﻿I 
  

  

  APR. 
  li), 
  1922 
  wherry: 
  calcium 
  oxalate 
  monohydrate 
  199 
  

  

  Authority 
  Date 
  a 
  ff 
  y 
  y 
  — 
  a 
  2E 
  

  

  Schubert^ 
  1899 
  ... 
  1 
  .549 
  ... 
  ... 
  89° 
  

  

  Becke" 
  1907 
  1.490 
  1.555 
  1.650 
  0.160 
  84° 
  40' 
  

  

  Jezek* 
  1908 
  1 
  .490 
  1 
  .555 
  1 
  .649 
  . 
  159 
  83° 
  42' 
  

  

  Jezek9 
  1911 
  1.491 
  1.555 
  1.650 
  0.159 
  83° 
  55' 
  

  

  Average 
  1 
  490 
  1 
  .555 
  1 
  .650 
  . 
  160 
  84 
  

  

  o 
  

  

  The 
  values 
  given 
  by 
  Becke 
  and 
  by 
  Jezek 
  agree 
  within 
  the 
  limits 
  of 
  

   error 
  of 
  measurement, 
  and 
  the 
  rounded 
  average 
  in 
  the 
  last 
  line 
  may 
  be 
  

   accepted 
  as 
  characteristic 
  of 
  the 
  substance. 
  Examination 
  by 
  the 
  

   immersion 
  method 
  confirmed 
  them 
  completely. 
  The 
  material 
  breaks 
  

   into 
  angular 
  fragments 
  without 
  definite 
  crystallographic 
  orientation, 
  

   so 
  that 
  values 
  intermediate 
  between 
  the 
  several 
  indices 
  are 
  usually 
  

   obtained, 
  but 
  the 
  indices 
  as 
  given 
  appear 
  with 
  sufficient 
  frequency 
  to 
  

   show 
  their 
  correctness. 
  The 
  value 
  of 
  2 
  E, 
  as 
  calculated 
  from 
  2 
  V, 
  is 
  so 
  

   high 
  as 
  not 
  to 
  be 
  measurable 
  under 
  the 
  microscope, 
  but 
  partial 
  figures 
  

   are 
  often 
  seen 
  in 
  the 
  fragments 
  studied 
  by 
  the 
  immersion 
  method, 
  and 
  

   on 
  them 
  the 
  optical 
  sign 
  can 
  be 
  determined 
  as 
  positive, 
  by 
  the 
  use 
  of 
  

   the 
  selenite 
  plate. 
  

  

  The 
  greatest 
  discrepancies 
  in 
  the 
  literature 
  upon 
  whewellite 
  concern 
  

   the 
  optical 
  orientation, 
  the 
  following 
  different 
  descriptions 
  of 
  which 
  

   are 
  given: 
  

  

  Authority 
  Date 
  Position 
  of 
  axial 
  plane 
  Position 
  of 
  acute 
  bisectrix 
  

  

  Becke^" 
  1907 
  Perpendicular 
  to 
  (010) 
  In 
  obtuse 
  angle 
  /329 
  ° 
  from 
  axis 
  c. 
  

  

  Jezekio 
  1908 
  

  

  Winchell" 
  1909 
  " 
  - 
  1 
  1 
  1/2 
  ° 
  from 
  axis 
  c. 
  

  

  Groth'2 
  1910 
  Parallel 
  to 
  (010) 
  In 
  acute 
  angle 
  /364 
  ° 
  from 
  axis 
  c. 
  

  

  Jazek'o 
  1911 
  Perpendicular 
  to 
  (010) 
  In 
  obtuse 
  angle 
  i330 
  ° 
  from 
  axis 
  c. 
  

  

  Study, 
  by 
  the 
  immersion 
  method, 
  of 
  a 
  number 
  of 
  samples, 
  represent- 
  

   ing 
  fragments 
  of 
  the 
  mineral 
  whewellite, 
  crystals 
  in 
  the 
  tissues 
  of 
  vari- 
  

   ous 
  plants, 
  and 
  crystalline 
  precipitates 
  prepared 
  by 
  boiling 
  together 
  

   dilute 
  solutions 
  of 
  the 
  constituent 
  ions, 
  has 
  indicated 
  that 
  the 
  data 
  of 
  

   Becke 
  and 
  Jezek 
  are 
  correct. 
  In 
  accordance 
  with 
  this 
  interpretation 
  

   of 
  the 
  orientation, 
  the 
  following 
  features 
  correspond 
  to 
  the 
  more 
  

   frequent 
  habits: 
  

  

  « 
  Min. 
  petr. 
  Mitth. 
  18: 
  251. 
  1899. 
  

  

  ' 
  Loc. 
  cit. 
  

  

  8 
  Bull. 
  int. 
  Acad. 
  vSci. 
  Bohemia 
  13: 
  1; 
  22: 
  1. 
  1908; 
  through 
  Z. 
  Kryst. 
  Min. 
  46: 
  610. 
  1909. 
  

  

  « 
  Rozpr. 
  Ceske 
  Akad. 
  TI, 
  20: 
  1. 
  1911; 
  through 
  Z. 
  Kryst. 
  Min. 
  54: 
  191. 
  1914. 
  

  

  '° 
  Loc. 
  cit. 
  

  

  '1 
  Elements 
  of 
  optical 
  mineralogy, 
  . 
  391, 
  1919. 
  

  

  '- 
  Chemische 
  Krystallographie 
  3: 
  152. 
  1910. 
  

  

  