﻿1874.] 
  On 
  the 
  Distribution 
  of 
  Temperature 
  in 
  the 
  Ocean. 
  123 
  

  

  through 
  considerable 
  changes 
  of 
  temperature, 
  and 
  renewing 
  the 
  surface 
  

   for 
  repeated 
  polishings, 
  are 
  also 
  described. 
  The 
  mode 
  of 
  construction 
  of 
  a 
  

   bed 
  of 
  hones 
  for 
  bringing 
  the 
  curve 
  of 
  the 
  speculum 
  back 
  to 
  the 
  sphere, 
  

   if 
  it 
  should 
  happen 
  to 
  have 
  gone 
  beyond 
  the 
  parabola 
  in 
  the 
  polishing, 
  

   without 
  reverting 
  to 
  the 
  emery-grinder, 
  is 
  also 
  explained 
  ; 
  and 
  a 
  word 
  

   or 
  two 
  is 
  added 
  respecting 
  the 
  treatment 
  of 
  the 
  speculum 
  when 
  finished. 
  

  

  II. 
  " 
  Note 
  on 
  the 
  Vertical 
  Distribution 
  of 
  Temperature 
  in 
  the 
  

   Ocean/' 
  By 
  J. 
  Y. 
  Buchanan, 
  Chemist 
  on 
  board 
  H.M.S. 
  

   ' 
  Challenger/ 
  Communicated 
  by 
  Prof. 
  A. 
  W. 
  Williamson, 
  

   For. 
  Sec. 
  U.S. 
  Received 
  November 
  11, 
  1874. 
  

   From 
  newspapers 
  and 
  other 
  reports 
  which 
  have 
  been 
  received 
  by 
  late 
  

   mails, 
  it 
  appears 
  that 
  the 
  distribution 
  of 
  temperature 
  in 
  the 
  ocean 
  is 
  

   occupying 
  the 
  attention 
  of 
  a 
  certain 
  portion 
  of 
  the 
  scientific 
  public, 
  and 
  

   even 
  giving 
  rise 
  to 
  considerable 
  discussion. 
  The 
  observations 
  made 
  on 
  

   board 
  this 
  ship, 
  and 
  more 
  especially 
  in 
  the 
  Atlantic, 
  have 
  furnished 
  the 
  

   greater 
  part 
  of 
  the 
  material 
  on 
  which 
  the 
  various 
  speculations 
  have 
  

   been 
  founded. 
  It 
  appears 
  to 
  me 
  that 
  one 
  point 
  suggested 
  by 
  these 
  

   observations 
  has 
  not 
  received 
  sufficient 
  attention 
  from 
  those 
  w 
  T 
  ho 
  have 
  

   written 
  and 
  spoken 
  on 
  the 
  subject 
  : 
  I 
  mean, 
  the 
  effect 
  of 
  the 
  changing 
  

   seasons 
  on 
  sea-water. 
  Consider 
  the 
  state 
  of 
  the 
  water 
  at 
  and 
  near 
  the 
  

   surface 
  of 
  the 
  ocean, 
  somewhere 
  not 
  in 
  the 
  tropics. 
  To 
  be 
  more 
  pre- 
  

   cise, 
  let 
  us 
  suppose 
  that 
  we 
  have 
  taken 
  up 
  our 
  position 
  in 
  the 
  middle 
  of 
  

   the 
  North 
  Atlantic, 
  somewhere 
  about 
  the 
  30th 
  parallel. 
  This 
  part 
  of 
  

   the 
  ocean 
  is 
  not 
  vexed 
  with 
  currents, 
  and 
  affords 
  the 
  best 
  possible 
  field 
  

   for 
  the 
  observation 
  of 
  the 
  phenomenon 
  in 
  question. 
  The 
  whole 
  ocean 
  en- 
  

   closed 
  by 
  the 
  20th 
  and 
  40th 
  parallels 
  of 
  north 
  latitude 
  and 
  the 
  meridians 
  

   of 
  30° 
  and 
  60° 
  west 
  longitude 
  forms 
  one 
  oceanic 
  lake, 
  not 
  affected 
  by 
  

   the 
  perturbing 
  influence 
  of 
  currents 
  or 
  of 
  land, 
  and 
  where, 
  therefore, 
  the 
  

   true 
  effect 
  of 
  differences 
  of 
  atmospheric 
  temperature 
  on 
  the 
  waters 
  of 
  

   the 
  ocean 
  may 
  be 
  most 
  advantageously 
  studied. 
  Let 
  us 
  assume 
  the 
  

   winter 
  temperature 
  of 
  the 
  surface-water 
  to 
  be 
  60° 
  F. 
  and 
  the 
  summer 
  

   temperature 
  to 
  be 
  70° 
  F. 
  If 
  we 
  start 
  from 
  midwinter, 
  we 
  find 
  that, 
  as 
  

   summer 
  approaches, 
  the 
  surface-water 
  must 
  get 
  gradually 
  warmer, 
  and 
  

   that 
  the 
  temperature 
  of 
  the 
  layers 
  below 
  the 
  surface 
  must 
  decrease 
  at 
  a 
  

   very 
  rapid 
  rate, 
  until 
  the 
  stratum 
  of 
  winter 
  temperature, 
  or 
  60° 
  F., 
  is 
  

   reached 
  ; 
  in 
  the 
  language 
  of 
  the 
  isothermal 
  charts, 
  the 
  isothermal 
  line 
  for 
  

   degrees 
  between 
  70° 
  F. 
  (if 
  we 
  suppose 
  that 
  we 
  have 
  arrived 
  at 
  mid- 
  

   summer) 
  and 
  60° 
  F. 
  open 
  out 
  or 
  increase 
  their 
  distance 
  from 
  each 
  other 
  

   as 
  the 
  depth 
  increases. 
  Let 
  us 
  now 
  consider 
  the 
  conditions 
  after 
  the 
  

   summer 
  heat 
  has 
  begun 
  to 
  waver. 
  During 
  the 
  whole 
  period 
  of 
  heating, 
  

   the 
  water, 
  from 
  its 
  increasing 
  temperature, 
  has 
  been 
  always 
  becoming 
  

   lighter, 
  so 
  that 
  heat 
  communication 
  by 
  convection 
  with 
  the 
  water 
  below 
  

   has 
  been 
  entirely 
  suspended 
  during 
  the 
  whole 
  period. 
  The 
  heating 
  of 
  

  

  