﻿A. 
  P. 
  lioness 
  — 
  Etching 
  Figures 
  of 
  Beryl. 
  231 
  

  

  figures, 
  were 
  immersed 
  for 
  fifteen 
  seconds. 
  Nevertheless, 
  

   large, 
  well-defined 
  etchings 
  were 
  obtained, 
  which 
  may 
  be 
  easily 
  

   compared 
  with 
  those 
  previously 
  described. 
  These 
  figures, 
  as 
  

   before 
  mentioned, 
  do 
  not 
  resemble 
  the 
  potassium 
  figures 
  to 
  as 
  

   great 
  a 
  degree 
  as 
  they 
  do 
  those 
  produced 
  by 
  sodium 
  hydroxide, 
  

   and 
  a 
  comparison 
  will 
  eventually 
  evolve 
  into 
  slight 
  modifica- 
  

   tions 
  of 
  the 
  sodium 
  forms. 
  In 
  the 
  first 
  place 
  a 
  detailed 
  study 
  

   of 
  the 
  sodium-potassium 
  etchings 
  (fig. 
  7) 
  reveals 
  four 
  slightly 
  

   curved 
  bounding 
  lines 
  instead 
  of 
  two, 
  as 
  described 
  in 
  the 
  

   sodium 
  figures. 
  Also 
  these 
  figures 
  are 
  deeper 
  with 
  a 
  larger 
  

   plane 
  lying 
  parallel 
  to 
  the 
  prism 
  face 
  ; 
  in 
  most 
  of 
  the 
  larger 
  

   figures 
  the 
  basal 
  groove 
  so 
  prominent 
  in 
  the 
  sodium 
  figures 
  is 
  

   noticeably 
  absent. 
  These 
  characteristics 
  reveal 
  the 
  presence 
  of 
  

   the 
  potassium 
  molecule, 
  in 
  the 
  mixture, 
  as 
  they 
  are 
  quite 
  com- 
  

   mon 
  in 
  the 
  forms 
  produced 
  by 
  that 
  fusion. 
  It 
  is 
  possible 
  that 
  

   they 
  are 
  shorter 
  and 
  thicker 
  than 
  either 
  of 
  the 
  others. 
  But, 
  

   on 
  the 
  whole, 
  the 
  shape 
  of 
  the 
  figures 
  and 
  their 
  orientation 
  

   resemble 
  very 
  closely 
  the 
  sodium 
  figures. 
  Other 
  etchings 
  ap- 
  

   pear 
  on 
  the 
  same 
  face 
  representing 
  various 
  stages 
  of 
  growth, 
  and 
  

   even 
  these 
  bear 
  much 
  resemblance 
  to 
  the 
  sodium 
  forms. 
  They 
  

   are 
  not 
  so 
  deep 
  and 
  possess 
  a 
  large 
  plane 
  parallel 
  to 
  the 
  unit 
  

   prism 
  1010 
  ; 
  oftentimes 
  they 
  are 
  so 
  shallow 
  as 
  to 
  be 
  barely 
  

   visible 
  under 
  the 
  microscope, 
  and 
  still 
  they 
  are 
  about 
  the 
  size 
  

   of 
  mature 
  figures. 
  Etchings 
  of 
  this 
  kind 
  have 
  little 
  detail, 
  

   revealing 
  practically 
  nothing 
  to 
  the 
  observer, 
  except 
  a 
  broad 
  

   flat 
  plane, 
  which 
  gradually 
  diminishes 
  in 
  size 
  as 
  the 
  figure 
  

   deepens, 
  due 
  to 
  the 
  development 
  of 
  the 
  lateral 
  bounding 
  faces. 
  

   In 
  the 
  mature 
  figure, 
  these 
  lateral 
  faces 
  are 
  much 
  more 
  

   prominent 
  than 
  the 
  plane 
  forming 
  the 
  base 
  of 
  the 
  pit. 
  Occa- 
  

   sionally 
  among 
  the 
  smaller 
  figures, 
  well-defined 
  pits 
  occur, 
  

   which 
  are 
  bounded 
  by 
  four 
  triangular 
  faces, 
  the 
  apices 
  of 
  

   which 
  meet 
  in 
  a 
  common 
  point, 
  at 
  the 
  center 
  of 
  the 
  figure 
  

   (see 
  fig. 
  8). 
  These 
  smaller 
  forms 
  appear 
  to 
  be 
  identical 
  with 
  

   natural 
  etchings 
  on 
  Brazilian 
  beryl 
  crystals 
  described 
  by 
  

   Kohlmann.* 
  There 
  is, 
  then, 
  a 
  very 
  noticeable 
  resemblance 
  in 
  

   the 
  two 
  types 
  of 
  etch 
  figures 
  ; 
  those 
  produced 
  by 
  the 
  pure 
  

   sodium 
  hydroxide 
  and 
  those 
  produced 
  by 
  the 
  one 
  to 
  one 
  mix- 
  

   ture 
  of 
  sodium 
  and 
  potassium 
  hydroxides 
  ; 
  and, 
  although 
  

   the 
  figures 
  of 
  different 
  size 
  and 
  shape 
  occur 
  on 
  the 
  same 
  face, 
  

   which 
  merely 
  indicates 
  a 
  variation 
  in 
  conditions 
  of 
  etchings, 
  

   each 
  form 
  reveals 
  very 
  clearly 
  the 
  symmetry 
  of 
  the 
  face 
  upon 
  

   which 
  it 
  occurs, 
  and 
  the 
  several 
  fundamental 
  forms 
  etched 
  

   serve 
  conclusively 
  to 
  illustrate 
  the 
  holohedral 
  character 
  of 
  

   beryl. 
  

  

  Natural 
  Etchings. 
  

  

  Prisms. 
  — 
  The 
  writer, 
  in 
  his 
  investigation 
  of 
  the 
  beryl 
  

   crystals 
  from 
  some 
  of 
  the 
  more 
  important 
  localities, 
  has 
  been 
  

  

  