﻿XIII.— 
  REPORT 
  ON 
  THE 
  THERMOMETERS 
  OF 
  THE 
  U. 
  S. 
  COMMIS- 
  

   SION 
  OF 
  FISH 
  AND 
  FISHERIES. 
  

  

  By 
  J. 
  H. 
  Kidder, 
  M. 
  D. 
  

  

  CORRECTION. 
  

  

  In 
  the 
  earlier 
  operations 
  of 
  the 
  Commission 
  its 
  thermometers 
  were 
  

   used 
  as 
  they 
  came 
  from 
  the 
  makers, 
  without 
  previous 
  comparison 
  with 
  

   standards. 
  As 
  the 
  number 
  of 
  temperature 
  observations 
  increased, 
  and 
  

   their 
  importance 
  became 
  more 
  evident, 
  instrumental 
  errors 
  were 
  re- 
  

   ported 
  from 
  time 
  to 
  time, 
  which 
  tended 
  to 
  discredit 
  some 
  of 
  the 
  obser- 
  

   vations, 
  and 
  to 
  weaken 
  the 
  force 
  of 
  the 
  inferences 
  deduced 
  from 
  them. 
  

   In 
  the 
  comparison 
  of 
  temperatures 
  observed 
  at 
  considerable 
  depths 
  in 
  

   the 
  sea, 
  where 
  the 
  differences 
  recorded 
  are 
  small, 
  instrumental 
  errors 
  

   become 
  particularly 
  important, 
  audit 
  was 
  decided 
  by 
  the 
  Commissioner 
  

   that 
  all 
  the 
  thermometers 
  used 
  by 
  the 
  Commission 
  should 
  be 
  compared 
  

   and 
  their 
  errors 
  noted 
  before 
  their 
  issue. 
  

  

  This 
  duty 
  was 
  assigned 
  to 
  me 
  early 
  in 
  the 
  autumn 
  of 
  1S83, 
  and 
  the 
  

   report 
  which 
  follows 
  covers 
  the 
  period 
  from 
  December 
  12, 
  1883, 
  when 
  

   the 
  first 
  corrections 
  were 
  made, 
  to 
  May 
  1, 
  1885. 
  

  

  At 
  the 
  outset 
  comparisons 
  were 
  made 
  with 
  two 
  standard 
  thermom- 
  

   eters, 
  manufactured 
  by 
  L. 
  Casella, 
  of 
  London, 
  one 
  graduated 
  according 
  

   to 
  the 
  Fahrenheit 
  and 
  the 
  other 
  to 
  the 
  centigrade 
  scale. 
  These 
  instru- 
  

   ments 
  had 
  been 
  procured 
  through 
  the 
  London 
  agent 
  of 
  the 
  Smithsonian 
  

   Institution, 
  and 
  had 
  been 
  verified 
  at 
  the 
  Kew 
  Observatory. 
  The 
  tubes 
  

   were 
  certified 
  to 
  by 
  the 
  maker 
  as 
  having 
  been 
  thoroughly 
  " 
  seasoned" 
  

   before 
  pointing, 
  and 
  the 
  centigrade 
  which 
  survives 
  (the 
  Fahrenheit 
  was 
  

   broken 
  December 
  20, 
  1883), 
  shows 
  no 
  change 
  in 
  the 
  zero 
  point 
  up 
  to 
  

   this 
  writing. 
  

  

  Subsequently 
  (February 
  28, 
  1881), 
  two 
  fine 
  standards, 
  both 
  graduated 
  

   according 
  to 
  the 
  Fahrenheit 
  scale, 
  were 
  received 
  from 
  J. 
  Hicks, 
  of 
  Lou- 
  

   don, 
  which 
  had 
  also 
  been 
  verified 
  at 
  the 
  Kew 
  Observatory. 
  One 
  of 
  these 
  

   instruments 
  has 
  been 
  used 
  in 
  all 
  comparisons 
  since 
  the 
  day 
  of 
  receipt. 
  

   They 
  are 
  pointed 
  to 
  fifths 
  of 
  a 
  degree, 
  allowing 
  a 
  good 
  reading 
  to 
  tenths 
  

   of 
  a 
  degree, 
  and 
  cover 
  the 
  range 
  from 
  10° 
  to 
  120° 
  F. 
  

  

  The 
  corrections 
  were 
  got 
  at 
  first 
  by 
  immersing 
  the 
  instruments 
  to 
  be 
  

   compared, 
  together 
  with 
  the 
  standard, 
  in 
  water 
  contained 
  in 
  a 
  large 
  

   cylindrical 
  glass 
  vessel, 
  provided 
  with 
  a, 
  ring 
  stirrer 
  and 
  covered 
  by 
  a 
  

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