﻿84 
  PEOF. 
  T. 
  G. 
  BONNET 
  ON 
  TWO 
  TEAVEBSES 
  OF 
  THE 
  

  

  over 
  the 
  crystalline 
  rocks 
  of 
  the 
  central 
  range, 
  from 
  which, 
  however, 
  

   they 
  have 
  been 
  almost 
  entirely 
  removed 
  by 
  denudation. 
  Of 
  the 
  

   igneous 
  rocks 
  of 
  the 
  region, 
  especially 
  those 
  of 
  the 
  Southern 
  Tyrol, 
  

   it 
  is 
  needless 
  to 
  speak. 
  The 
  above-named 
  " 
  Thonschiefer" 
  with 
  the 
  

   lower 
  part 
  of 
  which 
  some 
  chloritic 
  schists 
  and 
  crystalline 
  limestones 
  

   are 
  associated, 
  is 
  extensively 
  developed 
  in 
  the 
  Eastern 
  Alps. 
  The 
  name 
  

   " 
  Thonschiefer 
  " 
  is 
  vague 
  ; 
  for, 
  if 
  I 
  mistake 
  not, 
  it 
  might 
  be 
  applied 
  

   to 
  either 
  a 
  claj^-slate 
  or 
  an 
  aluminous 
  schist. 
  Certainly 
  the 
  rock 
  is 
  

   not 
  the 
  former, 
  though 
  sometimes 
  locally, 
  when 
  greatly 
  crushed, 
  it 
  

   presents 
  a 
  stroug 
  resemblance 
  to 
  it. 
  In 
  the 
  extensive 
  rock-collec- 
  

   tion 
  of 
  the 
  Innsbruck 
  Museum 
  the 
  series 
  is 
  called 
  " 
  Thon-glimmer- 
  

   Schiefer" 
  which 
  is 
  made 
  less 
  ambiguous 
  by 
  the 
  inserted 
  word. 
  I 
  

   have 
  a 
  difficulty 
  in 
  finding 
  an 
  English 
  equivalent. 
  Clay 
  -mica- 
  

   schist 
  is 
  misleading, 
  aluminous 
  mica-schist 
  awkward 
  ; 
  upper 
  mica- 
  

   schist 
  is 
  open 
  to 
  objection 
  as 
  involving 
  an 
  assumption 
  as 
  to 
  strati- 
  

   graphy 
  ; 
  phyllite 
  suggests 
  too 
  fine-grained 
  a 
  rock 
  ; 
  so 
  I 
  propose, 
  at 
  

   present, 
  in 
  the 
  poverty 
  of 
  English 
  nomenclature, 
  to 
  retain 
  the 
  

   German 
  term 
  " 
  Thonglimmerschiefer." 
  

  

  (/3) 
  The 
  Pusterthal 
  and 
  Neighbourhood. 
  

  

  "We 
  travelled 
  by 
  railway 
  up 
  the 
  valley 
  of 
  the 
  Adige, 
  traversed 
  

   the 
  igneous 
  rocks 
  in 
  the 
  neighbourhood 
  of 
  Bozen, 
  and 
  in 
  due 
  course 
  

   reached 
  the 
  " 
  Thonglimmerschiefer 
  " 
  south 
  of 
  Klausen 
  *. 
  With 
  the 
  

   members 
  of 
  this 
  group 
  previous 
  visits 
  to 
  the 
  Tyrol 
  had 
  already 
  

   made 
  me 
  fairly 
  familiar, 
  and 
  I 
  could 
  see, 
  even 
  as 
  I 
  passed 
  by, 
  that 
  

   though 
  they 
  varied 
  somewhat 
  in 
  texture 
  and 
  hardness, 
  the 
  dominant 
  

   rock 
  is 
  a 
  moderately 
  soft, 
  dull 
  lead-coloured 
  mica-schist, 
  in 
  which 
  the 
  

   individual 
  films 
  are 
  not 
  coDspicuous 
  to 
  the 
  eye, 
  at 
  any 
  rate 
  at 
  the 
  

   first 
  glance. 
  This 
  obscuration 
  of 
  the 
  true 
  structure 
  is 
  very 
  probably 
  

   the 
  result 
  of 
  crushing. 
  The 
  apparent 
  foliation 
  is 
  a 
  cleavage-foliation 
  

   the 
  conspicuous 
  surfaces 
  are 
  " 
  sheen 
  surfaces," 
  which 
  exhibit 
  a 
  

   peculiar 
  gloss, 
  looking 
  sometimes 
  like 
  the 
  polished 
  black-lead 
  of 
  a 
  

   fire-grate. 
  

  

  These 
  macroscopic 
  characteristics 
  are 
  very 
  commonly 
  so 
  general 
  

   and 
  so 
  uniform, 
  that 
  one 
  can 
  recognize 
  the 
  rock 
  with 
  certainty 
  even 
  

   from 
  a 
  railway-train 
  f. 
  Our 
  first 
  halt 
  was 
  made 
  at 
  Brunecken, 
  

   where. 
  the 
  " 
  Thonglimmerschiefer" 
  series 
  is 
  well 
  exposed 
  close 
  to 
  the 
  

   town, 
  and 
  presents 
  some 
  interesting 
  variations. 
  The 
  picturesque 
  

   old 
  castle 
  stands 
  on 
  a 
  craggy 
  mound 
  of 
  white 
  crystalline 
  limestone 
  

   (Appendix, 
  p. 
  107) 
  ; 
  this, 
  on 
  the 
  southern 
  side, 
  is 
  distinctly 
  " 
  bedded 
  " 
  

   like 
  an 
  ordinary 
  limestone, 
  and 
  dark 
  streaks 
  occur 
  in 
  the 
  rock 
  

   parallel 
  with 
  this 
  structure. 
  The 
  beds 
  are 
  much 
  twisted 
  about, 
  but 
  

   they 
  appear 
  to 
  have 
  a 
  general 
  strike 
  about 
  S.S.E., 
  with 
  a 
  high 
  dip. 
  

  

  On 
  the 
  northern 
  side 
  a 
  little 
  mica-schist 
  crops 
  out, 
  apparently 
  in 
  

   situ 
  ; 
  but 
  its 
  strike 
  is 
  nearer 
  E.S.E. 
  Then 
  comes 
  (after 
  a 
  short 
  

  

  * 
  In 
  several 
  places, 
  as 
  I 
  have 
  myself 
  seen 
  and 
  have 
  learnt 
  from 
  the 
  Innsbruck 
  

   Museum, 
  the 
  dolomites 
  of 
  the 
  Italian 
  Tyrol 
  rest 
  on 
  either 
  " 
  Thonglimmer- 
  

   schiefer^ 
  or 
  mica- 
  schist. 
  

  

  t 
  I 
  have 
  verified 
  this 
  assertion 
  many 
  times. 
  

  

  