r to the
oil beds and in the use of artificial pressures and better pumping.
"Casing-head gasoline" is being recovered to an increasing extent from
the natural gas which was formerly allowed to dissipate in the air.

Minute division of the ownership of a pool, with consequent
multiplication of wells and unrestricted competition, tends to gross
over-production and highly wasteful methods. The more rapid exhaustion
of one well than the others may result in the flooding of the oil sands
by salt waters coming in from below. Various efforts have been made
toward a more systematic and coordinated development of oil fields.

In general, the organization and technique involved in the development
of an oil field are improving in the direction of extracting a greater
percentage of the total available oil.

Better methods of refining the oil, and the refining of a larger
percentage of the crude oil, make the oil more available for a greater
variety of purposes and therefore more valuable. Great advances have
been made along these lines, particularly in the application of the
"cracking" method for a greater recovery of the more valuable light oils
at the expense of the less valuable heavy oils. Similarly, modifications
of internal combustion engines will probably permit the use, in an
increasing number of cases, of products of lower volatility than
gasoline.

One of the conservational advances in coming years will probably be a
restriction in the amount of crude oil used directly for fuel and road
purposes without refining. These crude uses cut down the output of much
desired products from the distillation of the oil. Various other
restrictions in the use of oil have been proposed, such as the
curtailment of the use of gasoline in pleasure cars. The gasless Sundays
during the war represented an attempt of this kind. In general, it seems
likely that such restrictions will come mainly through increase in the
price of oil products.

The substitution of oil from oil shales, and of alcohol for gasolene,
already mentioned, will be conservational so far as the oil is
concerned, though perhaps not so in regard to other elements of the
problem.

GEOLOGIC FEATURES

=Organic theory of origin.= According to this theory, accumulations of
organic materials in sedimentary beds, usually muds or marls, have been
slowly altered and distilled during geologic ages; the products of
distillation have migrated chiefly upward to porous strata l