﻿144 
  Yander 
  Meule/i 
  — 
  Two 
  So-called 
  Hcdloy 
  sites. 
  

  

  A 
  comparison 
  of 
  these 
  curves 
  is 
  interesting. 
  The 
  Chattooga 
  

   clay, 
  which 
  contains 
  approximately 
  21 
  per 
  cent 
  of 
  hydrargillite, 
  

   probably 
  in 
  a 
  colloidal 
  form, 
  lost 
  about 
  six 
  per 
  cent 
  of 
  water 
  

   below 
  300°. 
  The 
  bulk 
  of 
  the 
  water 
  was 
  'removed 
  between 
  

   450° 
  and 
  500°. 
  This 
  amount 
  of 
  water 
  would 
  be 
  lost 
  if 
  the 
  

   hydrargillite 
  gave 
  up 
  most 
  of 
  the 
  water 
  combined 
  with 
  it, 
  below 
  

   300°. 
  The 
  water 
  remaining 
  combined 
  with 
  the 
  alumina 
  

   appears 
  to 
  be 
  removed 
  at 
  the 
  temperature 
  at 
  which 
  most 
  of 
  the 
  

   water 
  is 
  removed 
  from 
  the 
  kaolinite, 
  between 
  450° 
  and 
  500°. 
  

   The 
  Alabama 
  clay, 
  which 
  contains 
  only 
  about 
  five 
  per 
  cent 
  of 
  

   hydrargillite, 
  also 
  loses 
  a 
  small 
  amount 
  of 
  water 
  below 
  300°, 
  

   after 
  which 
  the 
  bulk 
  is 
  again 
  given 
  off 
  between 
  450° 
  and 
  500° 
  . 
  

   In 
  both 
  cases 
  the 
  last 
  traces 
  are 
  removed 
  only 
  above 
  900°. 
  

  

  Conclusions. 
  

  

  The 
  chemical 
  analysis 
  of 
  the 
  two 
  clays 
  shows 
  that 
  they 
  con- 
  

   tain 
  less 
  water 
  and 
  more 
  alumina, 
  and 
  to 
  have 
  a 
  higher 
  specific 
  

   gravity 
  than 
  halloysite. 
  They 
  may 
  be 
  regarded 
  as 
  mixtures 
  of 
  

   kaolinite 
  and 
  hydrargillite, 
  with 
  smaller 
  amounts 
  of 
  other 
  sub- 
  

   stances. 
  

  

  It 
  also 
  points 
  to 
  the 
  fact 
  already 
  emphasized 
  by 
  others, 
  that 
  

   some 
  of 
  the 
  high 
  alumina 
  clays, 
  instead 
  of 
  being 
  composed 
  

   chiefly 
  of 
  some 
  hydrous 
  aluminium 
  silicate 
  other 
  than 
  kaolinite, 
  

   are 
  probably 
  in 
  many 
  cases 
  mixtures 
  of 
  kaolinite 
  and 
  some 
  

   aluminium 
  hydrate, 
  like 
  hydrargillite. 
  

  

  Under 
  the 
  conditions 
  of 
  the 
  experiments, 
  digestion 
  with 
  

   dilute 
  snlphuric 
  acid 
  for 
  the 
  purpose 
  of 
  determining 
  the 
  con- 
  

   stituents 
  of 
  a 
  clay 
  mixture 
  is 
  of 
  doubtful 
  value. 
  

  

  Dehydration 
  of 
  a 
  clay 
  mixture 
  containing 
  hydrargillite 
  tends 
  

   to 
  remove 
  most 
  of 
  the 
  water 
  of 
  the 
  hydrargillite 
  below 
  300°; 
  

   the 
  remainder 
  is 
  driven 
  off 
  along 
  with 
  the 
  chemically 
  combined 
  

   water 
  of 
  the 
  kaolinite 
  between 
  450° 
  and 
  500.° 
  The 
  last 
  traces 
  

   of 
  water 
  are 
  removed 
  only 
  above 
  900.° 
  

  

  A 
  crystalline 
  substance 
  in 
  the 
  Chattooga 
  clav 
  was 
  shown 
  to 
  

   be 
  exceptionally 
  well 
  crystallized 
  hydrargillite, 
  and 
  its 
  indices 
  of 
  

   refraction 
  were 
  found 
  to 
  be 
  slightly 
  higher 
  than 
  those 
  usually 
  

   given 
  for 
  this 
  substance. 
  

  

  Mineralogicnl 
  Laboratory, 
  

   Cornell 
  University. 
  

  

  