﻿Geology 
  and 
  Natural 
  History. 
  259 
  

  

  The 
  notation 
  used 
  in 
  the 
  book 
  is 
  the 
  old 
  equivalent 
  notation 
  ; 
  which 
  

   seems 
  unfortunate 
  since 
  it 
  is 
  not 
  in 
  accord 
  with 
  that 
  based 
  on 
  the 
  

   atomic 
  theory 
  now 
  generally 
  employed. 
  The 
  great 
  advantage 
  of 
  

   considering 
  the 
  heat-changes 
  in 
  all 
  reactions, 
  and 
  the 
  evident 
  care 
  

   with 
  which 
  the 
  descriptive 
  part 
  has 
  been 
  written, 
  will 
  make 
  Pro- 
  

   fessor 
  Ditte's 
  book 
  acceptable 
  to 
  the 
  chemist. 
  We 
  shall 
  look 
  

   with 
  interest 
  for 
  the 
  remaining 
  parts. 
  g. 
  f. 
  b. 
  

  

  II. 
  Geology 
  and 
  Natural 
  History. 
  

  

  1. 
  Composition 
  of 
  the 
  Till 
  or 
  Bowlder-Clay 
  ; 
  by 
  W. 
  G. 
  

   Crosby 
  (Proc. 
  Bost. 
  Soc. 
  Nat. 
  Hist., 
  xxv, 
  1890). 
  — 
  In 
  this 
  paper 
  

   Professor 
  Crosby 
  gives 
  the 
  results 
  of 
  an 
  investigation 
  of 
  the 
  

   glacial 
  deposits 
  in 
  the 
  vicinity 
  of 
  Boston. 
  His 
  analyses 
  show 
  

   that 
  the 
  proportion 
  of 
  true 
  clay 
  in 
  the 
  till 
  is 
  small 
  and 
  that 
  of 
  

   rock-flour, 
  or 
  very 
  finely 
  pulverized 
  rock, 
  is 
  large. 
  He 
  concludes 
  

   that 
  the 
  proportion 
  of 
  stones 
  over 
  two 
  inches 
  in 
  diameter 
  is 
  not 
  

   over 
  5 
  to 
  10 
  per 
  cent. 
  His 
  results 
  give 
  for 
  the 
  gravel, 
  24-90 
  per 
  

   cent 
  ; 
  the 
  sand, 
  19 
  '51 
  ; 
  the 
  rock-flour, 
  43*86 
  ; 
  the 
  clay, 
  11*67 
  = 
  

   99*94. 
  In 
  his 
  table, 
  each 
  of 
  these 
  divisions 
  of 
  the 
  material, 
  is 
  

   farther 
  subdivided 
  into 
  coarse, 
  medium 
  and 
  fine. 
  Moreover, 
  he 
  

   gives 
  his 
  results 
  for 
  each 
  of 
  the 
  different 
  localities 
  studied. 
  In 
  

   the 
  redistribution 
  of 
  the 
  material 
  by 
  the 
  glacial 
  flood, 
  the 
  rock- 
  

   flour 
  goes 
  with 
  the 
  clay, 
  adding 
  to 
  its 
  volume, 
  so 
  that 
  the 
  clay- 
  

   beds 
  embrace 
  fully 
  half 
  of 
  *the 
  original 
  material 
  of 
  the 
  till. 
  The 
  

   rock-flour 
  was 
  found 
  to 
  be 
  essentially 
  quartz-flour 
  — 
  this 
  being 
  the 
  

   final 
  result 
  of 
  disintegration 
  and 
  the 
  consequent 
  decomposition 
  — 
  

   according 
  with 
  Daubree's 
  observation 
  that 
  the 
  milky 
  turbidity 
  

   of 
  the 
  Rhine, 
  even 
  for 
  hundreds 
  of 
  miles 
  from 
  the 
  Alpine 
  

   glaciers, 
  is 
  due 
  chiefly 
  to 
  impalpable 
  quartz.. 
  It 
  is 
  further 
  con- 
  

   cluded 
  that 
  of 
  the 
  material 
  of 
  the 
  till, 
  one-third 
  is 
  probably 
  of 
  

   preglacial 
  erosion, 
  and 
  two-thirds 
  of 
  glacial 
  erosion. 
  The 
  amount 
  

   of 
  rock-flour 
  is 
  evidence 
  in 
  favor 
  of 
  this. 
  But 
  the 
  fact 
  does 
  not, 
  

   Professor 
  Crosby 
  observes, 
  lend 
  support 
  to 
  the 
  view 
  that 
  the 
  

   glacier 
  " 
  profoundly 
  modified 
  the 
  topography 
  of 
  the 
  glaciated 
  

   area." 
  These 
  are 
  a 
  few 
  of 
  the 
  important 
  facts 
  and 
  conclusions 
  

   in 
  Professor 
  Crosby's 
  excellent 
  paper. 
  

  

  2. 
  Geology 
  of 
  the 
  Rocky 
  Mountain 
  Region 
  in 
  Canada 
  with 
  

   special 
  reference 
  to 
  changes 
  hi 
  Elevation 
  and 
  to 
  the 
  History 
  of 
  

   the 
  Glacial 
  Period 
  ; 
  by 
  Dr. 
  G. 
  M. 
  Dawson. 
  — 
  The 
  eighth 
  vol- 
  

   ume 
  of 
  the 
  Transactions 
  of 
  the 
  Royal 
  Society 
  of 
  Canada, 
  con- 
  

   tains, 
  among 
  its 
  papers, 
  the 
  very 
  valuable 
  Presidential 
  Address 
  

   of 
  Dr. 
  G. 
  M. 
  Dawson 
  on 
  the 
  above 
  subject. 
  The 
  Mesozoic 
  and 
  

   Tertiary 
  history 
  occupies 
  22 
  pages, 
  and 
  the 
  Glacial 
  history 
  the 
  

   following 
  50 
  pages. 
  

  

  3. 
  The 
  Greenstone 
  Schist 
  areas 
  of 
  the 
  Menominee 
  and 
  Mar- 
  

   quette 
  regions 
  of 
  3fichigan 
  ; 
  by 
  Professor 
  G. 
  H 
  Williams. 
  218 
  

   pp. 
  8vo, 
  with 
  plates 
  and 
  cuts. 
  Bulletin 
  IT. 
  S. 
  Geol. 
  Survey, 
  No. 
  

   62. 
  — 
  The 
  important 
  subject 
  here 
  discussed 
  ably 
  and 
  with 
  great 
  

   fulness, 
  by 
  the 
  author 
  is 
  — 
  the 
  Methods 
  in 
  which 
  a 
  massive 
  crys- 
  

  

  