PETROLEUM. 
23 
The natural gas produced is of two types according to whether it 
carries a conspicuous burden of gasoline vapor or is lean in this con- 
stituent. The first type, as may be surmised, flows from an oil- 
productive stratum and is called “ wet ” or casing-head gas, since it 
makes its appearance from the casing-heads of oil wells. The second 
type is termed “ dry 55 gas, and comes from portions of porous rock 
formations practically free from oil ; it is produced through gas wells 
more or less independently of petroleum output . 1 
While not vital to the country, because its use may be supplanted 
by other types of fuel, natural gas is of considerable commercial im- 
portance, as shown in the accompanying table : 
Relative commercial importance of natural gas, expressed on a per capita basis 
for 1915. a 
Consumption 
per capita. 
Value per 
capita. 
Average 
price. 
Natural gas (cubic feet) 
b 6,285 
1,818 
840 
2.8 
.9 
4.4 
$1.01 
1.65 
.08 
1.79 
1.84 
5.02 
c $0. 16 
c .91 
c .10 
.64 
d 2.07 
d 1.13 
Artificial city gas (cubic feet) 
By-product, coke-oven gas (cubic feet) 
Crude petroleum (barrels) 
Anthracite coal (tons) 
Bituminous coal (tons) 
a Figures calculated on basis of population of 100,000,000 from data published in Mineral Resources of 
the United States for 1915, U. S. Geological Survey. 
b Includes various types of artificial gas as commonly supplied in municipalities. 
c Note the marked discrepancy in price. The intrinsic value, as contrasted to the commercial value, 
is 1.5-2, l,and 1 respectively. 
d Price at mines. 
About one-third of the natural gas consumed in the United States 
is used for domestic purposes — lighting, cooking, and heating — while 
about two-thirds is burned in industrial plants under steam boilers 
and especially in metallurgical operations, glass and pottery fur- 
naces, and cement kilns, where the requirements of an intense heat 
call for gaseous fuel. In Ohio and Western Pennsylvania, in par- 
ticular, the abundant occurrence of natural gas has determined the 
location and widespread development of gas-fired industries . 2 
1 The two types of gas are gradational, not sharply distinctive. “ Wet ” gas carries 
upwards of three-fourths of a gallon of gasoline per 1,000 cubic feet of gas, while much 
of the “ dry ” gas carries only from one to two pints of gasoline per 1,000 cubic feet. 
See George A. Burrell and others, Extraction of gasoline from natural gas by absorption 
methods : Bulletin 120, Bureau of Mines, 1917. 
2 Thus Ohio and Pennsylvania are the two leading States in the manufacture of clay 
products ; the Pittsburgh district is the greatest glass-manufacturing district of the 
United States, while the iron and steel industry in the vicinity of Pittsburgh consumes 
an enormous volume of natural gas in its blast furnaces, foundries, and rolling mills. 
Natural gas has been “ the fourth element in making western Pennsylvania more lib- 
erally supplied with fuel than any other place in the world. In that region a thick 
forest covered hills which were underlain with the magnificent coal deposits of the 
Appalachian field, while farther down was the crude petroleum and the natural gas 
that drove it spurting from the orifices in the rocks.” The rising cost of natural gas, 
coming with progressive exhaustion of fields, has caused a migration in the glass- 
making industry, many plants having moved from Pennsylvania to West Virginia and 
from Indiana to Oklahoma in order to get cheaper fuel ; other plants in regions de- 
