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a half inches long, somewhat resembling C. gyratus, but with a 

 flat spire. Mr. Lyell had placed this formation in the Eocene 

 series ; but Mr. C, judging from the fossils, could not agree with 

 him. Above, and upcn this formation, imbedded in clay-marl, 

 he had found fragments of fossil bones. From the rounded 

 form, compactness of texture, and the eccentric and concentric 

 circles of the cross sections of the ribs, he considered them to 

 belong to the Zeiighdon. 



Prof. H. D. Rogers asked the attention of the Society to 

 some phenomena noticed by him in the mineralogy and 

 geology of the southern shore of Lake Superior. He also 

 exhibited specimens of sandstones and trap rocks, and their 

 concretionary geodes, from the same region. 



The first feature alluded to by Prof Rogers was the mode in 

 which the metallic copper of Kewenaw Peninsula is often surround- 

 ed by certain minerals, its frequent associates. At the Eagle River 

 mine, and elsewhere, the metalliferous rock is not, as sometimes 

 supposed, a real trap rock, but a mixture of trappean matter, and 

 that of the red sandstone formation, more or less baked and 

 modified by intense igneous action. These semi-fused materials, 

 in crystallizing, have very frequently resulted in the following 

 curious arrangement : the crystalline metallic copper occupies 

 the centre of globular and variously formed concretions ; cal- 

 careous spar usually, but not always, invests the copper ; and 

 very generally the exterior of the kernel is pure crystalline 

 chlorite. , Specimens were shown proving this to be the common 

 order. These nodular lumps are dispersed through a base which 

 exhibits a sort of pasty mixture of softened red shale and true 

 trappean matter ; and many of them are so surrounded as to 

 indicate them to be true segregations from this semi-igneous, 

 semi-aqueous compound. Upon this view, we may derive the 

 magnesia of the chlorite, which could not originate from the red 

 shale, cither from the hornblende of the trappean matter, or from 

 a sublimation of magnesium, in the form of vapor, penetrating to 

 the outer crust at a moment of volcanic outburst, as potassium 

 and sodium are conjectured to do, according to Forchhammer, in 

 the generation of some granitic rocks. 



Evidence was then presented of the production of a portion, at 



