﻿[9] 
  REPORT 
  ON 
  THERMOMETERS. 
  193 
  

  

  in 
  the 
  cruises 
  of 
  the 
  Valorous 
  in 
  1875, 
  of 
  the 
  Challenger 
  in 
  1873-'76, 
  of 
  

   the 
  Nares 
  Arctic 
  Expedition 
  in 
  1876, 
  and 
  by 
  the 
  U. 
  S. 
  Coast 
  Survey 
  

   and 
  Fish 
  Commission 
  up 
  to 
  a 
  recent 
  date. 
  

  

  Although 
  justly 
  regarded 
  as 
  a 
  most 
  important 
  improvement 
  upon 
  the 
  

   unprotected 
  Sixe's 
  thermometers 
  used 
  prior 
  to 
  the 
  year 
  1869 
  (with 
  ex- 
  

   ceptions 
  to 
  be 
  hereafter 
  noted), 
  these 
  instruments 
  are 
  not 
  free 
  from 
  de- 
  

   fects 
  and 
  individual 
  peculiarities, 
  which 
  have 
  doubtless 
  often 
  led 
  to 
  

   erroneous 
  readings. 
  

  

  In 
  the 
  first 
  place, 
  the 
  indices 
  are 
  likely 
  to 
  slip, 
  especially 
  since 
  the 
  

   use 
  of 
  steam 
  winches 
  and 
  of 
  wire 
  for 
  sounding, 
  imparting 
  a 
  peculiar 
  

   jarring 
  motion 
  to 
  the 
  whole 
  line. 
  "Even 
  a 
  slight 
  jerk 
  causes 
  the 
  index 
  

   to 
  move 
  up 
  or 
  down," 
  says 
  Sir 
  Wyville 
  Thomson, 
  * 
  who 
  found 
  one 
  or 
  

   two 
  thermometers 
  to 
  be 
  wrong 
  from 
  this 
  cause 
  "in 
  almost 
  every 
  serial 
  

   temperature 
  sounding." 
  

  

  Then, 
  again, 
  since 
  these 
  thermometers 
  register 
  only 
  the 
  maximum 
  

   and 
  mininimum 
  temperatures 
  which 
  they 
  encounter, 
  in 
  the 
  possible 
  case 
  

   of 
  a 
  warmer 
  stratum 
  of 
  water 
  underlying 
  a 
  colder 
  one 
  of 
  less 
  specific 
  

   gravity, 
  or 
  in 
  the 
  case 
  that 
  the 
  air 
  is 
  colder 
  than 
  the 
  water, 
  the 
  final 
  

   registration 
  may 
  not 
  be 
  a 
  correct 
  indication 
  of 
  the 
  temperatures 
  met 
  

   with, 
  the 
  instruments 
  registering 
  on 
  their 
  minimum 
  sides 
  either 
  the 
  

   temperature 
  of 
  the 
  colder 
  overlying 
  stratum 
  of 
  water, 
  or 
  of 
  the 
  air, 
  

   which 
  may 
  be 
  inadvertently 
  or 
  ignorantly 
  read 
  as 
  that 
  of 
  the 
  greatest 
  

   depth 
  measured. 
  When 
  the 
  air 
  is 
  colder 
  than 
  the 
  water 
  the 
  thermome- 
  

   ters 
  may 
  be 
  artificially 
  warmed 
  before 
  sending 
  them 
  down, 
  but 
  a 
  

   colder 
  overlying 
  stratum 
  of 
  water 
  offers 
  much 
  greater 
  difficulties, 
  which 
  

   were 
  fully 
  recognized 
  by 
  the 
  Challenger 
  observers. 
  Sir 
  Wyville 
  Thom- 
  

   son 
  says, 
  to 
  this 
  point 
  :t 
  "Very 
  frequently, 
  especially 
  at 
  considerable 
  

   depths, 
  where 
  the 
  differences 
  were 
  very 
  slight, 
  thermometers 
  sent 
  to 
  

   greater 
  depths 
  gave 
  indications 
  higher 
  than 
  those 
  above 
  them. 
  * 
  * 
  * 
  

   I 
  have 
  no 
  hesitation 
  therefore 
  in 
  saying 
  that 
  a 
  single 
  indication 
  with 
  a 
  

   thermometer 
  on 
  Sixe's 
  principle 
  is 
  not 
  trustworthy, 
  and 
  that 
  a 
  fact 
  in 
  

   temperature 
  distribution 
  can 
  only 
  be 
  established 
  by 
  a 
  series 
  of 
  corrobo- 
  

   rative 
  determinations." 
  

  

  Another 
  peculiarity, 
  which 
  fortunately 
  tends 
  to 
  compensate 
  that 
  last 
  

   described, 
  is 
  that 
  these 
  instruments 
  are 
  extremely 
  sloiv. 
  According 
  to 
  

   my 
  laboratory 
  observations 
  quite 
  twenty 
  minutes 
  are 
  required 
  for 
  the 
  

   change 
  from 
  the 
  temperature 
  of 
  the 
  air 
  (60°-70°) 
  to 
  the 
  freezing-point, 
  

   the 
  thermometers 
  being 
  immersed 
  in 
  melting 
  ice.f 
  It 
  is 
  possible 
  that, 
  

   inasmuch 
  as 
  a 
  self-registering 
  thermometer 
  in 
  actual 
  use 
  is 
  recording 
  

  

  *Voyage 
  of 
  the 
  Challenger. 
  The 
  Atlantic, 
  vol. 
  2. 
  p. 
  259. 
  See 
  also 
  Sigsbee's 
  Deep- 
  

   Sea 
  Sounding 
  and 
  Dredging, 
  p. 
  110. 
  

  

  \Op. 
  cit., 
  vol. 
  2. 
  p. 
  260; 
  also 
  Sigsbee, 
  p. 
  112. 
  "From 
  what 
  has 
  been 
  said 
  it 
  is 
  seen 
  

   that 
  a 
  maximum 
  and 
  minimum 
  thermometer 
  is 
  not 
  well 
  adapted 
  to 
  ascertaining 
  the 
  

   temperature 
  of 
  intermediate 
  warm 
  or 
  cold 
  strata." 
  

  

  t 
  See 
  also 
  Commander 
  Beardslee's 
  observations, 
  Rep. 
  Com. 
  Fish 
  and 
  Fisheries, 
  1877, 
  

   App. 
  C, 
  and 
  Coast 
  Survey 
  comparisons, 
  quoted 
  by 
  Sigsbee, 
  op. 
  cit., 
  pp. 
  114-119. 
  

   S. 
  Mis. 
  70 
  13 
  

  

  