﻿278 
  

  

  PROCEEDINGS 
  OF 
  THE 
  GEOLOGICAL 
  SOCIETY. 
  

  

  Table 
  X. 
  — 
  Oxygen 
  contained 
  in 
  the 
  Silica, 
  Peroxides, 
  and 
  Protoxides 
  

  

  of 
  Scotch 
  Granites. 
  

  

  Locality. 
  

  

  Oxygen 
  of 
  

   Silica. 
  

  

  Oxygen 
  of 
  

   peroxides. 
  

  

  Oxygen 
  of 
  

   protoxides. 
  

  

  51-92-Aj. 
  

  

  A 
  r 
  

  

  B. 
  

  

  C. 
  

  

  A. 
  

  

  Strontian 
  

  

  32-19 
  

   36-66 
  

  

  9-66 
  

   812 
  

  

  4-50 
  

   3-10 
  

  

  19-73 
  

   15-26 
  

  

  Tobermurry 
  

  

  Introducing 
  the 
  preceding 
  values 
  of 
  A, 
  B, 
  C 
  into 
  equations 
  (4), 
  

   we 
  find 
  the 
  following 
  per-centages 
  of 
  quartz, 
  orthoclase, 
  oligoclase, 
  

   and 
  black 
  mica 
  : 
  — 
  

  

  Table 
  XI. 
  — 
  Calculated 
  Mineralogical 
  Composition 
  of 
  Scotch 
  

  

  Granites. 
  

  

  Locality. 
  

  

  Orthoclase, 
  

   =x. 
  

  

  Oligoclase, 
  

  

  Black 
  mica, 
  

  

  Quartz, 
  

  

  Strontian 
  

  

  125-94 
  

   3971 
  

  

  4796 
  

   86-50 
  

  

  -43-79 
  

  

  -19-87 
  

  

  -2914 
  

   - 
  5-08 
  

  

  Tobermurry 
  

  

  The 
  negative 
  values 
  of 
  z 
  and 
  u, 
  in 
  the 
  foregoing 
  Table, 
  demon- 
  

   strate 
  that 
  the 
  Scotch 
  granites, 
  like 
  many 
  of 
  those 
  of 
  Donegal, 
  cannot 
  

   be 
  represented 
  by 
  any 
  combination 
  of 
  quartz, 
  orthoclase, 
  oligoclase, 
  

   and 
  black 
  mica 
  ; 
  and 
  yet 
  they 
  contain 
  all 
  those 
  minerals. 
  

  

  The 
  granites 
  of 
  Norway, 
  Sweden, 
  and 
  Finland, 
  so 
  far 
  as 
  I 
  have 
  

   had 
  an 
  opportunity 
  of 
  examining 
  them 
  in 
  the 
  field, 
  have 
  the 
  same 
  

   stratified 
  geological 
  structure 
  as 
  the 
  granites 
  of 
  Donegal, 
  and 
  they 
  

   •are 
  composed 
  of 
  the 
  same 
  constituent 
  materials, 
  namely, 
  1, 
  Quartz 
  ; 
  

   2, 
  Orthoclase; 
  3, 
  Oligoclase; 
  4, 
  Black 
  mica 
  ; 
  5, 
  White 
  mica 
  (in 
  veins). 
  

  

  I 
  do 
  not 
  remember 
  to 
  have 
  seen 
  hornblende 
  or 
  tourmaline 
  in 
  the 
  

   Swedish 
  granite 
  and 
  gneiss. 
  

  

  The 
  orthoclase 
  is 
  generally 
  pink, 
  and 
  the 
  oligoclase 
  either 
  white 
  

   or 
  waxy 
  greenish, 
  very 
  like 
  the 
  oligoclase 
  of 
  the 
  Garvary 
  Wood 
  

   veins, 
  near 
  Castle 
  Caldwell. 
  

  

  The 
  black 
  mica 
  is 
  much 
  more 
  abundant 
  than 
  the 
  white, 
  which 
  is 
  

   generally 
  found 
  in 
  veins, 
  as 
  in 
  the 
  quarry 
  of 
  Ytterby 
  and 
  other 
  

   celebrated 
  mineral 
  localities. 
  

  

  I 
  have 
  made 
  the 
  following 
  analyses 
  of 
  the 
  constituent 
  minerals 
  

   of 
  the 
  Swedish 
  granite 
  and 
  gneiss. 
  

  

  