﻿294 
  Washington 
  — 
  Analyses 
  of 
  Italian 
  Volcanic 
  Eoclcs. 
  

  

  bnscli" 
  lias 
  pointed 
  out 
  tlie 
  close 
  ]*esemblance 
  between 
  the 
  

   pantellerites 
  of 
  Pantelleria 
  and 
  the 
  commendites 
  of 
  San 
  Pietro 
  

   on 
  the 
  southwest 
  coast 
  of 
  Sardinia, 
  which, 
  as 
  well 
  as 
  the 
  other 
  

   rocks 
  of 
  Pantelleria, 
  are 
  high 
  in 
  Na^O.f 
  At 
  the 
  volcano 
  of 
  

   Monte 
  Ferruij; 
  in 
  Sardinia 
  Doelter 
  found 
  the 
  rocks 
  to 
  be 
  tra- 
  

   chytes, 
  phonolites 
  and 
  basalts 
  (with 
  some 
  leucite-basalts), 
  which, 
  

   according 
  to 
  his 
  analyses, 
  show 
  Na^O 
  (molecularly) 
  unifornaly 
  

   higher 
  than 
  K^O, 
  and 
  in 
  some 
  cases 
  verj^ 
  high. 
  

  

  It 
  would 
  seem, 
  then, 
  from 
  these 
  rather 
  insufficient 
  and 
  sum- 
  

   marily 
  given 
  facts, 
  that 
  we 
  have 
  in 
  the 
  Italian 
  district 
  three 
  

   parallel 
  volcanic 
  lines. 
  The 
  latest, 
  along 
  the 
  peninsula, 
  is 
  

   characterized 
  chiefly 
  by 
  high 
  K^O, 
  as 
  well 
  as 
  high 
  CaO, 
  and 
  by 
  

   the 
  presence 
  of 
  leucite. 
  The 
  next, 
  that 
  of 
  the 
  islands 
  along 
  

   the 
  west 
  coast, 
  is 
  also 
  high 
  in 
  alkalies 
  but 
  with 
  Na^O 
  rather 
  

   higher 
  than 
  K2O, 
  and 
  without 
  leucite. 
  The 
  third, 
  wdiich 
  lies 
  

   far 
  out 
  in 
  the 
  Mediterranean, 
  and 
  which 
  is 
  possibly 
  the 
  oldest, 
  

   is 
  much 
  higher 
  in 
  Na^O 
  and 
  seems 
  to 
  be 
  characterized 
  by 
  the 
  

   presence 
  of 
  peculiar 
  soda 
  minerals, 
  such 
  as 
  aenigmatite 
  and 
  

   segirine, 
  nepheline 
  also 
  occurring 
  in 
  places. 
  The 
  relations 
  of 
  

   the 
  three 
  main 
  centers 
  exterior 
  to 
  these 
  lines, 
  those 
  of 
  the 
  

   Euganean 
  and 
  Berici 
  Hills 
  and 
  Monte 
  Vulture, 
  are 
  uncertain 
  

   and 
  need 
  not 
  be 
  discussed 
  here. 
  

  

  Aug. 
  1, 
  1899. 
  

  

  *RoseDbusch, 
  Mikr. 
  Phys., 
  ii, 
  1896, 
  p. 
  614. 
  

  

  f 
  We 
  cannot 
  determine 
  this 
  point 
  in 
  regard 
  to 
  the 
  other 
  rocks 
  of 
  San 
  Pietro. 
  as 
  

   Eigel 
  (Min. 
  Petr. 
  Mitth., 
  vhi, 
  p. 
  73, 
  1886) 
  unfortunately 
  did 
  not 
  determine 
  the 
  alka- 
  

   lies 
  separately. 
  

  

  X 
  Doelter, 
  Abh. 
  Akad. 
  Wiss. 
  Wien., 
  xxxviii, 
  p. 
  41, 
  1878. 
  

  

  