﻿26 
  MALLET 
  : 
  VOLCANOES 
  OF 
  BARREN 
  ISLAND 
  AND 
  NARCONDAtf, 
  

  

  Captain 
  Blair's 
  silence 
  respecting 
  the 
  hot 
  spring 
  quite 
  tallies 
  with 
  ths 
  

   supposition 
  that 
  the 
  lava, 
  which 
  he 
  does 
  not 
  mention 
  either, 
  was 
  emitted 
  

   after 
  his 
  visit. 
  1 
  The 
  earliest 
  allusion 
  to 
  the 
  spring 
  is 
  that 
  by 
  the 
  ob- 
  

   server 
  who 
  saw 
  it 
  in 
  1832, 
  when 
  the 
  amount 
  of 
  heat 
  given 
  off 
  (by 
  

   the 
  spring 
  itself, 
  and 
  by 
  the 
  sea 
  in 
  the 
  immediate 
  neighbourhood) 
  seems 
  

   to 
  have 
  been 
  much 
  greater 
  than 
  that 
  noticed 
  by 
  later 
  visitors. 
  The 
  lava 
  

   up 
  to 
  about 
  the 
  year 
  1860, 
  although 
  continually 
  cooling, 
  appears 
  to 
  have 
  

   still 
  retained 
  sufficient 
  heat, 
  at 
  the 
  base 
  of 
  the 
  flow, 
  to 
  maintain 
  the 
  

   spring 
  t 
  at, 
  or 
  near, 
  the 
  boiling 
  point, 
  but 
  during 
  the 
  last 
  quarter 
  of 
  a 
  

   century 
  the 
  further 
  cooling 
  of 
  the 
  rock 
  has 
  resulted 
  in 
  the 
  spring 
  

   gradually 
  sinking 
  to 
  116°. 
  

  

  Corroborative 
  evidence, 
  as 
  to 
  the 
  source 
  whence 
  the 
  water 
  derives 
  its 
  

   heat, 
  may 
  be 
  found 
  in 
  the 
  observation 
  that 
  the 
  temperature 
  of 
  the 
  dif- 
  

   ferent 
  springs 
  increases 
  with 
  their 
  proximity 
  to 
  the 
  recent 
  lava. 
  Thus 
  a 
  

   thermometer 
  immersed 
  in 
  the 
  most 
  northern 
  of 
  the 
  little 
  pools, 
  where 
  the 
  

   water 
  was 
  welling 
  out, 
  rose 
  to 
  106° 
  ; 
  in 
  the 
  next, 
  and 
  succeeding 
  ones, 
  to 
  

   107|°, 
  109°, 
  109|°, 
  lia.i°, 
  H4i°, 
  and 
  in 
  the 
  spring 
  nearest 
  to 
  the 
  lava 
  to 
  

   116°. 
  The 
  water 
  does 
  not 
  redden 
  litmus 
  paper, 
  and 
  no 
  smell 
  of 
  sulphu- 
  

   retted 
  hydrogen 
  was 
  remarked 
  at 
  the 
  spring 
  itself, 
  but 
  when 
  bottles 
  of 
  

   the 
  water 
  were 
  opened 
  some 
  weeks 
  afterwards 
  the 
  odour 
  was 
  very 
  per- 
  

   ceptible, 
  and 
  lead 
  test 
  paper 
  introduced 
  into 
  the 
  neck 
  was 
  soon 
  blackened. 
  

   The 
  total 
  solid 
  matter 
  was 
  found 
  to 
  be 
  — 
  ■ 
  

  

  Grammes 
  per 
  litre. 
  Grains 
  per 
  gallon. 
  

  

  „ 
  " 
  .. 
  , 
  , 
  C 
  water 
  taken 
  at 
  low 
  tide 
  . 
  3*32 
  232*3 
  

  

  Hot 
  spring 
  on 
  beach 
  ^ 
  ^ 
  ^ 
  ^ 
  n 
  ^ 
  h[gh 
  ^ 
  3 
  . 
  Q4 
  ^^ 
  

  

  Well 
  about 
  20 
  yards 
  inland 
  ; 
  water 
  taken 
  at 
  nearly 
  high 
  

  

  tide 
  3-14 
  219-6 
  

  

  The 
  main 
  saline 
  constituents 
  are 
  sodium 
  and 
  magnesium 
  as 
  chloride 
  

   and 
  sulphate, 
  with 
  calcium 
  and 
  magnesium 
  carbonate, 
  the 
  carbonates 
  

   amounting 
  to 
  about 
  one-fifth 
  of 
  the 
  total. 
  A 
  portion 
  of 
  the 
  salts 
  

   is 
  doubtless 
  derived 
  from 
  the 
  action 
  of 
  the 
  hot 
  water 
  on 
  the 
  rocks 
  

   it 
  passes 
  through, 
  the 
  remainder 
  being 
  due 
  to 
  mixture 
  with 
  sea- 
  

   water. 
  The 
  reason" 
  why 
  the 
  spring 
  is 
  slightly 
  less 
  saline 
  at 
  high 
  

  

  J 
  p 
  21. 
  

   ( 
  276 
  ) 
  

  

  