From Introduction: "The investigations described in this bulletin are confined to a study of the washing characteristics of bituminous coals. The washing characteristics of coals from many of the most important coal-producing fields of the Eastern and Central States were examined."
From introduction: The district discussed in this report embraces the entire northern peninsula of Michigan and the parts of northern Wisconsin and northeastern Minnesota that were covered by a re-advance of the Superior lobe of the Labrador ice sheet late in the Wisconsin stage of glaciation.
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