﻿190 
  REPORT 
  OF 
  COMMISSIONER 
  OF 
  FISH 
  AND 
  FISHERIES. 
  [6] 
  

  

  THE 
  INSTRUMENT. 
  

  

  The 
  following 
  are 
  the 
  kinds 
  of 
  thermometers 
  principally 
  used 
  by 
  the 
  

   Commission: 
  

  

  (1) 
  Beclc 
  thermometers 
  (Fig. 
  3). 
  — 
  These 
  are 
  in 
  form 
  like 
  the 
  "brew- 
  

   er's 
  thermometers" 
  of 
  the 
  trade; 
  plain 
  tubes 
  with 
  round 
  bulbs, 
  gradu- 
  

   ated 
  upon 
  a 
  white 
  metal 
  scale 
  to 
  divisions 
  of 
  2° 
  F., 
  and 
  

   ranging 
  from 
  — 
  30° 
  to 
  + 
  120° 
  F. 
  They 
  are 
  inclosed 
  in 
  

   plain 
  copper 
  cases, 
  open 
  in 
  front, 
  with 
  a 
  cup 
  at 
  the 
  bot- 
  

   tom, 
  perforated 
  by 
  a 
  central 
  hole. 
  This 
  cup 
  can 
  be 
  closed 
  

   by 
  a 
  cork 
  and 
  will 
  then 
  hold 
  water. 
  Made 
  by 
  Charles 
  

   Wilder, 
  of 
  Peterborough, 
  IN". 
  II., 
  in 
  two 
  sizes, 
  10 
  inches 
  

   and 
  14 
  inches 
  long, 
  used 
  mostly 
  for 
  air 
  temperatures 
  and" 
  

   for 
  temperatures 
  of 
  surface 
  water. 
  

  

  These 
  instruments, 
  although 
  cheap 
  and 
  not 
  pointed 
  to 
  

   less 
  than 
  2°, 
  are 
  now 
  very 
  trustworthy, 
  the 
  maker 
  fur- 
  

   nishing 
  the 
  Commission 
  with 
  " 
  seasoned" 
  tubes. 
  The 
  first 
  

   seven 
  received 
  showed 
  a 
  maximum 
  error 
  of 
  1.1°, 
  mini- 
  

   mum 
  0°, 
  and 
  mean 
  of 
  0.32°, 
  between 
  32° 
  and 
  92°. 
  The 
  

   last 
  nine 
  arc, 
  much 
  better, 
  showing 
  a 
  maximum 
  error 
  of 
  

   0,5°, 
  minimum 
  of 
  0°, 
  and 
  mean 
  of 
  0.1°. 
  The 
  spaces 
  in 
  

   graduation 
  arc 
  wide, 
  and 
  might 
  profitably 
  be 
  divided 
  so 
  

   as 
  to 
  indicate 
  single 
  degrees. 
  

  

  Six 
  deck 
  thermometers, 
  of 
  similar 
  form 
  to 
  those 
  above 
  

   described, 
  made 
  by 
  J. 
  & 
  II. 
  J. 
  Green, 
  of 
  New 
  York, 
  are- 
  

   graduated 
  upon 
  the 
  stems 
  to 
  intervals 
  of 
  1°, 
  and 
  rate 
  with 
  

   remarkable 
  uniformity, 
  with 
  a 
  maximum 
  error 
  of 
  0.3°, 
  

   minimum 
  of 
  0°, 
  and 
  mean 
  of 
  0.1°. 
  

  

  (2) 
  "Protected" 
  thermometers, 
  with 
  round 
  bulbs, 
  grad- 
  

   uated 
  upon 
  a 
  white-metal 
  scale 
  to 
  1° 
  intervals, 
  and 
  rang- 
  

   ing 
  from 
  — 
  30° 
  to 
  120° 
  F. 
  These 
  thermometers 
  are 
  in- 
  

   closed 
  in 
  cylindrical 
  copper 
  cases 
  (devised 
  by 
  Professor 
  

   Baird 
  in 
  IS73), 
  with 
  a 
  hinged 
  door 
  in 
  front. 
  There 
  is 
  no 
  

   perforation 
  in 
  the 
  bottom 
  of 
  the 
  cup, 
  which 
  is 
  3 
  inches 
  

   long 
  by 
  If 
  inches 
  wide 
  (Fig. 
  4) 
  ; 
  total 
  length 
  12 
  inches; 
  

   a 
  stout 
  ring 
  at 
  each 
  end 
  ; 
  made 
  by 
  Charles 
  Wilder, 
  of 
  

   Peterborough, 
  N. 
  II.; 
  used 
  mostly 
  for 
  reading 
  water 
  temperatures 
  at 
  

   light-houses, 
  and 
  at 
  shore 
  stations 
  of 
  the 
  Commission. 
  For 
  depths 
  down 
  

   to 
  live 
  fathoms 
  these 
  thermometers 
  will 
  indicate 
  closely 
  the 
  temperature 
  

   of 
  the 
  water 
  below 
  the 
  surface, 
  some 
  of 
  the 
  water 
  being 
  caught 
  and 
  held 
  

   by 
  the 
  cup 
  at 
  the 
  bottom. 
  The 
  cylindrical 
  copper 
  cases 
  protect 
  the 
  

   tubes 
  from 
  damage 
  by 
  striking 
  against 
  rocks, 
  &c. 
  

  

  These 
  thermometers 
  also 
  show 
  a 
  considerable 
  improvement 
  in 
  accuracy 
  

   since 
  the 
  maker 
  has 
  been 
  furnishing 
  seasoned 
  tubes. 
  The 
  first 
  four 
  com- 
  

   pared 
  gave 
  a 
  maximum 
  error 
  of 
  1.3°, 
  minimum 
  of 
  0°, 
  and 
  mean 
  of 
  0.58°. 
  

   The 
  next 
  fifteen 
  showed 
  a 
  maximum 
  error 
  of 
  l°,^iuimum 
  0°, 
  mean 
  0.34°. 
  

  

  J 
  

  

  FIG. 
  3.— 
  Deck 
  ther- 
  

   mometer. 
  

  

  