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THE JOURNAL OF GEOLOGY.

forms. From this and other statements it is plain that he did not discriminate between the different limestone formations which we now recognize in the Mississippi valley. He made a special examination of southeastern Missouri, and expresses the conclusion that the disseminated lead ore of Mine la Motte must necessarily have been deposited at the same time as the limestone; also that the veins of this country undoubtedly descend very deep towards the central part of the earth; and, finally, that the ore in these veins was "projected from below," the laterial veins from a main lode being compared to the branches of trap dikes, while the red clay is paralleled by the red mud accompanying volcanic eruptions in Sicily. The iron ores of Missouri, he also states, are of direct subterranean origin and fill veins or fissures produced by dislocation.

Though such ideas seem extravagant to us now, they were discussed and believed by scientific men of the day. Thus, in the proceedings of the fifth session of the American Association of Geologists and Naturalists, after a statement of Professor J. Locke's, that the Trenton age of the rocks containing lead ores of the upper Mississippi had been determined, Dr. Houghton replied that he did not think the ores were confined to any special limestone, but that they had been sublimed and segregated through the heat of intrusive trap. R. E. Rogers expressed himself in support of a similar explanation. In answer to this Dr. H. King sagaciously remarked that no volcanic or igneous action had taken place in Missouri or elsewhere in this lead region, and thus could not have influenced the segregation of the lead; that the subjacent rocks were not traversed by dikes, and that the lead ore was imbedded in the rock, like masses of chert.[1] Again Mr. J. T. Hodge, in 1842, in a long article on the Missouri and Wisconsin-Iowa mining regions, after describing copper deposits of Missouri, concludes that the copper ore had apparently been projected from below, either melted by sublimation or by slower electrical causes.[2]

  1. ↑ See Am. Jour. Sci., Series I., Vol. 47, 1844, p. 106.
  2. ↑ Am. Jour. Sci., Series I., Vol. 43, 1842, p. 69.
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