INDEX. 



lU 



Copper district, history of geological views in 



regard to, 76-107. 

 Copper Falls Mine, ash-bed of, 125 ; best 



veinstone at, 130 ; character of copper 



deposits mined, 129 ; copper spikes at, 



126 ; Owl Crecic, vein of, 129 ; relation 



of traps and sandstone at, 110-113 ; 



proofs of water action at, 123, 120. 

 Copper Harbor, rocks of, 80. 

 Copper pyrites, reported abundant in the 



iron district, 4. 

 Copper veins, origin of, 79, 80, 82, 84, 85, 



88, 89, 90, 9i; 92, 103, 106, 107, 108, 



109. 

 Cordilleras, rhyolites of, 118, 119 ; volcanic 



rocks of, 48. 

 Credner, II., dikes near Mar^ette, 36 ; on the 



geology of the iron district, 17; on the 



original condition of the iron ore, 32. 

 Crosby, W. O., iron ores and jasper a "red 



clay " deep-sea deposit, 25. 

 Cumming, J. G., glacial action in early 



geological ages, 85. 



D.-i.DDOW, S. H., volcanic origin of iron ore, 

 16, 17. 



Dana, J. D., copper in contact deposits, 127 ; 

 on the formation of veins and the altera- 

 tion of rocks, 106, 107 ; on the origin of 

 copper deposits, 89, 93, 94 ; on the origin 

 of the iron ore, 13 ; Potsdam and Calcif- 

 erous age of the sandstone, 93 ; his theory 

 of the copper deposits not based on facts, 

 131 ; Triassic age of the sandstone, 93 ; on 

 the union of copper and silver, 105, 106. 



Davies, D. C, errors in his work on " Met- 

 alliferous Minerals and Mining," 25, 26. 



Dawson, J. W., his theory of the deposition 

 of the copper, 92, 93. 



Dead River, granite of, 56. 



Deer Lake, diorite of, 42, 43. 



Detrital deposits of iron ore and jasper, 30, 

 31. 



Devitrification, in rhyolites and felsites, 33. 



Diabase, alteration form of, 46 ; an altered 

 basalt, 111; decomposition of, 43; erup- 

 tive in Eastern Massachusetts, 72 ; micro- 

 scopic study of that of various localities, 

 39, 40, 42, 45 ; not mined on Keweenaw 

 Point, 111 ; an old crystalline basalt, 39. 



Diallage, in peridotitc, 60, 61. 



Dike, at Old Washington Mine, variations 

 in structure of, 48 ; step form of, at Salis- 

 bury iline, 42. 



Dikes, near Marquette, microscopic study of, 

 36, 37 ; of iron ore and jasper, 30, 31, 

 32 ; of magnetite, 36 ; of schist, 48. 



Diller, J. S., on the eruptive origin of felsite, 

 72. 



Diorite, alteration products in, 36, 37 ; con- 

 taining fragments of rocks, 39 ; enipted 

 later than the jasper and ore, 51, 52 ; 

 eruptive origin of, 17, 26, 46; eruptive 

 through schist, 41 ; foliation of eruptive, 

 47 ; garnet-bearing, of Republic Mountain, 

 47 ; hill of, between Salisbury and Lake 

 Angeline Mine, 49, 50 ; interstratified 

 eruptive, 23 ; interstratified with schists, 

 14, 15, 17, 19, 20, 26 ; intrusive at Light- 

 house Point and Picnic Island, 23 ; and 

 at Republic Mountain, 47 ; microscopic 

 examination of, from various localities, 39, 

 41, 42, 44, 45, 46, 47; mineralogically 

 like the schist, 37 ; of Marquette district 

 and the traps of Keweenaw Point the 

 same, 12 ; passage into schist, 40 ; relation 

 to jasper and iron ore, 51, 52 ; resem- 

 bling chlorite schist, 42 ; resembling horn- 

 blende schist, 45 ; sedimentary origin of, 

 advocated by various writers, 14, 17, 18, 

 19, 20, 25, 26, 40; younger than the 

 Huronian, 17 ; secondary origin of min- 

 erals in, 46. 



Dolomite, of Presque Isle, 2, 3, 10, 23 ; sec- 

 ondary origin of, in peridotitc, 61, 62, 64, 

 65 ; stratified, of Rominger, 61 ; veins of, 

 64. 



Douglass Houshton Fall, geological struc- 

 ture at, 95, 96, 115, 116. 



Drift agencies, in earlier geological times, 85. 



Eagle River Mixe, H. D. Rogers on, 



82, 83. 

 Eclogite, microscopic study of, from Old 



Washington Mine, 48. 

 Edwards Mine, eruptive character of iron 



ore, 35. 

 Emerson Adit, at Copper Falls Mine, 110, 



111. 

 Enstatitc, alteration of, 61 ; in peridotite, 



60, 61. 

 Eozoon Canadense, alteration structure re- 

 sembling, 114. 

 Epidote, in Republic Mountain granite, 54 ; 



secondary origin of, 37, 42, 56, 120. 

 Epidote veins, relation of, 84. 



F.iULT, on eastern side of Presque Isle, 64. 



Feldspar, alteration of, 39, 42 ; decomposi- 

 tion of, 38, 114, 117, 119, 120 ; decompo- 

 sition products in, 55,56 ; inclusions in, 36 ; 

 inclusions of base in, 37, 44 ; replaced by 

 kaolin, 43 ; secondary origin of, 113, 114, 

 119; stone inclusions in, 42 ; unstriated 

 form sometimes due to alteration, 55. 



Felsite, alteration of, 38 ; dikes of, 38, 39 ; 

 eruptive characters of, 38 ; fluidal struc- 

 ture in, 38 ; intrusive, of Eastern Massa- 



