﻿22 
  Penjield 
  and 
  Warren 
  — 
  Composition 
  of 
  Parisite. 
  

  

  could 
  be 
  made 
  with 
  the 
  reflecting 
  goniometer 
  and 
  are 
  given 
  in 
  

   an 
  accompanying 
  table. 
  Some 
  of 
  the 
  edges 
  of 
  the 
  pyramid 
  o 
  

   are 
  truncated 
  by 
  a 
  pyramid 
  of 
  the 
  second 
  order 
  s 
  (1121), 
  also 
  

   in 
  oscillatory 
  combination, 
  but, 
  as 
  shown 
  in 
  the 
  figure, 
  this 
  

   form 
  generally 
  is 
  not 
  continuous 
  throughout 
  

   the 
  whole 
  length 
  of 
  the 
  shaft 
  nor 
  is 
  it 
  present 
  

   on 
  all 
  the 
  edges. 
  The 
  pyramid 
  _which 
  finally 
  

   terminates 
  the 
  crystals 
  is 
  r 
  (2023). 
  This 
  is 
  

   generally 
  quite 
  distinct, 
  although 
  its 
  middle 
  

   edges 
  are 
  somewhat 
  rounded 
  by 
  a 
  system 
  of 
  

   fine 
  horizontal 
  stnations. 
  The 
  prism 
  of 
  the 
  

   second 
  order 
  a 
  (1120), 
  represented 
  in 
  the 
  figure, 
  

   is 
  always 
  small 
  and 
  frequently 
  wanting. 
  The 
  

   prism 
  of 
  the 
  first 
  order, 
  m 
  (1010), 
  was 
  not 
  

   observed 
  as 
  a 
  distinct 
  face, 
  although 
  the 
  oscil- 
  

   latory 
  combination 
  of 
  the 
  upper 
  and 
  lower 
  

   pyramidal 
  faces 
  often 
  gave 
  rise 
  to 
  striated, 
  

   rounded, 
  surfaces 
  which 
  approximate 
  in 
  posi- 
  

   tion 
  to 
  the 
  faces 
  of 
  this 
  prism. 
  Occasionally 
  

   the 
  shafts 
  taper 
  to 
  a 
  point 
  withoutjthe 
  enlarged 
  

   pyramid. 
  Of 
  the 
  forms 
  observed, 
  a 
  (1120), 
  r 
  (2023), 
  o 
  (203l), 
  

   5 
  (1121) 
  and 
  m?(1010), 
  the 
  prism 
  a 
  is 
  new. 
  The 
  angles 
  

   which 
  were 
  measured 
  are 
  given 
  below, 
  together 
  with 
  the 
  values 
  

   calculated 
  from 
  the 
  vertical 
  axis 
  established 
  by 
  Des 
  Cloizeaux,* 
  

   c= 
  3-2891. 
  

  

  Measured. 
  

  

  Calculated. 
  

  

  a/s6« 
  = 
  1120^1210= 
  59° 
  54' 
  

  

  60° 
  00' 
  

  

  rxsr= 
  2023 
  /v 
  0223= 
  b6 
  25 
  

  

  55 
  25-1 
  

  

  r/sr 
  =: 
  2023^2023 
  = 
  137 
  22 
  

  

  136 
  54^ 
  

  

  6' 
  ^S 
  =: 
  1121^1121 
  =: 
  17 
  23 
  

  

  17 
  18 
  

  

  0/^0 
  = 
  2021/^2021= 
  13 
  10 
  

  

  14 
  00 
  

  

  For 
  the 
  chemical 
  analysis 
  the 
  best 
  material 
  that 
  could 
  be 
  

   obtained 
  was 
  secured 
  by 
  picking 
  out 
  the 
  crystals 
  from 
  the 
  

   matrix 
  by 
  hand, 
  and 
  rubbing 
  them 
  between 
  the 
  fingers 
  to 
  

   remove 
  any 
  loosely 
  adhering 
  material. 
  The 
  crystals 
  enclosed, 
  

   as 
  has 
  been 
  said, 
  a 
  little 
  pyrite 
  and 
  were 
  not 
  very 
  firm, 
  conse- 
  

   quently 
  some 
  siliceous 
  material 
  was 
  deposited 
  in 
  the 
  cracks. 
  

   These 
  impurities 
  amount 
  to 
  about 
  six 
  per 
  cent. 
  The 
  material 
  

   was 
  of 
  a 
  nearly 
  uniform 
  yellowish 
  brown 
  color. 
  

  

  The 
  method 
  of 
  analysis 
  was 
  as 
  follows 
  : 
  Carbon 
  dioxide 
  was 
  

   obtained 
  by 
  dissolving 
  the 
  mineral 
  in 
  hydrochloric 
  acid 
  and 
  

   collecting 
  the 
  gas 
  evolved 
  in 
  weighed 
  potash 
  bulbs. 
  For 
  

   fluorine, 
  another 
  j)ortion 
  of 
  material 
  was 
  fused 
  with 
  sodium 
  

   carbonate 
  and 
  a 
  weighed 
  amount 
  of 
  silica, 
  and 
  the 
  fluorine 
  

   separated 
  and 
  estimated 
  by 
  the 
  Berzelius 
  method 
  as 
  modified 
  

   by 
  Penfield 
  and 
  Minor. 
  f 
  The 
  earths 
  were 
  sei)arated 
  from 
  

   calcium 
  by 
  repeated 
  precipitations 
  with 
  ammonia, 
  and 
  they 
  

   were 
  then 
  converted 
  into 
  oxalates, 
  ignited, 
  and 
  weighed 
  as 
  

  

  *Min., 
  ii, 
  p. 
  162, 
  1874. 
  f 
  This 
  Journal, 
  III, 
  xlvii, 
  p. 
  387, 
  1894. 
  

  

  