﻿45 
  '3 
  DE. 
  C. 
  CALLAWAY 
  OX 
  SECOXLABT 
  MLBTKRAXS 
  ES 
  THE 
  

  

  No. 
  277 
  (PI. 
  XVI. 
  fig?. 
  2. 
  3 
  i 
  was 
  selected 
  from 
  the 
  core 
  of 
  the 
  plexus 
  

   as 
  a 
  specimen 
  of 
  a 
  sound 
  typical 
  gneiss. 
  Bands 
  of 
  foliated 
  kers- 
  

   antite 
  (fig. 
  2) 
  alternate 
  in 
  the 
  slide 
  with 
  a 
  granite-vein 
  or 
  two 
  and 
  

   with 
  the 
  quartzitic 
  gneiss 
  (fig. 
  3) 
  * 
  ; 
  but 
  the 
  micaceous 
  material 
  

   graduates 
  into 
  the 
  more 
  quartzose 
  along 
  the 
  strike 
  as 
  well 
  as 
  trans- 
  

   versely. 
  The 
  passage 
  between 
  the 
  kersantite 
  and 
  the 
  quartzose 
  

   gneiss 
  is. 
  indeed, 
  as 
  complete 
  as 
  possible. 
  There 
  is 
  a 
  larger 
  proportion 
  

   of 
  white 
  mica 
  than 
  in 
  Xo. 
  317. 
  A 
  part 
  of 
  it 
  is 
  not 
  orientated 
  with 
  

   the 
  biotite 
  ; 
  indeed, 
  some 
  small 
  crystals 
  of 
  it. 
  included 
  in 
  the 
  black 
  

   mica, 
  lie 
  with 
  their 
  lamina? 
  almost 
  at 
  right 
  angles 
  to 
  those 
  of 
  the 
  

   biotiie. 
  The 
  felspar 
  crystals 
  of 
  the 
  kersantite 
  sometimes 
  coalesce 
  

   into 
  bands 
  alternating 
  with 
  the 
  biotite. 
  Amongst 
  them 
  is 
  a 
  little 
  

   :iine, 
  and 
  as 
  this 
  mineral 
  has 
  not 
  been 
  detected 
  in 
  the 
  normal 
  

   diorite 
  it 
  is 
  probably 
  secondary. 
  

  

  A 
  vein 
  of 
  granite 
  passing 
  across 
  the 
  slide 
  is 
  of 
  some 
  interest. 
  A 
  

   ezystal 
  of 
  the 
  orthoclase 
  has 
  several 
  cracks 
  in 
  it. 
  One 
  of 
  them 
  is 
  

   nearly 
  7 
  mm. 
  in 
  length, 
  and 
  is 
  filled 
  up 
  almost 
  to 
  the 
  inner 
  extremity 
  

   with 
  black 
  mica. 
  Two 
  or 
  three 
  smaller 
  ones 
  are 
  similarly 
  occupied. 
  

   It 
  appears 
  to 
  be 
  a 
  highly 
  probable 
  conclusion 
  that 
  this 
  mica 
  was 
  

   injected 
  subsequently 
  to 
  the 
  intrusion 
  and 
  consolidation 
  of 
  the 
  vein, 
  

   since 
  it 
  is 
  continuous 
  with 
  the 
  mica 
  of 
  a 
  seam 
  of 
  kersantite. 
  Further 
  

   information 
  on 
  this 
  head 
  will 
  be 
  given 
  in 
  the 
  section 
  on 
  infiltration 
  

   (p. 
  496). 
  

  

  No. 
  31 
  S, 
  from 
  the 
  central 
  part 
  of 
  the 
  zone, 
  is 
  almost 
  a 
  quartzite. 
  

   At 
  the 
  edge 
  of 
  the 
  slide 
  is 
  the 
  foliated 
  kersantite, 
  but 
  the 
  felspar 
  is 
  

   invaded 
  here 
  and 
  there 
  by 
  quartz-granules. 
  The 
  quartz 
  increases 
  in 
  

   quantity 
  towards 
  the 
  other 
  side, 
  so 
  that 
  some 
  parts 
  of 
  the 
  slide 
  

   consist 
  of 
  about 
  three 
  fourths 
  of 
  quartz-granules, 
  and 
  one 
  fourth 
  of 
  

   cloudy 
  felspar 
  with 
  sinuate 
  margins 
  ; 
  a 
  few 
  scraps 
  of 
  biotite, 
  the 
  mere 
  

   rags 
  of 
  the 
  usual 
  flakes, 
  being 
  scattered 
  about. 
  

  

  The 
  conversion 
  of 
  a 
  diorite 
  into 
  such 
  an 
  acidic 
  rock 
  as 
  a 
  gneissose 
  

   quartzite, 
  improbable 
  as 
  the 
  change 
  may 
  seem, 
  receives 
  support 
  from 
  

   an 
  interesting 
  fact 
  recorded 
  by 
  Professor 
  Zirkel 
  f. 
  He 
  says 
  that 
  

   "quartzite 
  as 
  white 
  as 
  snow 
  is 
  interstratified 
  in 
  the 
  hornblende- 
  

   gneisses 
  at 
  the 
  north 
  end 
  of 
  the 
  Park 
  Range.' 
  3 
  The 
  quartz 
  of 
  the 
  

   former 
  contains 
  numerous 
  fiuid-in 
  elusions, 
  which 
  K 
  belong 
  to 
  two 
  

   different 
  varieties, 
  some 
  being 
  composed 
  of 
  water 
  with 
  a 
  moving 
  

   bubble, 
  which 
  does 
  not 
  disappear 
  in 
  a 
  temperature 
  above 
  100^ 
  C, 
  

   and 
  others 
  being 
  the 
  double 
  inclusions 
  i, 
  with 
  carbon 
  dioxide 
  in 
  the 
  

   interior, 
  whose 
  bubble 
  may 
  be 
  driven 
  off 
  by 
  the 
  smoke 
  of 
  a 
  cigar. 
  

   It 
  is 
  remarkable 
  that 
  these 
  inclusions 
  of 
  different 
  chemical 
  nature 
  are 
  

   associated 
  also 
  in 
  the 
  quartzes 
  of 
  the 
  accompanying 
  gneisses, 
  a 
  fact 
  

   which 
  may 
  perhaps 
  prove 
  that 
  the 
  nearest 
  geological 
  connection 
  exists 
  

   between 
  the 
  two 
  rocks, 
  and 
  that 
  in 
  origin 
  they 
  are 
  the 
  same." 
  The 
  

   two 
  kinds 
  of 
  rock 
  referred 
  to 
  by 
  Prof. 
  Zirkel 
  are 
  not 
  much 
  more 
  widely 
  

   different 
  than 
  the 
  two 
  extremes 
  of 
  the 
  series 
  I 
  have 
  just 
  described. 
  

  

  * 
  This 
  figure 
  does 
  not 
  show 
  the 
  extreme 
  of 
  acidification, 
  but 
  was 
  .-: 
  

   because 
  it 
  retained 
  remains 
  of 
  the 
  kersantite 
  structure. 
  

  

  t 
  ' 
  Microscopical 
  Petrography/ 
  Washington, 
  1570,. 
  p 
  33. 
  

  

  * 
  Described 
  on 
  pp. 
  18. 
  19. 
  consisting 
  of 
  an 
  outer 
  solid 
  zone, 
  distinct 
  from 
  the 
  

   matrix, 
  containing 
  liquid 
  carbon-diuxide. 
  

  

  