142 THE MARQUETTE IliON BEARING DISTlllCT. 



Ill the eastern p(»i-ti(>n of the district is the Mesiiard formation of the 

 Michigan survey. In this the succession comprises: (1) A lower quartzite 

 and conglomerate; (2) a dolomite interstratified with slates and cherty 

 qnartzites; and (3) an upper quartzite. The tiiie position of this forma- 

 tion is not yet determined. 



Great intrusive dikes and l)osses of altered dialiase liave liroken through 

 the Marquette series and have been the causes of minor folding in them. 

 In the upper series is also an extensive area of contemporaneous volcanics, 

 largeh' tuffs, running from north of the Saginaw mine to Champion. The 

 locus of the ancient volcano was southeast of Clarksburg. In passing east 

 and west from this center more and more waterworn sediment is found 

 intermingled with the volcanic debris, until finally the rocks j^ass into the 

 ordinary sediments of the district. 



WiNCHELL, N. H. Field observations of N. H. Wincbell in 1892. Twenty-first 

 Ann. Kept. (Teol. and Nat. Hist. Snrv. of Minnesota for 1892, Miuneapoli.s, 1893, 

 pages 80-99. 



A few hastily taken field notes and a statement clain^ing priority in the 

 discovery of the existence of two Huronian formations in the Marquette 

 district comprise the (^nly portions of N. H. Winchell's Twent}'-first Annual 

 Report that deal with the area under discussion. 



The Republic mine is placed by the author in the Keewatin fonnation. 

 With respect to the second part of the article, it will be sufficient to relate 

 that Wiuchell appeals to his discovery of the conglomerate in the Saginaw 

 mine in 1888 as evidence that he recognized the existence of two ore- 

 bearing members of the Huronian in the Michigan iron district. He omits 

 reference to the essential fact that he placed the rocks abo\-e the con- 

 glomerate in the Potsdam. The Saginaw deposits are now placed in the 

 Taconic. There accompany the article several sketches of the contacts 

 between the conglomerate and the underlying iron formation as tlie autlior 

 saw them in the Saginaw and Goodrich mines. 



WiNCUELL, Horace V. Historical sketch of the discovery of mineral deposits 

 in tbe Lake Superior region. Proceedings of the Lake Superior Mining Institute, 

 1893, pages 19-22. 



In this article Horace V. Wiuchell recounts, among other things, the 

 incidents leading to the discovery of the ore deposits of the Jackson, Cleve- 

 land, Republic, and other mines. 



