quoted by 

 Dr. Schuchert, it was hoped " that the specula- 

 tions would call forth a discussion of the prin- 

 ciples involved and possibly stimulate investi- 

 gations in the several branches of science in- 

 terested." He was much surprised to learn 



