﻿574 
  Scientific 
  Intelligence. 
  

  

  appended. 
  The 
  colored 
  chart 
  of 
  Michel-Levy 
  for 
  maximum 
  

   birefringences 
  and 
  the 
  table 
  of 
  the 
  chief 
  characters 
  of 
  the 
  rock 
  

   minerals 
  will 
  be 
  found 
  useful 
  in 
  identification. 
  

  

  On 
  the 
  whole 
  the 
  author 
  has 
  done 
  his 
  work 
  well, 
  the 
  chief 
  

   fault 
  being 
  that 
  which 
  is 
  necessarily 
  inherent 
  in 
  books 
  of 
  this 
  

   class, 
  where 
  the 
  attempt 
  is 
  made 
  to 
  compress 
  into 
  so 
  small 
  a 
  com- 
  

   pass 
  any 
  comprehensive 
  account 
  of 
  such 
  a 
  great 
  mass 
  of 
  material 
  

   as 
  the 
  subject 
  of 
  petrology 
  affords. 
  It 
  should 
  not 
  be 
  understood, 
  

   however, 
  that, 
  as 
  is 
  so 
  often 
  the 
  case, 
  the 
  book 
  is 
  a 
  mere 
  synopsis. 
  

   The 
  author 
  has 
  wisely 
  restricted 
  himself 
  to 
  a 
  relatively 
  few 
  

   important 
  matters 
  and 
  has 
  treated 
  these 
  with 
  a 
  fair 
  degree 
  of 
  

   fullness. 
  It 
  is 
  only 
  in 
  the 
  description 
  of 
  the 
  rocks 
  that 
  the 
  

   synoptic 
  character 
  becomes 
  evident 
  and 
  it 
  would 
  seem 
  as 
  if 
  this 
  

   part 
  of 
  the 
  work 
  might 
  have 
  been 
  somewhat 
  more 
  expanded, 
  

   with 
  advantage 
  to 
  the 
  student. 
  

  

  For 
  those 
  who 
  desire 
  to 
  obtain 
  a 
  general 
  notion 
  of 
  the 
  science 
  

   of 
  petrology, 
  to 
  familiarize 
  themselves 
  with 
  the 
  method 
  of 
  deter- 
  

   mining 
  the 
  common 
  igneous 
  rocks 
  by 
  the 
  use 
  of 
  the 
  microscope 
  

   and, 
  provided 
  a 
  chemical 
  analysis 
  of 
  a 
  rock 
  has 
  been 
  made, 
  to 
  

   properly 
  calculate 
  its 
  position 
  in 
  the 
  quantitative 
  system, 
  this 
  

   little 
  book, 
  which 
  occupies 
  a 
  distinct 
  place 
  of 
  its 
  own, 
  will 
  be 
  

   found 
  very 
  useful. 
  It 
  is 
  well 
  printed 
  and 
  conveniently 
  bound. 
  

  

  l. 
  v. 
  P. 
  

  

  9. 
  Der 
  Vulcanismns 
  ; 
  von 
  F. 
  vo:n 
  Wolff. 
  2 
  vols. 
  ; 
  vol. 
  1, 
  

   first 
  half. 
  8°, 
  pp. 
  300, 
  80 
  figs. 
  Stuttgart, 
  1913 
  (F. 
  Enke).— 
  This 
  

   is 
  intended 
  as 
  a 
  rather 
  comprehensive 
  work 
  on 
  the 
  igneous 
  activ- 
  

   ities 
  of 
  the 
  earth. 
  This 
  may 
  be 
  seen 
  from 
  the 
  subjects 
  of 
  various 
  

   chapters; 
  thus 
  chapter 
  two 
  treats 
  of 
  the 
  theater 
  of 
  volcanic 
  activ- 
  

   ity 
  and 
  the 
  physical 
  conditions 
  ruling 
  there, 
  chapter 
  three 
  gives 
  

   a 
  full 
  discussion 
  of 
  the 
  properties 
  of 
  the 
  magma, 
  of 
  the 
  process 
  of 
  

   crystallization, 
  structure 
  of 
  the 
  rocks, 
  gaseous 
  components, 
  etc. 
  

   Then 
  follows 
  the 
  treatment 
  of 
  the 
  magmatic 
  zone, 
  in 
  which 
  the 
  

   geographic 
  distribution 
  of 
  igneous 
  rocks, 
  differentiation, 
  assimi- 
  

   lation, 
  and 
  kindred 
  subjects 
  are 
  considered. 
  Next 
  the 
  geologic 
  

   mode 
  of 
  occurrence 
  of 
  intrusive 
  rocks 
  and 
  the 
  mechanics 
  of 
  intru- 
  

   sion 
  are 
  dealt 
  with 
  in 
  detail. 
  Post 
  volcanic 
  processes 
  connected 
  

   with 
  intrusions, 
  that 
  is 
  to 
  say 
  contact 
  metamorphism, 
  follow, 
  and 
  

   the 
  present 
  portion 
  ends 
  with 
  an 
  account 
  of 
  submarine 
  eruptions. 
  

  

  The 
  literature 
  of 
  the 
  various 
  subjects 
  is 
  quite 
  fully 
  considered, 
  

   the 
  author 
  giving 
  short, 
  clear 
  statements 
  of 
  the 
  views 
  of 
  other 
  

   writers, 
  accompanied 
  by 
  critical 
  comments 
  of 
  his 
  own. 
  He 
  has 
  

   introduced 
  considerable 
  original 
  matter, 
  and 
  this 
  and 
  the 
  clear 
  

   method 
  of 
  presentation, 
  as 
  well 
  as 
  the 
  references 
  to 
  the 
  work 
  of 
  

   others, 
  make 
  the 
  book 
  not 
  only 
  interesting 
  but 
  very 
  useful 
  for 
  

   investigators 
  and 
  teachers 
  in 
  this 
  field 
  of 
  geology. 
  It 
  is 
  well 
  and 
  

   clearly 
  printed, 
  but 
  some 
  of 
  the 
  figures, 
  introduced 
  from 
  the 
  older 
  

   works, 
  are 
  for 
  a 
  modern 
  one 
  rather 
  crude. 
  While 
  the 
  work 
  is 
  

   to 
  be 
  distinctly 
  commended, 
  and 
  there 
  is 
  no 
  opportunity 
  here 
  for 
  

   a 
  critical 
  review 
  of 
  the 
  subject-matter, 
  one 
  detail 
  may 
  be 
  consid- 
  

   ered. 
  In 
  treating 
  of 
  the 
  geographical 
  distribution 
  of 
  igneous 
  

  

  