﻿158 
  Iwasaki 
  — 
  Orthoclase 
  Crystals 
  from 
  Shinano, 
  Japan. 
  

  

  III. 
  Baveno 
  Trillings. 
  — 
  The 
  crystals 
  are 
  most 
  frequently 
  

   twinned 
  after 
  the 
  Baveno 
  type 
  in 
  the 
  cyclical 
  order, 
  and 
  form 
  the 
  

   same 
  individual 
  as 
  so-called 
  " 
  Drilling 
  " 
  of 
  Xaumann.^" 
  If 
  these 
  

   three 
  individuals 
  be 
  noted 
  as 
  A, 
  B, 
  and 
  C 
  (fig. 
  4), 
  the 
  prismatic 
  

   faces 
  of 
  A 
  and 
  C 
  are 
  in 
  juxtaposition 
  forming 
  a 
  groove 
  between 
  

   these 
  two 
  faces. 
  The 
  most 
  simple 
  case 
  of 
  this 
  type 
  is 
  shown 
  

  

  \ 
  

  

  

  A 
  

  

  

  

  X 
  

  

  

  

  V 
  

  

  L 
  

  

  

  \ 
  

  

  in 
  fig. 
  4. 
  Often 
  the 
  groove 
  proceeds 
  into 
  B, 
  and 
  two 
  faces 
  of 
  

   the 
  prism 
  of 
  the 
  same 
  individuals 
  make 
  a 
  reentrant 
  angle 
  (201) 
  

   sometimes 
  (101) 
  being 
  divided 
  into 
  two 
  areas. 
  The 
  devel- 
  

   opment 
  of 
  the 
  crystal 
  faces 
  on 
  both 
  sides 
  of 
  the 
  groove 
  

   commonly 
  takes 
  place 
  to 
  the 
  same 
  extent. 
  But 
  sometimes 
  

   they 
  are 
  unequal 
  as 
  shown 
  in 
  fig. 
  8. 
  

  

  IV. 
  Baveno 
  Fourling 
  (fig. 
  9). 
  — 
  Finally 
  four 
  crystals 
  are 
  

   twinned 
  in 
  the 
  cyclical 
  order, 
  forming 
  the 
  so-called 
  " 
  Vierling'' 
  

   of 
  Naumann, 
  eight 
  faces 
  of 
  the 
  prism 
  of 
  the 
  four 
  individuals 
  

   meeting 
  each 
  other, 
  forming 
  the 
  adjacent 
  faces, 
  and 
  at 
  the 
  

   same 
  time 
  making 
  a 
  hollow 
  pit 
  in 
  the 
  center 
  of 
  the 
  top 
  of 
  the 
  

   longer 
  diameter 
  of 
  the 
  crystal. 
  The 
  four 
  faces 
  parallel, 
  the 
  

   longer 
  diameter 
  consists 
  of 
  four 
  basal 
  faces, 
  while 
  the 
  clinopina- 
  

   coids 
  are 
  wholly 
  hidden. 
  Hessenbergf 
  describes 
  such 
  crystals 
  

   from 
  Orfano 
  of 
  Italy. 
  The 
  orthoclase 
  here 
  described 
  is 
  sim- 
  

   pler 
  than 
  his, 
  and 
  does 
  not 
  form 
  the 
  " 
  4 
  tower 
  in 
  the 
  four 
  

   corners" 
  described 
  by 
  him, 
  but 
  only 
  the 
  hollow 
  pit 
  in 
  the 
  

   center. 
  

  

  * 
  Hintze, 
  Haudbuch 
  der 
  Mineralogie, 
  ii, 
  1341. 
  

   f 
  Min. 
  Not., 
  18G7, 
  iv, 
  45, 
  183, 
  v, 
  15. 
  

  

  