﻿Geology 
  and 
  Mineralogy. 
  73 
  

  

  Fe 
  2 
  3 
  , 
  AloOs 
  

  

  Mn0. 
  2 
  

  

  MgC0 
  3 
  

  

  Organic 
  matter 
  

  

  Gangue 
  

  

  1. 
  11-2 
  

  

  24-7 
  

  

  2-0 
  

  

  12-0 
  

  

  496 
  = 
  99-5 
  

  

  2. 
  87 
  

  

  250 
  

  

  2-6 
  

  

  12 
  8 
  

  

  502 
  = 
  99-3 
  

  

  3. 
  14-0 
  

  

  406 
  

  

  31 
  

  

  10-0 
  

  

  321 
  = 
  99'8 
  

  

  11. 
  A 
  Treatise 
  on 
  Crystallography 
  ; 
  by 
  W. 
  J. 
  Lewis, 
  Professor 
  

   of 
  Mineralogy 
  iu 
  the 
  University 
  of 
  Cambridge. 
  8vo, 
  pp. 
  1-612, 
  

   Cambridge, 
  1899 
  (The 
  University 
  Press). 
  — 
  So 
  many 
  of 
  the 
  trea- 
  

   tises 
  on 
  crystallography 
  form 
  merely 
  a 
  part 
  of 
  mineralogical 
  text- 
  

   books, 
  and 
  hence 
  are 
  limited 
  to 
  the 
  every-day 
  requirements 
  of 
  

   elementary 
  students, 
  that 
  the 
  breadth 
  of 
  the 
  subject 
  might 
  be 
  

   overlooked, 
  were 
  it 
  not 
  for 
  the 
  occasional 
  appearance 
  of 
  a 
  thor- 
  

   ough 
  and 
  exhaustive 
  work. 
  Such 
  an 
  one 
  was 
  presented 
  some 
  

   years 
  ago 
  by 
  Professor 
  Story-Maskelyne, 
  and 
  we 
  now 
  have 
  

   another 
  from 
  the 
  hand 
  of 
  Professor 
  Lewis, 
  of 
  Cambridge. 
  

  

  Students 
  of 
  the 
  subject 
  not 
  content 
  with 
  gaining 
  merely 
  such 
  

   knowledge 
  as 
  is 
  necessary 
  to 
  enable 
  them 
  to 
  handle 
  ordinary 
  

   crystals, 
  will 
  find 
  much 
  to 
  interest 
  them 
  and 
  require 
  their 
  study 
  

   in 
  this 
  able 
  and 
  profound 
  discussion. 
  The 
  theoretical 
  relations 
  of 
  

   rational 
  indices, 
  zone 
  laws, 
  symmetry, 
  and 
  so 
  on, 
  are 
  presented 
  

   with 
  great 
  minuteness, 
  and 
  then 
  the 
  different 
  classes 
  under 
  the 
  

   successive 
  systems 
  are 
  taken 
  up 
  in 
  succession 
  commencing 
  with 
  

   the 
  anorthic 
  system 
  (triclinic). 
  These 
  classes 
  are 
  named 
  in 
  part 
  

   in 
  a 
  manner 
  analogous 
  to 
  that 
  of 
  Groth, 
  and 
  in 
  part 
  entirely 
  new 
  

   terms 
  are 
  introduced. 
  For 
  example, 
  under 
  the 
  oblique 
  (mono- 
  

   clinic) 
  system, 
  the 
  gonioid 
  class 
  corresponds 
  to 
  the 
  domatic 
  class 
  

   of 
  Groth 
  (clinohedral 
  group) 
  and 
  the 
  plinthoid 
  to 
  his 
  prismatic 
  

   class 
  (normal 
  or 
  holohedral 
  group). 
  A 
  chapter 
  of 
  one 
  hundred 
  

   pages 
  is 
  devoted 
  to 
  a 
  thorough 
  discussion 
  of 
  twin 
  crystals, 
  first 
  

   considered 
  in 
  general, 
  and 
  then 
  with 
  respect 
  to 
  occurring 
  forms 
  

   under 
  the 
  different 
  systems. 
  Another 
  chapter 
  takes 
  up 
  analytical 
  

   methods, 
  with 
  a 
  brief 
  classification 
  of 
  other 
  systems 
  of 
  notation 
  

   than 
  that 
  of 
  Miller, 
  here 
  followed 
  ; 
  and 
  the 
  work 
  closes 
  with 
  

   an 
  account 
  of 
  diflerent 
  forms 
  of 
  goniometers. 
  

  

  12. 
  Praktische 
  Anleitung 
  zur 
  Analyse 
  der 
  Silikatgesteine 
  nach 
  

   den 
  methoden 
  der 
  Geologischen 
  Landesanstalt 
  der 
  Vereinigten 
  

   Staaten 
  von 
  Dr. 
  W. 
  F. 
  Hillebraxd. 
  Nebst 
  einer 
  Einleitung 
  

   enthaltend 
  einige 
  Prinzipien 
  der 
  petrographisch-chemischen 
  

   Forschung 
  von 
  F. 
  W. 
  Clarke 
  und 
  W. 
  F. 
  Hillebrand. 
  Ueber- 
  

   setzt 
  von 
  Dr. 
  E. 
  Zschimmer; 
  pp. 
  86. 
  Leipzig, 
  1899 
  (W. 
  Engel- 
  

   mann.) 
  — 
  This 
  useful 
  volume 
  is 
  essentially 
  a 
  German 
  reproduction, 
  

   with 
  some 
  changes 
  chiefly 
  of 
  arrangement, 
  of 
  the 
  general 
  portion 
  

   of 
  Bulletin 
  No. 
  148 
  (1897) 
  of 
  the 
  U. 
  S. 
  Geological 
  Survey. 
  The 
  

   excellent 
  analytical 
  work 
  carried 
  on 
  in 
  the 
  laboratory 
  of 
  the 
  

   Survey 
  under 
  the 
  charge 
  of 
  Prof. 
  Clarke, 
  largely 
  by 
  Dr. 
  W. 
  P. 
  

   Hillebrand, 
  has 
  contributed 
  much 
  to 
  our 
  knowledge 
  not 
  only 
  of 
  

   the 
  composition 
  of 
  minerals 
  and 
  rocks, 
  but 
  also 
  of 
  the 
  best 
  

   methods 
  of 
  analysis. 
  It 
  is 
  gratifying, 
  therefore, 
  that 
  this 
  excel- 
  

   lent 
  treatise 
  should 
  be 
  put 
  in 
  a 
  form 
  to 
  command 
  a 
  still 
  wider 
  

   circle 
  of 
  readers. 
  

  

  1 
  3. 
  Darstellung 
  der 
  32 
  moglichen 
  Krystallklassen 
  auf 
  Grundder 
  

   Deck- 
  und 
  Spiegelachsen 
  nebst 
  Beschreibung 
  von 
  Achsenmodellen 
  

  

  