48 BULLETIN 102. UNITED STATES NATIONAL MUSEUM. 
made from coal, in order to enable the product to meet standards im- 
posed by municipalities — standards in part a hold over from the days 
when the flat-flame use of gas made luminosity a necessary feature. 1 
While, broadly speaking, the use of oil in gas manufacturing is a 
degradation, the practice is not only economically justifiable but actu- 
ally desirable so long as the main outlet for fuel oil is for tiring steam 
boilers, a use still more degraded with the added disadvantage of 
offering a smaller inducement for refining. 2 
In addition to the extension of “ cracking” distillation, improve- 
ments in motor design, and widespread use of the Diesel type of motor 
to replace the oil-fired steam engine, 3 an unlimited field of advance fn 
increased value extraction opens up in connection with the building 
up of an oil by-products industry. But this matter has been em- 
phasized in the preceding pages 4 and need not be detailed again at 
this point. The greatness of the opportunity, however, should not 
be underestimated. 
Development of foreign sources of supply . — In addition to the 
domestic production of petroleum, this country since 1911 has been 
drawing upon the oil fields of Mexico at an increasing rate, so that 
in 1917 that country supplied roughly one-tenth of our needs. The 
pools of Mexico, accessibly situated in the Gulf Coastal Plain, are 
the richest in the world and are capable of a much greater annual 
production than has yet been taken from them. In fact, the output 
is mainly under the control of British and American interests, and is 
held in check, especially at the present time. In the Central Ameri- 
can region in general, there are other promising oil districts, though 
none is developed in any* way comparable to the Mexican deposits. 
It is not unreasonable to expect that further exploration and develop- 
ment will make available a reserve of oil in Mexico and Central 
America equal to the total remaining in the United States. 5 
These deposits, accordingly, offer themselves in increasing meas- 
ure to supplement a waning domestic output. Their aid should be 
accepted, but their availability is incidental upon many uncertain 
factors, and obviously it would be unwise to grow into dependence 
upon them or permit their presence to offset action regarding the 
efficient utilization of our own resource. At best, these deposits and 
1 See page 14, Bulletin 102, part 4, this series. 
2 An interesting war-time development in connection with gas oil has been the installa- 
tion of toluol-recovery plants in large municipal gas plants for the recovery of toluol 
formed from the oil in the course of gas manufacture, thus adding to the supply of 
toluol contributed by the by-product coke oven. It is a striking coincidence that both 
coal and petroleum furnish the basis for the manufacture of one of the most effective 
explosives known. 
3 Coal and hydroelectricity should also assist in replacing the oil-fired steam engine. 
4 See pages 34-35. 
6 Little in the way of petroleum imports may be expected from other parts of the 
world ; South American needs will probably more than absorb the future output of that 
continent. 
