﻿404 
  Weed 
  and 
  Pirsson 
  — 
  Sulphur, 
  Orpiment, 
  Realgar, 
  etc. 
  

  

  vividly 
  colored 
  pools 
  and 
  equally 
  bright 
  tinted 
  waterways, 
  the 
  

   white 
  sinter 
  flats, 
  and 
  the 
  creamy 
  rose 
  and 
  yellow 
  shades 
  of 
  the 
  

   decomposed 
  rhyolite, 
  the 
  whole 
  surrounded 
  by 
  a 
  setting 
  of 
  

   dark 
  green 
  pines, 
  presents 
  a 
  strange 
  picture 
  not 
  easily 
  for- 
  

   gotten. 
  

  

  The 
  specimens 
  of 
  realgar 
  and 
  orpiment 
  come 
  from 
  the 
  

   western 
  part 
  of 
  this 
  basin, 
  between 
  the 
  100 
  spring 
  plain 
  and 
  

   the 
  Gibbon 
  river. 
  The 
  deposits 
  of 
  siliceous 
  sinter 
  so 
  abundant 
  

   elsewhere 
  in 
  the 
  basin 
  are 
  here 
  quite 
  scanty 
  and 
  form 
  a 
  thin 
  

   coating 
  upon 
  rock 
  composed 
  of 
  small 
  angular 
  fragments 
  of 
  

   pearlite, 
  obsidian, 
  and 
  other 
  forms 
  of 
  rhyolite 
  — 
  generally 
  more 
  

   or 
  less 
  decomposed 
  and 
  mixed 
  with 
  quartz 
  grains, 
  the. 
  whole 
  

   compactly 
  cemented 
  by 
  silica 
  deposited 
  by 
  the 
  hot 
  spring 
  

   waters. 
  Several 
  small 
  outflows 
  of 
  clear 
  and 
  hot 
  acid 
  water 
  

   issue 
  from 
  this 
  cement 
  rock, 
  their 
  united 
  overflow 
  forming 
  a 
  

   small 
  stream 
  which 
  flows 
  through 
  a 
  shallow 
  gutter 
  in 
  the 
  rock 
  

   and 
  joins 
  the 
  Gibbon 
  river 
  a 
  few 
  hundred 
  yards 
  beyond. 
  JSTear 
  

   the 
  vents 
  the 
  channels 
  are 
  lined 
  with 
  an 
  incoherent 
  deposit 
  of 
  

   milky 
  sulphur 
  which 
  frequently 
  coats 
  and 
  obscures 
  a 
  growth 
  

   of 
  algce. 
  The 
  gray 
  surface 
  of 
  the 
  rock 
  shows 
  no 
  trace 
  of 
  the 
  

   brilliantly 
  colored 
  arsenical 
  sulphides, 
  and 
  it 
  is 
  only 
  upon 
  

   breaking 
  this 
  rock 
  about 
  the 
  vents 
  and 
  prying 
  up 
  the 
  plates 
  at 
  

   the 
  margins 
  of 
  the 
  channels 
  that 
  the 
  realgar 
  and 
  orpiment 
  are 
  

   noticed. 
  Plates 
  of 
  rock 
  thus 
  obtained 
  show 
  a 
  brilliant 
  red 
  and 
  

   yellow 
  surface 
  of 
  the 
  mixed 
  sulphides 
  and 
  large 
  pieces 
  of 
  rock 
  

   from 
  about 
  the 
  vents 
  are 
  penetrated 
  and 
  filled 
  with 
  deposits 
  of 
  

   the 
  yellow 
  orpiments, 
  the 
  dark 
  red 
  realgar, 
  and 
  the 
  mixture 
  of 
  

   the 
  two. 
  Many 
  of 
  the 
  specimens 
  show 
  layers 
  of 
  waxy 
  dark 
  

   red 
  translucent 
  realgar 
  an 
  eighth 
  of 
  an 
  inch 
  thick, 
  covered 
  by 
  

   incoherent 
  amorphous 
  orpiment 
  and 
  alternating 
  layers 
  often 
  

   occur. 
  The 
  orpiment 
  generally 
  possesses 
  a 
  tangled 
  filamentous 
  

   structure 
  upon 
  the 
  surfaces 
  of 
  the 
  plates 
  as 
  if 
  deposited 
  upon 
  

   algse 
  threads, 
  and 
  where 
  the 
  surface 
  of 
  the 
  plate 
  is 
  covered 
  

   with 
  realgar 
  as 
  is 
  frequently 
  the 
  case, 
  it 
  too 
  possesses 
  this 
  

   curious 
  form, 
  the 
  mineral 
  being 
  in 
  stalagmitic 
  aggregates 
  with 
  

   a 
  general 
  fibrous 
  matted 
  structure. 
  

  

  In 
  the 
  channels 
  the 
  rocks 
  show 
  no 
  surface 
  coloring 
  from 
  the 
  

   deposition 
  of 
  the 
  sulphides 
  but 
  many 
  small 
  pebble-like 
  masses 
  

   occur, 
  lying 
  in 
  the 
  bottom 
  of 
  the 
  stream, 
  which 
  consist 
  almost 
  

   entirely 
  of 
  dark 
  red 
  translucent 
  realgar. 
  This 
  appears 
  to 
  be 
  

   the 
  most 
  promising 
  material 
  collected 
  for 
  mineral 
  ogical 
  exami- 
  

   nation, 
  but 
  unfortunately 
  none 
  of 
  the 
  specimens 
  proved 
  to 
  con- 
  

   tain 
  any 
  crystals 
  which 
  could 
  be 
  measured 
  and 
  identified 
  under 
  

   the 
  microscope 
  it 
  proved 
  to 
  be 
  in 
  rounded 
  stalagmitic 
  growths 
  

   consisting 
  of 
  a 
  confused 
  crystalline 
  aggregate. 
  Such 
  light 
  

   reflecting 
  surfaces 
  as 
  were 
  seen 
  proved 
  to 
  be 
  small 
  cleavage 
  

   planes. 
  In 
  the 
  closed 
  tube 
  the 
  substance 
  melts 
  and 
  then 
  forms 
  

  

  