The celebrated report of Foster and Whitney on the geology of the Lake Superior land district, part II, 1851, was written, so far as concerns the iron ore of the region, by Prof. J. D. Whitney. It embraces the earliest discussion of this question, so far as the writer has observed, and can be summarized briefly as follows:
Quoting examples of the occurrence of crystals of specular and magnetic oxides of iron on the walls of volcanic craters, and in clefts and cavities where they could be attributed to sublimation from great heat, he is led to regard sublimation as one of the two factors in the production of iron ores of the Marquette district. Internal, as well as volcanic, heat was with Whitney a fundamental and active postulate in much of his geological reasoning. The other factor he supposed to have been simply . . .