62 
MAUKICE G. MEHL 
by the thick accumulations of soil on these lands. Again, from 
the standpoint of the inadequacy of the check on the destruction 
of the fatty base by bacteria, the equatorial belt should be less 
favored in accumulations of petroleum. This too is largely a 
function of temperature, for the slow rate of sedimentation is in 
no small measure due to the luxuriant growth of vegetation 
which prevents the free wash of the rock waste from the 
land. 
Aside from its function as a check to the activities of denitri- 
fying bacteria, the rate of accumulation of inorganic sediments 
is of further importance in the formation of petroleum. Very 
often the rapid decay of organisms is pointed to as illustrating 
the manner in which petroleum is formed. In certain parts of 
the Mediterranean Sea, for instance, the accumulation and decay 
of organic detritus is so rapid that the lower levels of the water 
are filled with scattered globules of oil. Instead of illustrating 
how petroleum is formed, however, it points to the effective 
manner in which fatty matter is ordinarily separated out from 
accumulating sediments. Certainly, the globules of oil which 
are escaping into the water offer no suggestion of being retrapped 
and converted into petroleum. It is only that part of the organic 
matter which is converted into oil so slowly that the accumu- 
lating sediments form a sufficient thickness and suitable suc- 
cession to retain it against the tendency of the associated waters 
to drive it off, that may become petroleum. 
If we may grant, then, that within a limited zone, the equato- 
rial belt, conditions have been unfavorable for the formation of 
accumulations of petroleum, 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 northern 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 ex- 
posed land within this zone is relatively small and of this a very 
large proportion consists of Pre-Cambrian or igneous rocks. Ap- 
parently little more is to be expected from the southern belt 
than from the equatorial zone. 
