GEOLO(iIC'AL EXl'L()UAJ'lO>;s AM) LITEUATITRE. 8*7 



groups fallinjj- witliin the s:iiut' iiit«Tv;il in other ivo-joiiK. 'l^) coNer this 

 general g-eologicai interval, naiiiclv, that Iving between the ( 'amhriau and 

 the basement crystallines, to whicli it is proposed that the term Archean 

 should be restricted, tlie jjaper aihocates the use of the new name 

 Af/iKito^dic, of equal rank with J'nli'o-nic, Mcs(iziih\ etc 



HrRKiNBiNE (John). The Inm Ores East of the Mississippi River. U. S. 

 Ge()logieal Sarvej', J. W. Powell, Director. Mineral Resoni'ces of tlie United States 

 for 1886, David T. Day, Chief of Division of Mining Statistics and Technology, pp. 

 39-10.3. 



Mr. John Birkinbine contributes the article upon "Tlic Iron ( )res East 

 of the Mississippi River" for this volume. In it lie gives cpiite a full and 

 accurate account of the development of the Gogel)ic range, from which the 

 following somewhat extended extracts are made (pp. G7— 72): 



III order of iiiiportaiice as shipjiers the various districts coiniirisiiig the lake 

 Sn))erior region ranked in ISSfias follows: (1) Marcpiette; (2) Menominee: (.'>) (iogebic; 

 (4) \'ermilion; and this order will he maintained in 1S<S7, with tlie possibility of the 

 Gogebic aud Menoiuinee ranges chiuiging places, but it is jirobable that these two 

 districts will not vary greatly in their ontpiits for 1S,S7. 



(ieograpliically the (Iogebic iron range may be described as running nearly 

 parallel with the .southern shore of lake Sujierior, and about l."i miles distant from it; 

 The Montreal river (which is the boundary l)etweeii the State of Wiscuaisin and the 

 upper yieninsnla of .Michigan), flowing northward into the lake, cuts through the 

 range nearly midway between the extn'Uies of the jiresent exploitations, about one- 

 half of the ore strike, as now believed to be determined, lying in Ontonagon county, 

 Michigan, and the other half in Ashland county, Wisconsin. 



The o(!(rurrence of ores similar in character to those of the (iogebic iron laiigc in 

 lenses or pockets in the Marquette aud Menominee ranges naturally ])oiiits to lilic 

 deposits in this newer district, and there .seems good reason to beliinc that the ores 

 lie in lenses of greater or less width and dciitli throughout an ore-bearing stratuin 

 confined by the quartzite liaiigiug wall of what is believed to be the north vein, and 

 the foot wall of ■what is usually known as the sontli vein, with a greater probability of 

 finding the ore in this newer region, owing to the aiijiarent iiersistence and regularity 

 of the foot wall. Tjocal o]>inions favor, however, and not withont reason, the existence 

 of two veins, although the pie.sence of two apparently di.stinct ore bodies is .shown, so 

 far, in but few instances. The belief in the existence of two veins is baseii npon their 

 positions relative to the foot wall, and also to a greater percentage of manganese in 

 the south vein. 



