PETROLEUM. 
49 
especially these in Mexico, if fully available and barring inter- 
national complications, would put off the period of petroleum ex- 
haustion in the United States for only a matter of say a couple of 
decades; hence their presence does not change the urgency of the 
domestic issue. Moreover, the high-use employment of these de- 
posits — the output is now used dominantly for fuel purposes — 
would be to the best interest of Great Britain, the United States, 
and other countries using the output, not to mention the advantage 
accruing to the producing Republics themselves. Indeed, it would 
seem, so far as such things may be determined from the outside, 
that Mexico would take the lead among the Republics concerned in 
developing a policy in regard to petroleum development that would 
prevent production from exceeding the demand for the high-use 
products, as this legitimate drain may be expected largely to exhaust 
the supplies within a generation or two. 
On the whole, it would appear to be for the good of all con-i 
cerned that the Mexican deposits should not be more wastefully ex- 
ploited than those of the United States, for the world needs the 
full service of the aggregate supply. 
DEVELOPMENT OF OIL SHALES. 
Granted the utmost in the development and use of the remaining 
supply of petroleum, economic pressure from oil shortage will still 
be not far distant. Attention turns, therefore, to sources of supply 
other than the porous rocks of oil fields thus far exclusively exploited 
in this country. It is of great significance, therefore, that within the 
past five years geological explorations on the part of the United 
States Geological Survey have definitely established the existence of 
vast areas of black shale in Utah, Colorado, and Wyoming, much of 
it capable of yielding upon distillation 1 around 50 gallons of oil, 
3,000 cubic feet of gas, and IT pounds of ammonium sulphate 2 — the 
whole constituting an oil reserve aggregating many times the original 
supply of petroleum. 3 
1 Oil shale is not supposed to contain petroleum, but upon the application of heat, it 
is thought, organic compounds present react to form an oil resembling petroleum from 
which can be obtained essentially the same products that petroleum itself yields. But 
this matter needs further investigation, as it is by no means certain that some oil 
shales, at least, do not actually contain petroleum as such. In either event, however, 
shale oil is practically the equivalent of petroleum. 
2 The occurrence and distribution of these shales, together with the results of distilla- 
tion tests, are given by Dean E. Winchester, Oil Shale in Northwestern Colorado and 
Adjacent Areas : Bulletin 641-F, United States Geological Survey, 1917, pp. 152-155. 
Yields up to 90 gallons of oil, 4,294 cubic feet of gas, and 34 pounds of ammonium 
sulphate were obtained from certain samples. The figures cited in the text, however, 
represent commercial averages typical of workable areas. 
3 It is estimated that the oil shales of Colorado alone underlie 1,400 square miles, 
with an average aggregate thickness of 53 feet, and are capable of yielding 20,000,000,000 
barrels of oil, an amount approximately twice as great as the original petroleum reserve 
in this country, together with 300,000,000 tons of ammonium sulphate, valuable as a 
fertilizer, nearly 900 times the domestic consumption of that substance in 1915. The 
important r61e of ammonium sulphate in modern affairs is shown on the chart accom- 
panying Bulletin 102, part 2, of this series. 
