﻿Geology. 
  573 
  

  

  5 
  Switzerland, 
  Germany, 
  Austro-Hungary, 
  and 
  southern 
  

  

  Russia. 
  

  

  6 
  Italy 
  and 
  West 
  Mediterranean 
  islands. 
  

   1 
  Balkan 
  Plateau, 
  Greece, 
  Aegean 
  isles. 
  

   8 
  Asia 
  Minor, 
  Persia, 
  Arabia. 
  

  

  The 
  last 
  grouping 
  is 
  taken 
  as 
  a 
  matter 
  of 
  convenience. 
  

  

  In 
  each 
  group 
  the 
  chief 
  occurrences 
  of 
  the 
  rocks 
  are 
  briefly 
  

   described, 
  with 
  remarks 
  directing 
  attention 
  to 
  their 
  salient 
  

   features, 
  while 
  frequent 
  tables 
  of 
  analyses 
  add 
  greatly 
  to 
  the 
  

   value 
  of 
  the 
  presentation. 
  The 
  labor 
  of 
  digesting 
  the 
  colossal 
  

   mass 
  of 
  literature 
  necessary 
  for 
  this 
  work 
  must 
  have 
  been 
  im- 
  

   mense, 
  and 
  some 
  idea 
  of 
  it 
  may 
  be 
  gained 
  from 
  the 
  comprehen- 
  

   sive 
  bibliography 
  submitted 
  in 
  the 
  final 
  pages. 
  This 
  geographical 
  

   conspectus 
  is 
  a 
  lasting 
  benefit 
  to 
  working 
  petrographers 
  in 
  ena- 
  

   bling 
  them 
  to 
  easily 
  compare 
  material 
  with 
  that 
  already 
  described 
  

   in 
  the 
  chief 
  publications 
  upon 
  all 
  parts 
  of 
  the 
  world. 
  In 
  addition 
  

   the 
  general 
  resumes 
  of 
  the 
  different 
  provinces 
  will 
  be 
  of 
  value 
  in 
  

   directing 
  attention 
  to 
  their 
  chief 
  peculiarities. 
  The 
  wide 
  travels 
  

   of 
  Professor 
  Iddings 
  and 
  his 
  personal 
  acquaintance 
  with 
  the 
  rocks 
  

   of 
  many 
  regions 
  give 
  an 
  additional 
  authority 
  to 
  this 
  portion 
  of 
  

   the 
  work. 
  

  

  On 
  the 
  whole 
  it 
  may 
  be 
  said 
  that 
  the 
  completion 
  of 
  this 
  great 
  

   work 
  marks 
  a 
  distinct 
  step 
  forward 
  in 
  the 
  science 
  of 
  petrology, 
  in 
  

   that 
  it 
  is 
  the 
  most 
  comprehensive 
  and 
  fundamental 
  treatment 
  of 
  

   the 
  subject 
  which 
  has 
  yet 
  appeared, 
  in 
  which 
  also 
  the 
  bearing 
  of 
  

   the 
  most 
  recent 
  advances 
  in 
  related 
  sciences 
  have 
  been 
  considered. 
  

   The 
  amended 
  qualitative 
  classification 
  proposed 
  seems 
  the 
  most 
  

   reasonable 
  way 
  out 
  of 
  this 
  vexed 
  problem, 
  in 
  combining 
  our 
  heri- 
  

   tage 
  from 
  the 
  past 
  with 
  the 
  greater 
  precision 
  demanded 
  from 
  

   present-day 
  workers 
  in 
  science 
  and 
  in 
  indicating 
  the 
  path 
  along 
  

   which 
  improvement 
  may 
  be 
  made 
  in 
  the 
  future. 
  It 
  is 
  perhaps 
  

   needless 
  to 
  say 
  that 
  the 
  volume 
  is 
  a 
  necessity 
  for 
  every 
  worker 
  in 
  

   the 
  science. 
  It 
  is 
  well 
  and 
  attractively 
  printed 
  and 
  both 
  author 
  

   and 
  publisher 
  are 
  to 
  be 
  congratulated 
  on 
  its 
  appearance. 
  

  

  l. 
  v. 
  P. 
  

  

  8. 
  Introduction 
  to 
  the 
  Study 
  of 
  Igneous 
  Rocks 
  • 
  by 
  Geo. 
  I. 
  

   Finlay. 
  12°, 
  pp. 
  228, 
  59 
  figs., 
  3 
  col. 
  pis. 
  New 
  York, 
  1913 
  

   (McGraw-Hill 
  Co.). 
  — 
  The 
  object 
  of 
  this 
  little 
  work 
  is 
  clearly 
  

   indicated 
  in 
  the 
  title. 
  The 
  author 
  first 
  discusses 
  the 
  classifica- 
  

   tion 
  of 
  rocks 
  from 
  the 
  generally 
  used 
  qualitative 
  method 
  and 
  

   then 
  takes 
  up 
  their 
  determination 
  in 
  hand 
  specimens. 
  This 
  is 
  

   followed 
  by 
  a 
  brief 
  discussion 
  of 
  the 
  movement 
  of 
  light 
  in 
  crys- 
  

   tals 
  and 
  the 
  identification 
  of 
  the 
  essential 
  rock 
  minerals 
  in 
  sec- 
  

   tions 
  by 
  optical 
  methods. 
  A 
  brief 
  description 
  of 
  the 
  accessory 
  

   minerals 
  is 
  given 
  and 
  the 
  most 
  important 
  varieties 
  of 
  the 
  igneous 
  

   rocks 
  are 
  then 
  presented. 
  Less 
  important 
  types 
  are 
  mentioned 
  in 
  

   tabular 
  form. 
  After 
  giving 
  the 
  proper 
  method 
  for 
  describing 
  

   rocks 
  the 
  work 
  closes 
  with 
  a 
  rather 
  full 
  account 
  of 
  the 
  Quantita- 
  

   tive 
  System 
  of 
  Classification. 
  Examples 
  for 
  the 
  calculation 
  of 
  

   the 
  norm 
  are 
  discussed 
  and 
  the 
  necessary 
  numerical 
  tables 
  are 
  

  

  Am. 
  Jour. 
  Sci. 
  — 
  Fourth 
  Series, 
  Vol. 
  XXXVI, 
  No. 
  215. 
  — 
  November, 
  1913, 
  

  

  38 
  

  

  