﻿Brackett 
  and 
  Williams 
  — 
  JVewtonite 
  and 
  Rectorite. 
  11 
  

  

  solution, 
  including 
  the 
  eccentricity 
  of 
  the 
  center 
  of 
  polarization, 
  

   the 
  inclination 
  of 
  the 
  axis 
  of 
  polarization 
  to 
  the 
  plane 
  of 
  

   reference, 
  besides 
  such 
  corrections 
  as 
  may 
  arise 
  from 
  refraction, 
  

   or 
  diffraction 
  or 
  photography. 
  The 
  importance 
  of 
  the 
  problem 
  

   will 
  certainly 
  justify 
  us 
  in 
  trying 
  to 
  take 
  good 
  photographs 
  of 
  

   the 
  streamers 
  at 
  the 
  future 
  eclipses. 
  

  

  Art. 
  II. 
  — 
  Newtonite 
  and 
  Rectorite 
  — 
  two 
  new 
  mine 
  r 
  rals 
  of 
  

   the 
  Kaolinite 
  Group 
  ; 
  by 
  R. 
  N. 
  Brackett 
  and 
  J. 
  Francis 
  

   Williams. 
  

  

  [Published 
  by 
  permission 
  of 
  the 
  State 
  Geologist 
  of 
  Arkansas.] 
  

  

  The 
  object 
  of 
  the 
  following 
  paper 
  is 
  to 
  briefly 
  describe 
  two 
  

   hydrous 
  silicates 
  of 
  alumina, 
  which 
  we 
  have 
  every 
  reason 
  to 
  

   believe 
  have 
  not 
  before 
  been 
  observed, 
  and 
  to 
  call 
  attention 
  to 
  

   the 
  relation 
  of 
  these 
  new 
  compounds 
  to 
  other 
  members 
  of 
  the 
  

   group. 
  

  

  As 
  is 
  well 
  known 
  and 
  generally 
  admitted 
  the 
  commonest 
  

   substance 
  of 
  this 
  class, 
  kaolin, 
  or 
  when 
  crystallized 
  called 
  

   kaolinite, 
  approaches 
  the 
  composition 
  represented 
  by 
  the 
  for- 
  

   mula 
  A1 
  2 
  8 
  . 
  2Si0 
  2 
  . 
  2H 
  2 
  0, 
  and 
  has 
  the 
  percentage 
  composition 
  : 
  

  

  Si0 
  2 
  46-50 
  A1 
  2 
  3 
  39-57 
  H 
  2 
  13-93 
  =: 
  100. 
  

  

  Considering 
  half 
  of 
  the 
  water 
  basic 
  or 
  as 
  water 
  of 
  constitu- 
  

   tion 
  and 
  dividing 
  the 
  formula 
  by 
  two, 
  the 
  constitution 
  of 
  kao- 
  

   linite 
  may 
  be 
  represented 
  as 
  follows 
  :* 
  

  

  Si— 
  0\ 
  

  

  ^-o— 
  Ammo). 
  

  

  As 
  there 
  is 
  reason 
  to 
  think 
  that 
  all 
  the 
  water 
  represented 
  in 
  

   the 
  original 
  formula 
  should 
  be 
  regarded 
  as 
  water 
  of 
  constitu- 
  

   tion, 
  the 
  formula 
  would 
  become 
  : 
  

  

  ^OH 
  HCK 
  

  

  Si— 
  OH 
  HO— 
  Si, 
  

  

  x 
  O— 
  -Al— 
  O— 
  Al— 
  cr 
  

  

  or 
  writing 
  this 
  in 
  the 
  form 
  suggested 
  by 
  F. 
  W. 
  Clarke 
  in 
  his 
  

   paper 
  on 
  the 
  Structure 
  of 
  the 
  Natural 
  Silicates, 
  f 
  the 
  following 
  

   formula 
  is 
  obtained 
  : 
  

  

  * 
  Kaolinite 
  is 
  thus 
  regarded 
  as 
  a 
  derivative 
  of 
  normal 
  silicic 
  acid 
  Si(OH) 
  4 
  , 
  anal- 
  

   ogous 
  to 
  a 
  similar 
  compound 
  A,1 
  2 
  3 
  . 
  2Si0 
  2 
  . 
  HH 
  2 
  mentioned 
  by 
  Remsen. 
  Inor- 
  

   ganic 
  Chemistry 
  by 
  Ira 
  Eemsen. 
  American 
  Science 
  Series 
  — 
  Advanced 
  Course. 
  

   New 
  York: 
  Henry 
  Holt 
  & 
  Company, 
  1889, 
  p. 
  576. 
  

  

  \ 
  Bulletin 
  of 
  the 
  U. 
  S. 
  Geological 
  Survey, 
  No. 
  60. 
  TVashiugton, 
  1890, 
  p. 
  16. 
  

  

  