﻿HAtTGHTON 
  GRANITES 
  OF 
  IRELAND. 
  

  

  269 
  

  

  investigation, 
  I 
  hope 
  to 
  be 
  able 
  to 
  show 
  that 
  the 
  mineralogical 
  

   composition 
  of 
  a 
  granite 
  is 
  a 
  problem 
  of 
  much 
  greater 
  difficulty 
  than 
  

   is 
  commonly 
  supposed, 
  and 
  that 
  the 
  number 
  of 
  minerals 
  entering 
  

   into 
  its 
  composition 
  is 
  greater 
  than 
  that 
  visible 
  to 
  the 
  eye, 
  or 
  to 
  be 
  

   detected 
  by 
  physical 
  characters. 
  

  

  In 
  order 
  to 
  save 
  the 
  trouble 
  of 
  reference 
  to 
  my 
  former 
  paper, 
  I 
  

   here 
  reproduce 
  the 
  Tables 
  containing 
  the 
  chemical 
  composition 
  of 
  

   the 
  granites 
  and 
  of 
  their 
  four 
  supposed 
  constituents, 
  together 
  with 
  

   the 
  table 
  containing 
  the 
  oxygen-proportions 
  of 
  those 
  constituent 
  

   minerals. 
  

  

  Table 
  I. 
  

  

  Chemical 
  Composition 
  of 
  Donegal 
  Granites 
  (Table 
  IV. 
  he. 
  cit.). 
  

  

  No. 
  

  

  

  Alumina. 
  

  

  Iron, 
  

   peroxide. 
  

  

  q3 
  

   M 
  

  

  o 
  p 
  

  

  a 
  

   3 
  

  

  .03 
  

   "S3 
  

  

  fee 
  

  

  03 
  

  

  03 
  

   O 
  

  

  03 
  

  

  O 
  

  

  03 
  O 
  

  

  © 
  

  

  03 
  

  

  r 
  c3 
  

   O 
  

  

  H 
  

  

  

  70-00 
  

   65-80 
  

   68-96 
  

   58-44 
  

   69-36 
  

   68-00 
  

   68-20 
  

   70-64 
  

   72-24 
  

   73-60 
  

   68-80 
  

   69-20 
  

   55-20 
  

   75-24 
  

   73-04 
  

  

  16-36 
  

  

  12-80 
  

   17-40 
  

   20-00 
  

   16-00 
  

   16-80 
  

   15-96 
  

   15-64 
  

   14-92 
  

   13-80 
  

   16-40 
  

   16-40 
  

   19-28 
  

   13-36 
  

   15-20 
  

  

  2-80 
  

   6-64 
  

   2-52 
  

   644 
  

   303 
  

   3-68 
  

   3-69 
  

   2-64 
  

   1-63 
  

   2-00 
  

   2-60 
  

   209 
  

   6-08 
  

  

  008 
  

   018 
  

  

  205 
  

   0-30 
  

   0-65 
  

   100 
  

  

  023 
  

  

  6-65 
  

  

  1-00 
  

   0-46 
  

  

  112 
  

   2-92 
  

   2-80 
  

   4-72 
  

   2-29 
  

   4-05 
  

   2-92 
  

   2-47 
  

   1-68 
  

   0-79 
  

   1-75 
  

   1-03 
  

   5-08 
  

   2-25 
  

   1-60 
  

  

  0-71 
  

  

  1-78 
  

   0-41 
  

   1-57 
  

   0-54 
  

   0-95 
  

   0-78 
  

   0-15 
  

   036 
  

   0-50 
  

   0-85 
  

   0-85 
  

   3-66 
  

   0-14 
  

   0-07 
  

  

  4-13 
  

   4-16 
  

   3-03 
  

   3-81 
  

   4-17 
  

   4-32 
  

   3-75 
  

   3-81 
  

   3-51 
  

   4-29 
  

   3-78 
  

   4-20 
  

   4-63 
  

   4-86 
  

   2-88 
  

  

  4-66 
  

   4-40 
  

   5-25 
  

   2-82 
  

   4-47 
  

   2-04 
  

   4-14 
  

   4-53 
  

   5-10 
  

   5-22 
  

   5-31 
  

   5-22 
  

   3-17 
  

   3-27 
  

   7-32 
  

  

  6-32 
  

   0-96 
  

  

  1-20 
  

  

  99-86 
  

  

  99-88 
  

  

  100-37 
  

  

  Q9-8.^ 
  

  

  II. 
  Urrismenagh 
  

  

  III. 
  Glen 
  

  

  IV. 
  Glen 
  

  

  V. 
  Glenveaeh 
  

  

  ... 
  100-16 
  

  

  VI. 
  Glenveagh 
  

  

  6 
  ; 
  64 
  

  

  100-49 
  

  

  10044 
  

  

  99-88 
  

  

  99-99 
  

  

  100-20 
  

  

  100-14 
  

  

  99-99 
  

  

  99-16 
  

  

  99-72 
  

  

  100-11 
  

  

  VII. 
  Poison 
  Glen 
  

  

  VIII. 
  Poison 
  Glen 
  . 
  . 
  , 
  

   IX. 
  Doocharry 
  Bridge 
  

  

  XII. 
  Tory 
  Island 
  

   XIII. 
  Ardara 
  

  

  

  0-60! 
  ... 
  

  

  XV. 
  Annagary 
  

  

  

  

  1 
  

  

  

  

  

  

  Table 
  II. 
  — 
  Mean 
  Composition 
  of 
  the 
  Constituent 
  Minerals 
  of 
  the 
  

   Granite 
  of 
  Donegal 
  (Table 
  X. 
  he. 
  cit.). 
  

  

  

  Quartz. 
  

  

  i 
  . 
  i 
  

   Orthoclase. 
  Oligoclase. 
  (Black 
  Mica. 
  

  

  Silica 
  

  

  100-00 
  

  

  63-20 
  

  

  18-64 
  

  

  0-68 
  

  

  59-92 
  

   23-68 
  

   117 
  

   005 
  

   0-16 
  

   5-30 
  

   0-13 
  

   6-47 
  

   2-07 
  

  

  36-18 
  

   17-68 
  

   26-75 
  

   0-63 
  

   0-95 
  

   0-54 
  

   4-65 
  

   0-32 
  

   8-83 
  

   315 
  

  

  Alumina 
  

  

  Iron 
  (peroxide) 
  

  

  

  Iron 
  (protoxide) 
  

  

  

  Protoxide 
  of 
  Manganese 
  

  

  Lime 
  

  

  

  

  

  2-75 
  

  

  0-11 
  

  

  0-78 
  

  

  14-92 
  

  

  Magnesia 
  

  

  

  Soda 
  

  

  

  Potash 
  

  

  

  Water 
  

  

  

  

  

  

  

  Totals 
  

  

  10000 
  

  

  10108 
  

  

  98-95 
  

  

  99 
  68 
  

  

  

  