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Pittsburgh, Pennsylvania (vicinity). Montour no. 4 mine of the Pittsburgh Coal Company. Testing for gas with a safety lamp; of there is gas, the lamp will burn with a blue flame. The screening keeps the open flame confined but lets the gas in
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Credit linePittsburgh, Pennsylvania (vicinity). Montour no. 4 mine of the Pittsburgh Coal Company. Testing for gas with a safety lamp; of there is gas, the lamp will burn with a blue flame. The screening keeps t. 1942-01-01. Collier, John, Jr., Collier, John. Farm Security Administration/Office of War Information Collection, Library of Congress. Public domain.
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