INDEX. 



[Bull. Mus. Conip. Zool., Geol. Series I. No. 1.] 



ACTIXOLITE, joining quartz grains, 54 ; 

 needles of, in garnet, 47 ; secondary ori- 

 gin of, 39, 47. 



Actinolite rock, contact with granite, 53. 



Actinolite schist, relation to the iron ore, 35. 



Agassiz, A., Eastern sandstone deposited 

 later than the trap, 96 ; geological stnir- 

 ture at Douglass Houghton Falls, 115; 

 mistakes the views of Foster and Whit- 

 ney, 96; rehition of sandstone and trap 

 near Torch Lake, 95, 96. 



Agassiz, L., on the orisjin of copper deposits, 

 88, 89. 



Alteration products in plagioclasc, 56. 



Amygdaloid at base of traps, 81 ; defined, 

 128 ; deposited by water, 94 ; presence on 

 Keweenaw Point denied by Bayfield, 77. 



.\mygdaloidal structure, orisin of, 78, 81, 

 84, 86, 87, 88, 100, 101,123, 129. 



.\raygdules, composition of, 180. 



Analcime, igneous origin of, 80. 



Andesite, probable occurrence ol', 37, 38. 



Apatite, in an old trachyte, 12(T; in gneiss, 

 57; niicrolites of, 37. 



Argillaceous detritus, alteration and crystal- 

 lization of, 58. 



Argillite, 28 ; south of ^Marquette, 37. 



Asbestus, ehiTSotile mistaken for, 66. 



Ash-bed, confounded with detrital deposits, 

 112, 113; copper deposits in, 125; how 

 formed, 91, 112: poor in copper near 

 veins, 125 ; structure of, 125 ; tonsrues 

 of, in trap, 113 ; tongues of trap in, 125. 



Atlantic Mine, character of copper deposit 

 at, 129; supposed "ash-bed" of, 125; 

 thermal water action at, 125, 126. 



Augite, alteration to hornblende, 37, 46 : 

 dtered to hornblende and chlorite, 39 ; 

 altered to hornblende and viridite, 42 : al- 

 tered to viridite, 37; cut by feldspar 

 crystals, 37, 42 ; formina: cores in horn- 

 blende, 37. 



Australia, origin of placer gold of, 17. 



Azoic age of iron region, 20. 



Azoic system, defined, 7, 8, 9 ; first proposed 

 by Foster and Whitney, 7 ; its relation to 



the Silurian system, 9 ; lithological char- 

 acters of the, 8, 9. 



Baco.v, D. H., 131. 



Banding, no proof of stratification, 28. 



Bannan, Benjamin, volcanic origin of iroa 

 ore, 16. 



Barite at McComber Mine, 51. 



Basalt, alteration of, 70. 



Basaltic rocks, alteration of, 105. 



Base, alteration of, 37, 40, 44 ; alteration 

 products taken for, 44 ; forming stone 

 cavities, 42 ; globulitic form of, 40 ; 

 unaltered globulitic, 44. 



Bauermann, II., derivation of copper from 

 the sandstone, 127 ; origin and sequence 

 of minerals 95 ; on the deposition of the 

 copper, 94, 95. 



Bayfield, H. W., granite and trap of Kewee- 

 naw Point older than sandstone, 77 ; " Old 

 Red " age of sandstone, 77- 



Beaches, sea, in iron district, 31. 



Bell, Robert, copper-bearing rocks of Per- 

 mian or Triassic age, 97. 



Bete Grise Bay, dip of sandstone at, 88. 



Bibliography of the Geology of Lake Supe- 

 rior, 133-157. 



Bigsby, .1. J., Cambrian age of sandstone, 

 90 ; sandstone of " Old Red " age, 77. 



Biotite, alteration product of hornblende, 

 56 ; connecting quartz grains, 54 ; cut 

 by muscovite, 56 ; in granite, derived 

 from schist, 54 ; secondary origin of, 36, 

 42, 46, 47. 



Bohemian Mountains, origin of, 86. 



Bolton, G. D., 132. 



Braintrce, ^lassachusetts, slates of, 72. 



Breccia, overlying iron ore, 30. 



Brooks, T. B., assumption that foliation and 

 stratification are coincident, 25 ; bedded 

 character of the iron ore, 18, 19 ; conclu- 

 sions based on lithological characters, 24 ; 

 coppor-bcaring rocks conformable with 

 Hnronian. 99, 100; evades the conclu- 

 sions logically resulting from his own 

 work, 24; formation x.t. of, 71, 72; 



