﻿256 
  Clarke 
  and 
  Steiger 
  — 
  Experiments 
  nyuh 
  Pectolite, 
  etc. 
  

  

  mixture 
  of 
  ortho- 
  and 
  trisilicate, 
  then 
  all 
  of 
  the 
  analyses 
  

   become 
  intelligible. 
  In 
  most 
  cases 
  the 
  two 
  salts 
  are 
  commin- 
  

   gled 
  in 
  the 
  normal 
  ratio 
  of 
  one 
  to 
  one 
  ; 
  but 
  in 
  our 
  analcite 
  the 
  

   trisilicate 
  predominates, 
  while 
  in 
  some 
  other 
  samples 
  the 
  ortho- 
  

   salt 
  is 
  in 
  excess. 
  All 
  reduce 
  alike 
  to 
  the 
  simple 
  expression 
  

  

  NaAlX. 
  H^O, 
  

  

  in 
  which 
  X 
  represents 
  nSiO^-fmSigOg 
  ; 
  a 
  formula 
  which 
  agrees 
  

   with 
  evidence 
  from 
  various 
  other 
  sources. 
  

  

  For 
  example, 
  analcite 
  may 
  be 
  derived 
  in 
  nature 
  either 
  from 
  

   albite, 
  AlNaSigOg, 
  or 
  nephelite, 
  AlNaSiO^, 
  and 
  on 
  the 
  other 
  

   hand 
  alterations 
  of 
  it 
  into 
  feldspars 
  have 
  been 
  observed. 
  Its 
  

   closest 
  analogue, 
  leucite, 
  has 
  yielded 
  pseudomorphs 
  of 
  ortho- 
  

   clase 
  and 
  elseolite; 
  while 
  leucite 
  and 
  analcite 
  are 
  mutually 
  

   convertible 
  each 
  into 
  the 
  other. 
  The 
  evidence 
  of 
  this 
  charac- 
  

   ter, 
  the 
  evidence 
  of 
  relationship 
  between 
  analcite 
  and 
  other 
  

   species, 
  is 
  varied 
  and 
  abundant 
  ; 
  and 
  the 
  simplest 
  conclusion 
  

   to 
  be 
  drawn 
  from 
  it 
  is 
  that 
  which 
  has 
  been 
  given. 
  Every 
  

   alteration, 
  every 
  derivation, 
  every 
  variation 
  in 
  the 
  composition 
  

   of 
  analcite, 
  points 
  to 
  the 
  same 
  belief. 
  The 
  consistency 
  of 
  the 
  

   data 
  cannot 
  well 
  be 
  denied. 
  

  

  In 
  the 
  case 
  of 
  a 
  normal 
  analcite, 
  that 
  is, 
  one 
  which 
  conforms 
  

   to 
  the 
  usual 
  empirical 
  formula, 
  the 
  expression 
  which 
  best 
  

   represents 
  these 
  relations 
  is 
  

  

  Al.Na,(SiO.), 
  (SiA),.4H,0; 
  

  

  and 
  this 
  accords 
  with 
  the 
  minimum 
  molecular 
  weight 
  as 
  de- 
  

   termined 
  by 
  the 
  study 
  of 
  our 
  ammoniated 
  residue. 
  Struc- 
  

   turally, 
  this 
  is 
  comparable 
  with 
  the 
  formulae 
  of 
  garnet, 
  zunyite, 
  

   sodalite, 
  nosite 
  and 
  leucite 
  ; 
  all 
  of 
  which 
  are 
  also 
  isometric 
  in 
  

   crystallization. 
  The 
  more 
  important 
  of 
  the 
  symbols 
  are 
  as 
  

   follows 
  : 
  

  

  SiO,= 
  Ca 
  SiO,=Na, 
  SiO,=Na, 
  

  

  / 
  \Ca 
  / 
  \a1-C1 
  / 
  \Al-SO,-Na 
  

  

  Al 
  SiO, 
  = 
  Ca 
  Al 
  SiO,=:Na, 
  Al 
  SiO, 
  = 
  Na, 
  

  

  \ 
  \ 
  \ 
  

  

  SiO, 
  = 
  Al 
  SiO^^Al 
  SiO, 
  = 
  Al 
  

  

  Garnet. 
  Sodalite. 
  Nosite. 
  

  

  SiO 
  =K, 
  SiO,=Na, 
  

   / 
  \Al-SiO, 
  = 
  Al. 
  / 
  \Al-SiO,=Al. 
  

   Al 
  Si30,=K, 
  Al 
  Si30^=Na, 
  +4H,0. 
  

  

  Si30^^Al 
  Si30, 
  = 
  Al 
  

  

  Leucite. 
  Analcite. 
  

  

  