the next nine years alone we shall produce an equal
quantity again. The causes of such rapid growth are many. One is the
great increase in the use of some of the products, such as gasolene,
which has increased many fold since the automobile became popular.
Another, and the greatest cause, is the ease with which any quantity of
oil can be sold for cash at any time, and at prices much above the cost
of production.

Another reason is based upon the nature of the product. In pumping from
one well oil is apt to flow in from other leases, under other farms, and
exhaust them without the holders of those leases having received any
compensating benefit. It is therefore necessary for each lessee to get
his share before it flows away. Under these circumstances, it is
impossible to prevent an entire field from being drilled over very
rapidly, unless there is a combination of all the interests; or unless
the law limits the amount that each producer shall extract per acre
within a given time.

Pennsylvania and New York have declined to one-third their former value
and yet it is only seventeen years since they reached their highest
point. This would seem to indicate that the life of that field will not
exceed ten years. West Virginia is producing only a little more than
half its former yield and is rapidly declining. Ohio and Indiana are
declining more rapidly than Pennsylvania. Texas is also in the rapidly
declining class, and in Kansas the production is only a fraction of
what it was formerly. On the other hand, Illinois, Oklahoma, and
California can be expected to increase steadily for several years.

Taking into account all these factors, it is estimated that the entire
supply now known to exist would be exhausted before the middle of the
present century. It appears more probable, however, that increasing
prices long before that time will help to conserve the supply; and that
petroleum will be produced for a long time to come, though not in
sufficient quantities for industrial and general use.

The principal uses of petroleum are for burning as crude oil in furnaces
and under boilers, particularly in locomotives. The refined products
have various uses. Probably the most important is the lubricating oil.
This is necessary in the development of all kinds of power. At least
one-half pint of lubricating oil is used for every ton of coal consumed
for power. All engines, all street and steam railways, steamships,
sewing-machines, cl