﻿4G6 
  Scientific 
  Intelligence. 
  

  

  of 
  the 
  region. 
  The 
  following 
  will 
  serve 
  as 
  a 
  brief 
  outline 
  of 
  its 
  

   geology: 
  the 
  intrusion 
  of 
  two 
  distinct 
  sheets 
  of 
  igneous 
  rock 
  

   into 
  sedimentary 
  beds 
  of 
  great 
  thickness, 
  representing 
  deposits 
  

   from 
  the 
  Archean 
  through 
  Cretaceous 
  times; 
  a 
  general 
  folding 
  of 
  

   the 
  region 
  and 
  severe 
  local 
  disturbances 
  in 
  the 
  vicinity 
  imme- 
  

   diately 
  south 
  of 
  the 
  city 
  of 
  Aspen, 
  due, 
  probably, 
  to 
  the 
  pushing 
  

   upward 
  of 
  a 
  deeply 
  buried 
  igneous 
  mass, 
  resulted 
  in 
  a 
  profound 
  

   and 
  complicated 
  series 
  of 
  faults. 
  The 
  lines 
  of 
  faulting 
  have 
  since 
  

   served 
  as 
  channels 
  along 
  which, 
  widespread 
  mineralization 
  and 
  

   chemical 
  changes 
  have 
  been 
  effected 
  by 
  mineralized 
  waters. 
  The 
  

   ores, 
  which 
  are 
  chiefly 
  sulphides 
  of 
  lead 
  and 
  zinc 
  carrying 
  silver 
  

   and 
  associated 
  with 
  a 
  gangue 
  of 
  barite, 
  quartz, 
  and 
  dolomite, 
  are 
  

   commonly 
  found 
  at 
  the 
  crossing 
  of 
  two 
  faults, 
  one 
  dipping 
  steeply, 
  

   the 
  other 
  nearly 
  horizontal 
  ; 
  and 
  the 
  theory 
  is 
  advanced 
  that, 
  

   ascending, 
  minei-al-bearing 
  solutions 
  in 
  one 
  channel 
  meeting 
  those 
  

   of 
  a 
  different 
  nature 
  in 
  another, 
  caused 
  a 
  precipitation 
  of 
  ores 
  at 
  

   the 
  contact. 
  Since 
  ore 
  deposition, 
  erosion 
  has 
  carried 
  off 
  the 
  

   overlying 
  strata 
  to 
  an 
  amount 
  estimated 
  at 
  15,000 
  ft. 
  and 
  exposed 
  

   the 
  ore-bearing 
  beds. 
  c. 
  h. 
  w. 
  

  

  2. 
  Iowa 
  Geological 
  Survey, 
  Vol. 
  IX. 
  Annual 
  Report, 
  1898, 
  

   with 
  accompanying 
  papers, 
  by 
  Samuel 
  Calvin 
  and 
  II. 
  F. 
  Baix, 
  

   pp. 
  11-572, 
  plates 
  i-xiii, 
  1899. 
  — 
  The 
  great 
  bulk 
  of 
  this 
  volume 
  is 
  

   devoted 
  to 
  tlie 
  elaboration 
  of 
  the 
  details 
  of 
  geology 
  by 
  counties. 
  

   Discussions 
  of 
  particular 
  interest 
  are 
  those 
  on 
  the 
  Pleistocene 
  dis- 
  

   tribution 
  and 
  loess, 
  as 
  found 
  in 
  Udden's 
  report 
  on 
  Muscatine 
  

   County, 
  and 
  in 
  Norton's 
  report 
  on 
  Scott 
  County, 
  and 
  in 
  Bain's 
  

   discussion 
  of 
  the 
  Pleistocene 
  in 
  Carroll 
  County. 
  Also 
  of 
  interest 
  

   are 
  Udden's 
  study 
  of 
  the 
  range 
  of 
  species 
  in 
  the 
  Devonian 
  beds 
  of 
  

   Muscatine 
  County; 
  and 
  Norton's 
  facts 
  on 
  the 
  contents 
  of 
  

   Devonian 
  faunas 
  in 
  Scott 
  County. 
  The 
  closing 
  paper 
  is 
  by 
  

   Mosnat 
  on 
  the 
  Artesian 
  wells 
  of 
  the 
  Belle 
  Plaine 
  area. 
  By 
  means 
  

   of 
  the 
  well 
  records 
  valuable 
  details 
  of 
  underground 
  structures 
  

   are 
  developed. 
  av. 
  

  

  3. 
  Geological 
  Survey 
  of 
  Michigan, 
  vol. 
  vi, 
  1893-1897. 
  L. 
  L. 
  

   Hubbard, 
  State 
  Geologist. 
  — 
  This 
  volume 
  consists 
  of 
  three 
  parts. 
  

   The 
  first 
  by 
  Dr. 
  A. 
  C. 
  Lane, 
  of 
  281 
  pp., 
  is 
  a 
  geological 
  report 
  on 
  

   Isle 
  Royale. 
  The 
  structure 
  of 
  the 
  island 
  is 
  thoroughly 
  described 
  

   and 
  discussed 
  with 
  special 
  reference 
  to 
  the 
  copper 
  mining 
  industry. 
  

   The 
  petrography 
  of 
  the 
  igneous 
  rocks 
  is 
  also 
  fully 
  entered 
  into. 
  

   In 
  the 
  same 
  thorough 
  way 
  Dr. 
  Hubbard 
  has 
  given 
  an 
  account 
  of 
  

   Keweenaw 
  Point 
  in 
  Part 
  II, 
  containing 
  155 
  pages. 
  These 
  reports 
  

   are 
  fully 
  illustrated 
  with 
  maps, 
  sections, 
  diagrams 
  and 
  photo- 
  

   graphs. 
  In 
  an 
  appendix 
  Dr. 
  Chas. 
  Pal 
  a 
  cue 
  gives 
  the 
  results 
  of 
  

   a 
  detailed 
  crystallographic 
  study 
  of 
  the 
  calcite 
  crystals 
  from 
  the 
  

   copper 
  mines 
  of 
  the 
  Lake 
  Superior 
  region, 
  so 
  long 
  celebrated 
  for 
  

   the 
  beauty 
  and 
  perfection 
  of 
  their 
  crystallization. 
  l. 
  v. 
  p. 
  

  

  4. 
  Report 
  on 
  Gypsum 
  and 
  Gypsum 
  Cement 
  Plasters 
  ; 
  by 
  G. 
  P. 
  

   Grimsley 
  and 
  E. 
  \\. 
  S. 
  Bailey, 
  under 
  the 
  direction 
  and 
  with 
  

   the 
  assistance 
  of 
  Erasmus 
  Haworth. 
  Vol. 
  V 
  of 
  the 
  University 
  

   Geological 
  Survey 
  of 
  Kansas; 
  pp. 
  183, 
  plates 
  xxx. 
  Topeka, 
  

  

  