(AND ASPHALT) 115
COAL 115
ECONOMIC FEATURES 115
World production and trade 115
Production in the United States 117
Coke 118
Classification of coals 119
GEOLOGIC FEATURES 123
PETROLEUM 127
ECONOMIC FEATURES 127
Production and reserves 128
Methods of estimating reserves 134
Classes of oils 136
Conservation of oil 137
GEOLOGIC FEATURES 140
Organic theory of origin 140
Effect of differential pressures and folding on oil
genesis and migration 142
Inorganic theory of origin 143
Oil exploration 144
OIL SHALES 150
NATURAL GAS 151
Economic features 151
Geologic features 151
ASPHALT AND BITUMEN 151
Economic features 151
Geologic features 153