﻿Notes 
  upon 
  the 
  Litholooy 
  op 
  the 
  Adikondacks. 
  99 
  

  

  similar 
  equivalent 
  volume, 
  while 
  orthoclase 
  belongs 
  to 
  a 
  homo- 
  

   logous 
  genus, 
  which 
  is 
  Meo 
  O 
  w 
  . 
  The 
  formulas 
  with 
  their 
  densi- 
  

   ties 
  and 
  equivalent 
  volumes, 
  are 
  as 
  follows 
  : 
  — 
  

  

  Density. 
  Eq. 
  Vol. 
  

  

  Anorthite 
  (Si 
  32 
  al 
  M 
  Ca 
  8 
  ) 
  64 
  2.76 
  405.0 
  

  

  Albite 
  (Si 
  48 
  al 
  12 
  Na^O^ 
  2.62 
  402.4 
  

  

  Petalite 
  (Si 
  51 
  al 
  10 
  Li 
  3 
  ) 
  64 
  2.45 
  401.5 
  

  

  Orthoclase 
  (Si 
  45 
  al 
  12 
  K 
  3 
  ) 
  O 
  60 
  2.56 
  402.6 
  

  

  Between 
  anorthite 
  and 
  albite, 
  may 
  be 
  placed 
  yosgite, 
  labro- 
  

   dorite, 
  andesine, 
  and 
  oligoclase, 
  whose 
  composition 
  and 
  densi- 
  

   ties 
  are 
  such 
  that 
  they 
  all 
  enter 
  into 
  the 
  same 
  general 
  formula 
  

   with 
  them, 
  and 
  have 
  the 
  same 
  equivalent 
  volume. 
  The 
  results 
  

   of 
  their 
  analyses 
  are 
  by 
  no 
  means 
  constant, 
  and 
  it 
  is 
  probable 
  

   that 
  many, 
  if 
  not 
  all 
  of 
  them, 
  may 
  be 
  but 
  variable 
  mixtures 
  of 
  

  

  albite 
  and 
  anorthite 
  The 
  small 
  portions 
  of 
  lime 
  and 
  potash 
  

  

  in 
  many 
  albites, 
  and 
  of 
  soda 
  in 
  anorthite, 
  petalite 
  and 
  ortho- 
  

   clase, 
  are 
  to 
  be 
  ascribed 
  to 
  mixtures 
  of 
  other 
  feldspar 
  species." 
  

  

  These 
  views 
  were 
  enunciated 
  in 
  the 
  language, 
  which 
  we 
  have 
  

   purposely 
  transcribed 
  literally, 
  twenty-three 
  years 
  ago 
  in 
  the 
  

   American 
  Journal 
  of 
  Science 
  for 
  September, 
  1854. 
  

  

  In 
  1865, 
  in 
  a 
  memoir 
  published 
  in 
  the 
  Proceedings 
  of 
  the 
  

   Academy 
  of 
  Sciences 
  of 
  Vienna, 
  and 
  of 
  which 
  an 
  abstract 
  was 
  

   published 
  in 
  the 
  same 
  year 
  in 
  the 
  Annalen 
  der 
  Physik 
  und 
  

   Chemie, 
  Tschermak 
  adopted 
  these 
  views 
  of 
  Hunt, 
  but 
  in 
  such 
  a 
  

   manner 
  as 
  greatly 
  to 
  impair 
  their 
  original 
  value 
  and 
  significance. 
  

   He 
  states 
  that 
  Hunt 
  had 
  enunciated 
  the 
  proposition, 
  that 
  the 
  

   triclinic 
  feldspars 
  are 
  to 
  be 
  looked 
  upon 
  as 
  mixtures 
  of 
  lime 
  

   and 
  soda 
  feldspars. 
  But 
  on 
  the 
  ground 
  that 
  the 
  analyses 
  show 
  

   in 
  numerous 
  instances 
  the 
  lime 
  and 
  soda 
  feldspars 
  are 
  present 
  

   in 
  molecular 
  proportions, 
  he 
  regards 
  this 
  mixture 
  as 
  a 
  mixture 
  

   in 
  definite 
  relative 
  proportions, 
  or 
  in 
  other 
  words, 
  a 
  molecular 
  

   combination. 
  He 
  makes 
  oligoclase 
  consist 
  of 
  ten 
  molecules 
  of 
  

   albite 
  and 
  three 
  of 
  anorthite, 
  labradorite 
  of 
  two 
  of 
  albite 
  and 
  

   three 
  of 
  anorthite, 
  with 
  many 
  intermediate 
  feldspars, 
  composed 
  

   however 
  in 
  every 
  instance 
  of 
  definite 
  numbers 
  of 
  molecules. 
  In 
  

   these 
  views 
  he 
  has 
  been 
  followed 
  by 
  E-ammelsberg 
  in 
  the 
  late 
  

   edition 
  of 
  the 
  Handbuch 
  der 
  Mineral 
  chemie, 
  1875, 
  who, 
  after 
  

   crediting 
  Tschermak 
  with 
  having 
  originated 
  the 
  theorem 
  — 
  that 
  

   all 
  lime-soda 
  feldspars 
  are 
  to 
  be 
  regarded 
  as 
  isomorphous 
  mix- 
  

   tures 
  of 
  anorthite 
  and 
  albite, 
  applies 
  it 
  to 
  the 
  computation 
  of 
  

  

  