nder local conditions--including considerations of labor
and climatic and topographic conditions,--the probability of increase or
decrease in demand for the product, the possible changes in
metallurgical or concentrating practice (such as those which made
possible the mining of low-grade porphyry copper ores), the size of
already available reserves, and the mining laws in relation to
ownership and regulation. Most of these factors are discussed at some
length on other pages. After looking into the economic conditions
limiting the chromite, nickel, or tin developments in the United States,
the explorer might hesitate to proceed in these directions,--for he
would find that past experience shows little promise of quantities and
grades equivalent to those available in other countries, and that there
is little likelihood of tariffs or other artificial measures to improve
the domestic situation. Before and during the war, commercial conditions
might have shown the desirability of hunting for pyrite, but more recent
developments in the situation cast some doubt on this procedure. To go
ahead blindly in such a case, on the assumption that the pyrite market
would in some fashion readjust itself, would not be reasoned
exploration. Again, in considering exploration for copper, account
should be taken in this country of the already large reserves developed
far in advance of probable demand, which require that any new
discoveries be very favorably situated for competition. In oil, on the
other hand, a very brief survey of the economic factors of the situation
indicates the desirability of exploration. The comparative shortage of
lead supplies at the present time suggests another favorable field for
exploration.

In short, before actual field exploration is begun, intelligent
consideration of the economic factors may go far toward narrowing the
field and toward converging efforts along profitable lines. Looked at
broadly, this result is usually accomplished by the natural working of
general laws of supply and demand; but there are many individual cases
of misdirected effort, under the spell of provincial conditions, which
might easily be avoided by a broader approach to the problem.

GEOLOGIC FACTORS IN EXPLORATION

Coming to the geological aspects of exploration, the procedure in its
early stages is again one of elimination. Oil and coal, for instance,
are found in certain sediments of certain ages, and one would not look
for t