﻿liadioactivity 
  of 
  certain 
  Lavas. 
  581 
  

  

  The 
  table 
  here 
  given 
  embodies 
  the 
  experiments 
  on 
  lavas 
  *. 
  

   It 
  first 
  deals 
  with 
  materials 
  from 
  the 
  Vesuvian 
  focus 
  of 
  

   eruption. 
  Lavas 
  ejected 
  from 
  the 
  neighbouring 
  petro- 
  

   graphical 
  provinces 
  are 
  given 
  next. 
  A 
  few 
  results 
  from 
  

   widely 
  distributed 
  volcanoes 
  are 
  added 
  for 
  comparison. 
  

   This 
  last 
  list 
  is, 
  I 
  am 
  aware, 
  too 
  short, 
  the 
  subject 
  being^ 
  

   deserving 
  of 
  fuller 
  treatment. 
  Finally, 
  some 
  separated 
  rock 
  

   minerals 
  from 
  \^esuvius 
  are 
  dealt 
  with. 
  It 
  may 
  at 
  once 
  be 
  

   pointed 
  out 
  that 
  there 
  is 
  evidently 
  no 
  concentration 
  of 
  radium 
  

   in 
  these 
  minerals. 
  The 
  radium 
  is 
  apparently 
  distributed 
  

   throughout 
  the 
  magma. 
  In 
  the 
  table 
  a 
  query 
  after 
  a 
  deter- 
  

   mination 
  denotes 
  the 
  presence 
  of 
  some 
  precipitate 
  in 
  the 
  acid 
  

   solution. 
  

  

  Eadium 
  Thorium 
  

  

  xio-i^. 
  xio-^ 
  

  

  Monte 
  Somma 
  ; 
  very 
  old 
  dyke 
  2*8 
  2*2 
  

  

  Vesuvius, 
  1631 
  ; 
  Gravina 
  7-8 
  1-7 
  

  

  1794; 
  Torre 
  del 
  Greco 
  9*8 
  0-6 
  

  

  1832 
  13*0 
  2*3 
  

  

  1855 
  ;* 
  LeNoveVleT 
  (i2'5)r(i2-^^^ 
  125 
  2-5 
  

  

  1868; 
  (11-9), 
  (13-3) 
  12-6 
  41 
  

  

  „ 
  1895-99 
  ; 
  Colle 
  Umberto 
  ; 
  slow 
  out-flow 
  ; 
  

  

  (15-3), 
  (14-0) 
  14-6 
  2-1 
  

  

  „ 
  1906 
  ; 
  Torre 
  Aununziata 
  ; 
  interior 
  of 
  lava 
  

  

  stream 
  ; 
  (17-9), 
  (14-2) 
  (?) 
  16-0 
  2-6 
  

  

  „ 
  1906; 
  Glassy 
  lava; 
  cooled 
  in 
  cistern 
  13*8 
  

  

  1906 
  ; 
  Flotation 
  bomb, 
  Boscotrecase 
  107 
  (?) 
  

  

  „ 
  1906 
  ; 
  Ejected 
  old 
  lava 
  block 
  with 
  tachylite 
  

  

  filling 
  9-2 
  

  

  Campi 
  Phlegraei, 
  Monte 
  Olibano 
  ; 
  trachyte 
  ; 
  (78). 
  

  

  {b-S) 
  6-8 
  4-2 
  

  

  Ischia 
  ; 
  olivine 
  trachyte 
  ; 
  (4-3), 
  (7*8) 
  G'O 
  2'4 
  

  

  Lipari, 
  Eocchi 
  Rossi 
  ; 
  lava; 
  (5"8), 
  (4'6) 
  5*2 
  4*5 
  

  

  ,, 
  Val 
  di 
  Lachi 
  ; 
  augite 
  andesite 
  1'6 
  0"5 
  

  

  Stromboli, 
  scoria 
  ; 
  (3*9), 
  (3*2) 
  3*5 
  1*5 
  

  

  Vulcano 
  ; 
  bomb 
  ; 
  (5-3), 
  (4-6) 
  bO 
  4*6 
  

  

  Etna, 
  Val 
  del 
  Bove 
  ; 
  1855 
  ; 
  lava 
  6-0 
  1-2 
  

  

  Pantellaria, 
  La 
  Mantua 
  ; 
  lava.., 
  3"1 
  2"2 
  

  

  Kilauea, 
  crater, 
  1875 
  ; 
  lava 
  39 
  1*4 
  

  

  Ascension 
  Island 
  ; 
  obsidian 
  1*6 
  2*5 
  

  

  Krakatao, 
  ash 
  ; 
  collected 
  about 
  17 
  miles 
  N.E. 
  of 
  

  

  volcano: 
  1883 
  0-6 
  

  

  pumice; 
  1883 
  4-5 
  5*2 
  

  

  Chimborazo, 
  near 
  Quito 
  ; 
  pumice 
  3*2 
  2-4 
  

  

  St. 
  Helena; 
  lava 
  2-3 
  (?) 
  0-6 
  

  

  Martinique; 
  bomb, 
  much 
  weathered 
  1'3 
  

  

  Iceland; 
  lava 
  1'5(?) 
  

  

  Vesuvius; 
  cube 
  of 
  halite 
  with 
  pui'ple 
  streaks 
  00 
  

  

  leucite 
  I'O 
  06 
  

  

  biotite 
  2-6 
  

  

  * 
  Some 
  of 
  the 
  results 
  have 
  appeared 
  in 
  " 
  Radioactivity 
  and 
  Geology," 
  

   p. 
  43. 
  As 
  therein 
  given 
  they 
  are 
  unfortunately 
  affected 
  by 
  an 
  error 
  which 
  

   arose 
  in 
  calculating 
  the 
  constant 
  of 
  a 
  recently 
  constructed 
  electroscope. 
  

  

  