﻿572 
  Scientific 
  Intelligence. 
  

  

  The 
  book 
  opens 
  with 
  a 
  discussion 
  of 
  the 
  scope 
  and 
  method 
  of 
  

   description, 
  in 
  which, 
  after 
  the 
  serial 
  nature 
  of 
  the 
  objects 
  to 
  be 
  

   considered 
  is 
  brought 
  out 
  by 
  the 
  use 
  of 
  tables 
  containing 
  in 
  

   graphic 
  form 
  the 
  results' 
  of 
  a 
  vast 
  mass 
  of 
  chemical 
  data, 
  the 
  

   urgent 
  need 
  of 
  quantitative 
  methods 
  in 
  classification 
  is 
  demon- 
  

   strated. 
  The 
  author 
  then 
  proposes 
  a 
  system 
  in 
  which 
  the 
  present 
  

   ill-defined 
  qualitative 
  one, 
  so 
  generally 
  used, 
  is 
  brought 
  into 
  

   more 
  definite 
  form 
  by 
  the 
  injection 
  into 
  it 
  of 
  a 
  certain 
  amount 
  of 
  

   quantitative 
  method, 
  thus 
  correlating 
  it 
  in 
  broad 
  features 
  with 
  

   the 
  quantitative 
  system, 
  as 
  already 
  forecast 
  in 
  volume 
  I, 
  pp. 
  348- 
  

   350. 
  The 
  rocks 
  are 
  thus 
  divided 
  into 
  six 
  divisions, 
  as 
  follows 
  : 
  

  

  I, 
  

  

  characterized 
  

  

  by 
  quartz. 
  

  

  II 
  

  

  a 
  

  

  " 
  quartz 
  and 
  feldspar. 
  

  

  II 
  [ 
  

  

  a 
  

  

  " 
  feldspar. 
  

  

  IV 
  

  

  a 
  

  

  " 
  feldspar 
  and 
  feldspathoids, 
  

  

  V 
  

  

  a 
  

  

  " 
  feldspathoids. 
  

  

  VI 
  

  

  u 
  

  

  u 
  mafic 
  minerals. 
  

  

  The 
  f 
  eld 
  spathic 
  rocks 
  are 
  again 
  divided 
  according 
  to 
  the 
  alkalic 
  

   or 
  alkalicalcic 
  nature 
  of 
  the 
  feldspars, 
  and 
  further 
  divisioning 
  

   according 
  to 
  the 
  relative 
  proportions 
  of 
  feldspathic 
  (or 
  feldspa- 
  

   thoidic) 
  and 
  of 
  mafic 
  minerals 
  is 
  provided. 
  The 
  term 
  mafic, 
  it 
  

   may 
  be 
  added, 
  is 
  a 
  shorter 
  equivalent 
  for 
  ferromagnesian. 
  

  

  On 
  this 
  basis 
  the 
  rocks 
  have 
  been 
  briefly 
  treated, 
  the 
  object 
  

   being 
  to 
  present 
  their 
  mineralogic 
  and 
  chemical 
  characteristics, 
  

   and 
  to 
  bring 
  into 
  correlation 
  the 
  variously 
  named 
  types 
  described 
  

   by 
  petrographers 
  rather 
  than 
  to 
  furnish 
  an 
  encyclopedia 
  of 
  petro- 
  

   graphical 
  data. 
  We 
  believe 
  the 
  author 
  has 
  done 
  well 
  in 
  thus 
  

   restraining 
  himself, 
  for 
  information 
  of 
  this 
  nature 
  is 
  already 
  

   available 
  in 
  the 
  voluminous 
  treatises 
  of 
  Rosenbusch 
  and 
  Zirkel. 
  

   On 
  the 
  chemical 
  side, 
  however, 
  the 
  material 
  is 
  abundant 
  and 
  this 
  

   emphasis 
  of 
  the 
  chemical 
  characteristics 
  of 
  igneous 
  rocks 
  is 
  one 
  of 
  

   the 
  chief 
  and 
  most 
  valuable 
  features 
  of 
  the 
  book. 
  It 
  is 
  shown 
  in 
  

   the 
  presence 
  of 
  *71 
  tables, 
  ench 
  containing 
  from 
  one 
  to 
  two 
  dozen 
  

   well-selected 
  analyses, 
  with 
  their 
  calculated 
  norms. 
  The 
  apha- 
  

   nitic 
  rocks 
  are 
  treated 
  in 
  close 
  connection 
  with 
  their 
  chemically 
  

   equivalent 
  phanerites, 
  thus 
  showing 
  the 
  varied 
  forms 
  of 
  crystalli- 
  

   zation 
  of 
  chemically 
  similar 
  magmas. 
  

  

  The 
  second 
  portion 
  of 
  the 
  work 
  devoted 
  to 
  the 
  occurrence 
  of 
  

   igneous 
  rocks 
  furnishes 
  the 
  most 
  comprehensive 
  treatment 
  of 
  the 
  

   problem 
  of 
  petrographical 
  provinces 
  which 
  has 
  been 
  attempted. 
  

   After 
  a 
  general 
  discussion 
  each 
  great 
  division 
  of 
  the 
  earth 
  is 
  con- 
  

   sidered 
  in 
  detail 
  and 
  the 
  occurrence 
  of 
  its 
  igneous 
  rocks 
  is 
  shown 
  

   upon 
  a 
  colored 
  map, 
  which 
  facilitates 
  the 
  perception 
  of 
  their 
  

   separation 
  into 
  different 
  provinces. 
  In 
  Europe, 
  for 
  example, 
  they 
  

   are 
  considered 
  after 
  the 
  following 
  grouping 
  : 
  

  

  1 
  Scandinavia 
  and 
  Finland. 
  

  

  2 
  Ural 
  Mountains. 
  

  

  3 
  British 
  Isles. 
  

  

  4 
  France, 
  Spain, 
  Portugal. 
  

  

  