﻿192 
  

  

  REPORT 
  OF 
  COMMISSIONER 
  OF 
  FISH 
  AND 
  FISHERIES. 
  

  

  [8] 
  

  

  mercury 
  are 
  wholly 
  filled 
  with 
  a 
  mixture 
  of 
  creosote 
  and 
  water.* 
  The 
  

   smaller 
  bulb 
  aud 
  limb 
  are 
  partly 
  filled 
  with 
  the 
  same 
  mixture 
  aud 
  partly 
  

  

  with 
  compressed 
  air. 
  On 
  each 
  side, 
  iu 
  

   the 
  tube 
  above 
  the 
  mercury, 
  is 
  a 
  small 
  steel 
  

   index, 
  having 
  a 
  human 
  hair 
  tied 
  around 
  its 
  

   upper 
  end 
  to 
  keep 
  it 
  in 
  place. 
  The 
  fluid 
  

   acted 
  upon 
  by 
  temperature 
  is 
  that 
  in 
  the 
  

   larger 
  bulb. 
  As 
  the 
  temperature 
  rises 
  

   the 
  mercurial 
  column 
  is 
  forced 
  over 
  into 
  

   the 
  other 
  limb, 
  driving 
  the 
  index 
  before 
  

   it. 
  As 
  the 
  temperature 
  falls 
  the 
  com- 
  

   pressed 
  air 
  in 
  the 
  smaller 
  bulb 
  acts 
  as 
  a 
  

   spring 
  to 
  send 
  the 
  mercury 
  back 
  again, 
  

   driving 
  the 
  other 
  index 
  before 
  it, 
  and 
  

   leaving 
  the 
  first 
  index 
  at 
  the 
  highest 
  point 
  

   it 
  had 
  reached. 
  It 
  is 
  thus 
  a 
  self-register- 
  

   ing 
  maximum 
  and 
  minimum 
  thermometer, 
  

   and 
  the 
  scales 
  are 
  therefore 
  graduated 
  in 
  

   opposite 
  directions. 
  The 
  steel 
  indices 
  are 
  

   set 
  by 
  means 
  of 
  a 
  small 
  magnet, 
  grooved 
  

   across 
  its 
  poles 
  to 
  permit 
  close 
  coaptation 
  

   to 
  the 
  tubes. 
  The 
  larger 
  bulb 
  is 
  made 
  

   double, 
  according 
  to 
  the 
  recommendation 
  

   of 
  Dr. 
  W. 
  A. 
  Miller, 
  vice-president 
  of 
  the 
  

   Royal 
  Society 
  (in 
  April, 
  1SG9), 
  being 
  sur- 
  

   rounded 
  by 
  another 
  bulb, 
  and 
  the 
  inter- 
  

   vening 
  space 
  nearly, 
  but 
  not 
  quite, 
  filled 
  by 
  alcohol. 
  Made 
  by 
  Mr. 
  L. 
  

   Casella, 
  of 
  London. 
  

  

  In 
  the 
  original 
  form 
  of 
  this 
  instrument, 
  invented 
  by 
  Negretti 
  and 
  

   Zambra 
  (see 
  page 
  [13]), 
  this 
  space 
  between 
  the 
  larger 
  bulb 
  and 
  its 
  pro- 
  

   tecting 
  shield 
  was 
  partly 
  filled 
  with 
  mercury, 
  a 
  better 
  conductor 
  of 
  heat 
  

   than 
  alcohol. 
  The 
  instruments 
  are 
  advertised 
  as 
  having 
  been 
  sub- 
  

   jected 
  to 
  hydraulic 
  pressures 
  equal 
  to 
  five 
  tons 
  to 
  the 
  square 
  inch, 
  be- 
  

   fore 
  leaving 
  the 
  makers' 
  hands. 
  

  

  The 
  Miller-Casella 
  thermometers 
  now 
  in 
  stock 
  and 
  recently 
  in 
  use 
  

   by 
  the 
  Fish 
  Commission 
  agree 
  with 
  the 
  foregoing 
  description 
  and 
  with 
  

   Fig. 
  5, 
  excepting 
  in 
  that 
  the 
  "aneurisms, 
  "t 
  as 
  Professor 
  Tait 
  has 
  called 
  

   them, 
  or 
  little 
  swellings 
  of 
  the 
  tube 
  near 
  the 
  bends 
  of 
  the 
  U 
  have 
  been 
  

   omitted, 
  perhaps 
  because 
  of 
  Professor 
  Tait's 
  criticisms. 
  The 
  form 
  figured 
  

   is 
  that 
  which 
  was 
  first 
  used 
  in 
  the 
  cruises 
  of 
  the 
  Porcupine 
  in 
  18G9 
  and 
  

   1870, 
  of 
  the 
  Pomerania 
  in 
  1872, 
  by 
  the 
  Norwegian 
  expedition 
  in 
  1876-'78, 
  

  

  " 
  Iu 
  the 
  Challenger 
  Narrative, 
  vol. 
  i, 
  p. 
  86, 
  it 
  is 
  stated 
  that 
  the 
  hulb 
  contains 
  creo- 
  

   sote 
  and 
  alcohol. 
  

  

  t 
  From 
  dvEvpv6/.ta, 
  a 
  swelling 
  (dvd 
  and 
  Evpvi), 
  not 
  a 
  — 
  vsupoi, 
  as 
  more 
  com- 
  

   monly 
  derived. 
  (Scientific 
  Results 
  Voyage 
  of 
  Challenger, 
  Narrative, 
  vol. 
  2, 
  Appendix 
  A, 
  

  

  Fig. 
  5.— 
  The 
  Miller-Casella 
  deep-sea 
  ther- 
  

   mometer, 
  iu 
  ami 
  out 
  of 
  case. 
  

  

  