INDEX. 



Vll 



Jjitbologists who have studied Lake Supe- 

 rior rocks, 74. 



Litholo^y, defects of ita metlioda, 74 ; of 

 iron district, 3, 7. 



Limestone, associated with serpentine, GG. 



Limonite, hotryoidal ore of Pcudill Mine, 

 51. 



Lingulic ill sandstone, 20. 



Lookc, J., on Presque Isle serpentine, 63; 

 metamorphie origin of Keweenaw Point 

 rocks, 79, 80 ; on quartz veins, 0. 



Logan, W. E., on the Caleifcrous and Pots- 

 dam ago of the copper-bearing rocks, 94 ; 

 Cambrian age of sandstone, 90 ; confusion 

 of Ai^oic with copper-bearing rocks, 91 ; 

 eastern sandstone of Cbazy age, 94 ; er- 

 roneous statement of Hougliton's views, 

 83 ; sandstone older than. Potsdam, 83. 



McCoMBEK Mine, minerals of, 51 ; geologi- 

 CJil structure of, 51. 



Maefarlaue, T., maintains the Permian age 

 of the Ijake Superior sandstone, 94 ; op- 

 poses Sclwyn's views, 106. 



Magnetite, octahedrons of, 30, 33 ; caught 

 up by a dike, 45 ; dikes of, 36 ; altered to 

 hematite, 39 ; network form of, 66 ; 

 produced in the alteration of olivine, 61 ; 

 surrounded by hematite fdnis, 48 ; rec- 

 tangular network of, 01; its relations to 

 marLite, 34, 35. 



Maine, trap of, 81. 



Malachite on Keweenaw Point, 70. 



Manganite at MeComber Mine, 51. 



Mareou,iJ., on the igneous origin of copper, 

 90 ; maintains the New Red age of the 

 Lake Superior sandstone, 90; copper 

 veins dike formations, 90. 



Margarophjllites in garnet, 53. 



Mai-quctle, dikes near, 36, 37, 38 ; sand- 

 stone of, 60. 



Marquette region, Laureutian and Huro- 

 nian in, 23 ; stratigraphy of, 19 ; iron ore 

 in, 6, 7 ; sediuentary roeka of, 74, 75. 



Masonite mieroscopieally like ottrelite, 45. 



Massaclmsctts, Eastern, geological methods 

 followed in, 73. 



Martite, relations to miagnctite, 34, 35 ; 

 octahedrons of, 33. 



Marvine, A. R., on the formation of the 

 copper-bearing veins, 103 ; on the con- 

 centration of the copper in the veins, 102 ; 

 his geological observations sustained, 131; 

 relation of trap and sandstone, 111 ; on 

 conglomerate beds, 100 ; origin of amyg- 

 daloid structure, 100, 101 ; sup])ort8 the 

 view^ of Foster and Whitney, 103 ; his 

 report on copper-benring rocks, 100-103 ; 

 on metaraorphism, 101, 102. 



Mclaphyr, an altered basalt. 111 ; dikes of, 

 at Coppper Falls Mine, 111, 113; fre- 

 quently mined on Keweenaw Point, 111 ; 

 glassy material formerly in, 135, 126 ; 

 impregnated with copper, 130; locally lim- 

 ited, 128; microscopic examination of, 

 from junction with jasper, 44 ; micro- 

 seopie study of, from Washington Mine, 

 43 ; pebbles of, replaced by copper, 126; 

 at Portage Lake, 94 ; relation of first lava 

 How to underlying sandstone, 114, 115; 

 richer in copper near a vein, 125. 



Menominee district, granite of, 24, 71; 

 iron ore in, 3, 6, 7 ; Laureutian in, 23 ; 

 Hurouiau rocks of, 23. 



Mctarnorphic rocks, origin of, 3, 5, 6, 7, 8, 

 9, 10, 11, 14, 15. 



Metamorphism, the agent of, 35; of crystal- 

 line rocks, 8, 9, 14, 15 ; exciting cause 

 of^ 27; of traps and sandstones, 101, 103; 

 of schists, 36. 



Mica, in argillaceous sandstone, 116; sec- 

 ondary origin of, 38; greenish, in quartz 

 1*0 ck, 49. 



Michigan geologists, defective methods of, 

 118. 



Mierocline in granite, 67. 



Mierolites, of apatite, 37 ; in feldspar and 

 quartz, 56 ; in quartz, 38, 44. 



Microscope, use of, in the study of rocks, 73, 



74. 



Microscopic analysis, insufficient to prove 



origin of rock, 43. 

 Microscopic distinction between lava flows 



and intrusive rocks, 111, 

 Microscopic examination of Lake Angeline 



diorite, 42. 

 Mineral Point Railroad, microscopic study 



of pebbles from, 120. 

 Mining, destructive of geological evidence, 



68. 

 Montalhan series in the iron region, 24. 

 Mud -flows in shale, 131. 

 Miiller, A., copper reduced by organic mat- 

 ter and oxide of iron, 93. 

 Murray, A., Huronian age of iron district, 



13. 

 Muscovite, cutting biotito, 56; folia of, in 



feldspar, 57; in feldspar, 56. 



Negaunee, Michigan, ernptive diorite at, 

 41 ; "soft hematite" mines of, 51. 



Nevadite, 72. 



New England, methods of observation in, 73. 



New Jersey, sandstone of, contemporaneous 

 with that of Keweenaw Point, 79. 



New Red sandstone of tipper SiluriaP^ age, 

 89, 90. 



New York Mine, quartzite of, 59. 



