210 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 lime- 

 stone ; 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 lateral 

 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 spe- 

 cial limestone, but that they had been sublimed and segregated 

 through the heat of intrusive trap. R. E. Rogers expressed him- 

 self 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. ^ 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 sub- 

 limation or by slower electrical causes. - 



I See Am. Jour. Sci., Series I., Vol. 47, 1844, p. 106. 

 = Am. Jour. Sci., Series I., Vol. 43, 1842, p. 69. 



