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X 



INDEX. 



Sandstone of Keweenaw Point, age of, 108 ; 

 belongs to the Quebec group, 93, 97 ; 

 Calciferous age of, 93, 94 ; Cambrian age 

 of, 90 ; cause of absence of fossils in, 85 ; 

 of Cbazy age, 94; of "New Red" age, 

 79, 80, 81, 89, 90, 93, 97 ; of "Old lied" 

 age, 77, 80; origin of, 82; of Permian 

 age, 94; of Potsdam age, 82, 91, 93, 

 103, 104, 107 ; pre-Potsdam age of, 83. 



Sandstone, Western, of same age as the 

 traps, 121, 122. ^^ 



Scbist, composed of basaltic detritus, 37 ; 

 contortion of stratification planes of, 07 ; 

 garnet -bearing, of Republic Mountain, 47 ; 

 granite intrusive in, 55; Iluronian age 

 of, 14, 24, 52 ; lamination cut by iron 

 ore, 31 ; microscopic study of, 36, 37, 47, 

 48, 53, 58 ; mineralogically like diorite, 

 37 ; passage of magncsian, into dioritic 

 rocks, 20 ; its relation to tbe iron ore, 31 ; 

 sedimentary origin of, 20, 48; uplifted 

 by granite, 53 ; welded to granite, 53. 



Schoolcraft, H. R., falsilieation of original 



documents in his " Summaiy Narrative" 



of 1854, 10, 11; bis views in regard 



' to the copper region of Lake Superior, 



70. 

 Schoolbouse Mine, conglomerate at, 30 ; 



dike of jasper at, 30. 

 Sedimentary origin of eruptive and crystal- 

 line rocks, 11, 12, 14, 15; of the iron 



ore, G, 14, 15. 

 Sedimentary rocks, rapid deposition of, 118. 



Selwyn, A. R. C, on the Hnronian age of 

 the copper-bearing rocks, 100. 



Serpentine, an alteration form of peridotite, 

 61, 66; an alteration product of olivine, 

 42; on the formation of, 75 ; microscopic 

 study of, from Isbpeming, 05, 60 ; net- 

 work structure of, 01 ; origin of, 64, 65 ; 

 of Presqiie Isle, 60-05. 



Shale, raindrop impressions, ripple-marks, 



and mud-flows in, 121. 

 Shelden and Coliimbinn Mine, character of 



copper deposit at, 1 29. 

 Silica, eruptive with hematite, 33. 

 Silver, its union with copper, 79, 81, 105, 



100, 109. 

 Spherulitic structure, produced by alteration, 



113. 119, 120. 

 Stone cavities in feldspar, 42 ; formed from 



devitrified base, 42; in quartz, 50. 

 Sweet, K. T., unconformability of Lauren- 



tian and Iluronian, 24. 



Tachylite, altered form of, 44. 

 Tale, in ottrclite schist, 45. 

 Teal Lake, diorite of, 41 ; limiination 

 schist at, 41 ; quartzite of, 9, 



of 



Thermal waters, action of, 49, 50, 51, 116, 

 117, 123, 124, 125, 126. 



Titanite, in granite, 56. 



Torch Lake, sandstone quarry at, 117. 



Tourmaline, in cclogite, 48 ; crystals in 

 diorite, 45 ; in ottrclite schist, 45 ; pres- 

 ence of, in iron region, 75 ; in radiating 

 groups of crystals in quartz, 45. 



Trachyte, microscopic study of, 113, 114, 

 117, 120; pebbles of, 113. 



Trap, action on the sandstone, 86-88, 101- 

 103 ; age relative to Eastern sandstone, 

 108 ; amygdaloidai and scoriaceous on 

 upper surfa(;e, 110; characters and rela- 

 tions of, 104,109-113, 118, 128; denu- 

 dation of, before sandstone was deposited, 

 113 ; evidence that they are lava flows, 

 127, 128 ; pseudo-stratification of, 86 ; 

 sends tongues into the "ash-bed," 113; 

 tongues of, extending into sandstone, 

 110; metamorphie sedimentary origin 



of, 91. 



Triassie age of copper -bearing rocks, 97. 



Triehites in quartz, 59, 120. 



UNCONFGUMARTLiTy, based on foliation and 

 lamination, 71 ; not proof of distir.ct age, 

 31. 



Vapor cavities in quartz, 39. 



Veins, filling of, 124, 129; of iron ore, 29; 



variations of, 129 ; width of, 124. 

 Veins fissure, formation of, on Keweenaw 



Point, 123. 

 Vein material, derived from the traps, 123. 

 Veinstones, character of best forms, 130. 

 Viridite, replacing augite, 42 ; replacing 



base, 37. 

 Volcanic a(!tion, earlier than Tertiary times, 

 119 ; gradual increase and diminution of, 



122. 

 Volcanic origin of the copper-bearing rocks, 

 where shown, 131 ; of copper veins, 80. 



Warwick, Rhode Island, masunile of, 45. 



Washington Mine, rocks of, 43, 44, 45. 



Washington Mine (new), dikes of ore at, 36. 



Washington Mine (old), relations of iron 

 ore and actinolitc schist, 35. 



Water, action of percolating, 123, 129. 



Whitney, J. B., alternations in formation of 

 zeolites, 95 ; chemical analysis of Presque 

 Isle serpentine, 14, 62, 65; "Metallic 

 Wealth of the United States," 90 ; igneous 

 origin of iron ore, 1, 10; on the iron dis- 

 trict, 7. 



Whittlesey, C, copper-bearing rock contin- 

 uous with, but below, the sandstone, 94 ; 

 eruptive origin of granite, 24; Huroniau 



