The Encyclopedia Americana, Volume 7Grolier Incorporated, 1990 - Encyclopedias and dictionaries |
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Page 142
... natural gas sent their costs upward sharply . Under these conditions , interest in coal production and coal research ... natural gas resources began to be exploited rapidly . See also GAS , FUEL - Manufactured Gas and History of the Gas ...
... natural gas sent their costs upward sharply . Under these conditions , interest in coal production and coal research ... natural gas resources began to be exploited rapidly . See also GAS , FUEL - Manufactured Gas and History of the Gas ...
Page 618
... natural resources for future generations . The central purpose of most conservation activity is the perpetuation of ... Natural Resources ? The earth's sur- face provides the stage for human life , and the useful elements of the natural ...
... natural resources for future generations . The central purpose of most conservation activity is the perpetuation of ... Natural Resources ? The earth's sur- face provides the stage for human life , and the useful elements of the natural ...
Page 619
... natural resources . Today , more than 75 minerals are used in significant quantities by modern in- dustry ; less than a century ago the figure was no more than 25. Moreover , the efficiency gained through large - scale mining operations ...
... natural resources . Today , more than 75 minerals are used in significant quantities by modern in- dustry ; less than a century ago the figure was no more than 25. Moreover , the efficiency gained through large - scale mining operations ...
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