﻿12 
  Brackett 
  and 
  Williams 
  — 
  Newtonite 
  and 
  Rectorite. 
  

  

  Al^-SiO=H„ 
  

   ^SiO=Al. 
  

  

  Either 
  of 
  these 
  formulas 
  suggests 
  the 
  possibility 
  of 
  the 
  exist- 
  

   ence 
  of 
  other 
  hydrous 
  silicates 
  of 
  alumina 
  closely 
  related 
  to 
  

   kaolinite, 
  and 
  indeed 
  differing 
  from 
  it 
  only 
  in 
  the 
  presence 
  of 
  

   a 
  larger 
  or 
  smaller 
  proportion 
  of 
  water, 
  while 
  the 
  relation 
  of 
  

   the 
  silica 
  to 
  the 
  alumina 
  remains 
  constant. 
  

  

  It 
  is 
  readily 
  seen 
  that 
  three 
  other 
  hydrous 
  silicates 
  of 
  

   alumina 
  may 
  be 
  derived 
  by 
  eliminating 
  one 
  molecule, 
  or 
  intro- 
  

   ducing 
  respectively 
  one 
  and 
  two 
  molecules 
  of 
  water 
  into 
  the 
  

   formula, 
  and 
  that 
  thus 
  the 
  following 
  series 
  would 
  be 
  formed 
  : 
  

  

  Formulas. 
  Percentage 
  composition. 
  

  

  A1 
  2 
  3 
  Si0 
  2 
  H 
  2 
  

  

  2Si0 
  2 
  . 
  H 
  2 
  42*52 
  49'99 
  7*49 
  

  

  2Si0 
  2 
  . 
  2H 
  2 
  39*57 
  46'50 
  13*93 
  

  

  2Si0 
  2 
  .3H 
  2 
  36-98 
  43'47 
  19'55 
  

  

  2Si0 
  2 
  . 
  4H 
  2 
  34-72 
  40'82 
  24*46 
  

  

  Of 
  this 
  series 
  of 
  four 
  theoretically 
  possible 
  hydrous 
  silicates 
  

   of 
  alumina 
  only 
  one, 
  No. 
  2 
  of 
  the 
  series, 
  ordinary 
  kaolin, 
  has 
  

   been 
  described, 
  so 
  far 
  as 
  we 
  have 
  been 
  able 
  to 
  find 
  in 
  the 
  lit- 
  

   erature 
  at 
  our 
  command. 
  From 
  many 
  of 
  the 
  published 
  analyses 
  

   of 
  halloysite, 
  this 
  mineral 
  might 
  be 
  supposed 
  to 
  correspond 
  

   with 
  No. 
  4 
  of 
  the 
  series, 
  but, 
  as 
  will 
  be 
  shown 
  below, 
  this 
  cor- 
  

   respondence 
  is 
  only 
  apparent. 
  

  

  This 
  series 
  will 
  be 
  designated 
  as 
  the 
  Kaolinite 
  Series* 
  and 
  

   will 
  include 
  the 
  Kaolinite 
  Group, 
  which 
  was 
  first 
  established 
  

   by 
  J. 
  D. 
  Dana 
  in 
  1858 
  f 
  under 
  the 
  name 
  of 
  the 
  Halloysite 
  

   Group, 
  but 
  was 
  afterwards 
  called 
  the 
  Kaolinite 
  Group 
  by 
  the 
  

   same 
  author.^ 
  The 
  object 
  of 
  forming 
  such 
  a 
  series 
  is 
  to 
  classify 
  

   if 
  possible 
  the 
  already 
  existing 
  members 
  of 
  the 
  kaolinite 
  group, 
  

   most, 
  if 
  not 
  all 
  of 
  which 
  will 
  be 
  found 
  to 
  fall 
  under 
  kaolinite 
  ; 
  

   and 
  at 
  the 
  same 
  time 
  to 
  have 
  a 
  definite 
  place 
  into 
  which 
  to 
  put 
  

   any 
  new 
  minerals 
  of 
  this 
  class 
  which, 
  like 
  rectorite 
  and 
  newton- 
  

   ite, 
  may 
  from 
  time 
  to 
  time 
  be 
  found, 
  and 
  which 
  would 
  at 
  

   present 
  hardly 
  be 
  classed 
  under 
  kaolinite 
  itself 
  if 
  their 
  water 
  

   of 
  constitution 
  was 
  properly 
  determined. 
  It 
  is 
  the 
  hope 
  of 
  the 
  

   authors 
  to 
  be 
  able 
  in 
  a 
  future 
  paper 
  to 
  show 
  the 
  true 
  chemical 
  

   composition 
  and 
  microscopic 
  structure 
  of 
  many 
  minerals 
  now 
  

   existing 
  as 
  members 
  of 
  the 
  kaolinite 
  group 
  ; 
  and 
  to 
  assign 
  them 
  

   to 
  their 
  proper 
  place 
  in 
  the 
  above-mentioned 
  series, 
  by 
  rede- 
  

  

  * 
  The 
  word 
  series 
  is 
  not 
  used 
  here 
  in 
  the 
  sense 
  in 
  which 
  it 
  is 
  geuerally 
  applied 
  

   in 
  the 
  natural 
  sciences, 
  but 
  as 
  it 
  is 
  employed 
  in 
  mathematics 
  to 
  describe 
  a 
  se- 
  

   quence 
  of 
  similar 
  terms 
  which 
  bear 
  some 
  definite 
  relation 
  to 
  each 
  other. 
  

  

  + 
  This 
  Journal, 
  II, 
  vol. 
  xxvi, 
  p. 
  36!, 
  1858. 
  

  

  X 
  System 
  of 
  Mineralogy, 
  J. 
  D. 
  Dana, 
  5th 
  edition, 
  1868. 
  

  

  