﻿BARREN 
  ISLAND. 
  19 
  

  

  found 
  to 
  redden 
  litmus 
  paper 
  immediately, 
  while 
  they 
  had 
  no 
  action 
  

   on 
  acetate 
  of 
  lead 
  paper. 
  The 
  surfaces 
  of 
  the 
  rock 
  near 
  the 
  vents 
  were 
  

   covered 
  with 
  a 
  white 
  vesicular 
  stalactitic 
  substance, 
  and 
  with 
  a 
  red 
  and 
  

   orange 
  deliquescent 
  matter. 
  The 
  former 
  was 
  found 
  to 
  consist 
  mainly 
  of 
  

   a 
  basic 
  sulphate 
  of 
  alumina, 
  with 
  a 
  little 
  calcium 
  chloride, 
  while 
  the 
  red 
  

   incrustation 
  consisted 
  of 
  calcium 
  chloride, 
  with 
  basic 
  sulphate 
  of 
  alumina 
  

   and 
  ferric 
  oxide. 
  1 
  Fibrous 
  gypsum 
  also 
  occurs 
  along 
  with 
  the 
  other 
  

   products 
  of 
  alteration. 
  

  

  There 
  is 
  another 
  smaller 
  solfatara 
  to 
  the 
  north-east 
  of 
  the 
  above 
  

   extending 
  from 
  the 
  edge 
  of 
  the 
  crater 
  down 
  the 
  outward 
  slope, 
  with 
  an 
  

   area 
  of 
  about 
  30 
  feet 
  X 
  20. 
  There 
  was 
  a 
  similar 
  crust 
  of 
  sulphur, 
  with 
  

   bleached 
  ash 
  beneath 
  : 
  in 
  this, 
  at 
  a 
  depth 
  of 
  7 
  feet, 
  a 
  mass 
  of 
  pasty 
  white 
  

   matter 
  was 
  come 
  upon 
  (like 
  the 
  ash 
  around 
  it, 
  so 
  hot 
  that 
  it 
  could 
  not 
  be 
  

   touched), 
  specimens 
  of 
  which 
  dried 
  into 
  a 
  mealy 
  substance 
  like 
  kaolin, 
  

   but 
  which 
  were 
  found 
  to 
  consist 
  of 
  a 
  basic 
  sulphate 
  of 
  alumina 
  with 
  a 
  

   little 
  potash 
  and 
  lime. 
  To 
  the 
  south 
  of 
  the 
  crater 
  bottom 
  there 
  is 
  a 
  third 
  

   solfatara, 
  from 
  which 
  steam 
  issues 
  here 
  and 
  there 
  j 
  and 
  in 
  some 
  other 
  

   spots 
  about 
  the 
  crater 
  sulphur 
  occurs 
  in 
  a 
  similar 
  way, 
  but 
  in 
  smaller 
  

   quantity. 
  

  

  The 
  oldest 
  visible 
  lava 
  in 
  connection 
  with 
  the 
  central 
  cone 
  is 
  probably 
  

   Lavas 
  of 
  the 
  central 
  that 
  which 
  forms 
  a 
  slight 
  hummock 
  on 
  the 
  north- 
  

   cone 
  * 
  western 
  slope, 
  some 
  250 
  feet 
  below 
  the 
  crater. 
  

  

  The 
  stream 
  which 
  doubtless 
  flowed 
  down 
  from 
  this 
  point 
  has 
  disappeared, 
  

   partly 
  through 
  the 
  lava 
  having 
  disintegrated, 
  and 
  rolled 
  to 
  the 
  bottom 
  of 
  

   the 
  cone, 
  and 
  in 
  part 
  probably 
  through 
  its 
  having 
  been 
  covered 
  over 
  by 
  

   scoriae, 
  &c. 
  The 
  lava 
  inside 
  the 
  crater 
  has 
  already 
  been 
  mentioned. 
  Of 
  

   what 
  may 
  be 
  called 
  quite 
  recent 
  lava 
  there 
  are 
  three 
  distinct 
  flows, 
  which 
  

   may 
  be 
  distinguished 
  as 
  the 
  eastern, 
  the 
  southern, 
  and 
  the 
  northern 
  

  

  1 
  The 
  occurrence 
  of 
  native 
  calcium 
  chloride 
  is 
  of 
  some 
  interest,, 
  as 
  it 
  is 
  a 
  mitt 
  ral 
  which 
  

   has 
  not 
  been 
  often 
  found 
  hitherto. 
  It 
  - 
  has, 
  however, 
  been 
  observed 
  at 
  some 
  of 
  the 
  

   fumaroles 
  of 
  Hekla, 
  and 
  was 
  noticed 
  amongst 
  the 
  sublimates 
  produced 
  during 
  the 
  Vesuvian 
  

   eruption 
  of 
  1872, 
  by 
  Palmieri. 
  It 
  has 
  been 
  given 
  the 
  mineralogical 
  name 
  of 
  chlorocalcite. 
  

   There 
  is 
  a 
  specimen, 
  from 
  Vesuvius, 
  in 
  the 
  Museum 
  at 
  Bonn, 
  consisting 
  of 
  small 
  white 
  

   isometric 
  crystals 
  hermetically 
  sealed 
  in 
  a 
  glass 
  tube. 
  

  

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