﻿290 
  Washington 
  — 
  Analyses 
  of 
  Italian 
  Volcanic 
  Bochs. 
  

  

  Analyses 
  of 
  the 
  Arso 
  lava 
  are 
  given 
  below. 
  Mine 
  agrees 
  

   fairly 
  well 
  with 
  that 
  of 
  Fiichs, 
  though 
  there 
  are 
  certain 
  dif- 
  

   ferences, 
  notably 
  in 
  the 
  alkalies. 
  His 
  analysis 
  of 
  the 
  scoria 
  of 
  

   this 
  eruption, 
  from 
  Le 
  Cremate, 
  is 
  lower 
  in 
  SiO^ 
  and 
  higher 
  in 
  

   AI2O3, 
  but 
  otherwise 
  resembles 
  that 
  of 
  the 
  main 
  part 
  of 
  the 
  

   flow. 
  Abich's 
  analysis 
  differs 
  in 
  several 
  particulars 
  from 
  the 
  

   others, 
  and 
  is 
  inserted 
  only 
  for 
  the 
  sake 
  of 
  completeness. 
  

  

  This 
  rock 
  differs 
  markedly 
  from 
  the 
  other 
  trachytes 
  of 
  

   Isshia, 
  which, 
  as 
  Fachs 
  has 
  shown, 
  have 
  a 
  very 
  uniform 
  com- 
  

   position. 
  It 
  is 
  much 
  more 
  basic, 
  showing 
  lower 
  Si02 
  and 
  alka- 
  

   lies, 
  and 
  higher 
  FeO, 
  MgO 
  and 
  CaO. 
  The 
  sections 
  also 
  reveal 
  

  

  I 
  II 
  III 
  IV 
  T 
  

  

  SiO, 
  50-'75 
  57-73 
  54-83 
  61-03 
  57-91 
  

  

  TiO, 
  1-24 
  ._.. 
  0-65 
  

  

  Al.Og 
  18-37 
  17-85 
  20-17 
  17-21 
  15-79 
  

  

  Fe^O^ 
  2-22 
  4-44 
  4-77 
  ) 
  6-81 
  

  

  FeO, 
  3-04 
  3-90 
  3-86 
  \ 
  0-01 
  

  

  MnO 
  .. 
  .. 
  trace 
  0-17 
  0-23 
  

  

  MgO 
  2-02 
  1-77 
  1-93 
  2-07 
  1-66 
  

  

  CaO 
  .. 
  4-68 
  3-65 
  4-12 
  1-43 
  2-99 
  

  

  Na,0 
  4-85 
  3-67 
  3-04 
  4-64 
  601 
  

  

  K,0 
  5-92 
  7-65 
  7-38 
  7*16 
  7-27 
  

  

  H,0 
  0-18 
  0-09 
  0-46 
  0-56 
  0-34 
  

  

  CI... 
  0-11 
  0-60 
  

  

  P^O, 
  trace 
  O-Ol 
  

  

  99-38 
  100-85 
  100-56 
  99-11 
  100-27 
  

  

  = 
  01.-- 
  0-03 
  0-14 
  

  

  99-35 
  10013 
  

  

  I. 
  "Ciminite," 
  Arso, 
  Ischia. 
  H. 
  S. 
  Washington 
  anal. 
  

  

  II. 
  Ditto, 
  Arso. 
  Fuchs 
  anal. 
  Min. 
  Petr. 
  Mitth., 
  1872, 
  p. 
  230. 
  

   HI. 
  Scoria, 
  Le 
  Cremate. 
  Fnchs 
  anal., 
  op. 
  cit., 
  p. 
  231. 
  

  

  IV. 
  "Ciminite," 
  Arso. 
  Abich 
  anal., 
  Yulk. 
  Ersch., 
  1841, 
  p. 
  44. 
  

   Y. 
  Sodalite-Trachyte, 
  Monte 
  Santo, 
  Naples. 
  Johnston-Lavis 
  

   anaL 
  Geol. 
  Mag. 
  (Ill), 
  vi, 
  p. 
  77, 
  1889. 
  

  

  the 
  presence 
  of 
  some 
  olivine 
  and 
  considerable 
  basic 
  labradorite. 
  

   The 
  rock, 
  therefore, 
  is 
  not 
  a 
  typical 
  trachyte, 
  and 
  was 
  placed 
  

   by 
  me 
  among 
  the 
  group 
  of 
  ciminites 
  recently 
  described."^ 
  It, 
  

   however, 
  does 
  not 
  contain 
  as 
  much 
  MgO 
  and 
  CaO 
  as 
  these 
  

   do 
  normally, 
  and 
  might 
  better 
  be 
  considered 
  as 
  transitional 
  

   between 
  them 
  and 
  the 
  normal 
  trachytes. 
  

  

  In 
  a 
  recent 
  paperf 
  Rosenbusch 
  describes 
  the 
  minerals 
  lining 
  

   the 
  crevices 
  of 
  this 
  rock, 
  which 
  include 
  alkali-feldspar, 
  sodalite, 
  

  

  * 
  Jour. 
  Geol, 
  iv, 
  p. 
  834, 
  1896 
  and 
  v, 
  p. 
  351, 
  1897. 
  

  

  f 
  Rosenbusch, 
  Ueber 
  EuAtolitb, 
  etc., 
  Sitz. 
  ber. 
  Akad. 
  Wiss., 
  Berlin. 
  1S99. 
  p. 
  

  

  III, 
  notel. 
  

  

  