﻿[15] 
  

  

  REPORT 
  ON 
  THERMOMETERS. 
  

  

  199 
  

  

  instrument 
  is 
  graduated 
  upon 
  its 
  stem 
  towards 
  the 
  bulb 
  in 
  intervals 
  of 
  

   1° 
  F., 
  and 
  a 
  white 
  enamel 
  backing 
  facilitates 
  readings. 
  The 
  "whole 
  

   tube, 
  including 
  the 
  bulb, 
  is 
  surrounded 
  by 
  a 
  glass 
  

   protecting 
  cylinder, 
  sealed 
  at 
  both 
  ends, 
  to 
  take 
  up 
  

   the 
  pressure 
  of 
  the 
  sea 
  water, 
  and 
  is 
  9i 
  inches 
  in 
  

   length. 
  That 
  portion 
  of 
  the 
  protecting 
  cylinder 
  which 
  

   covers 
  the 
  bulb 
  is 
  nearly 
  rilled 
  with 
  mercury, 
  confined 
  

   by 
  a 
  partition 
  cemented 
  about 
  the 
  neck 
  of 
  the 
  bulb, 
  

   to 
  promote 
  conduction 
  of 
  heat 
  between 
  the 
  bulb 
  and 
  

   the 
  surrounding 
  water. 
  Made 
  by 
  Messrs. 
  ISTegretti 
  

   and 
  Zambra, 
  of 
  London. 
  

  

  When 
  in 
  use, 
  the 
  thermometer 
  is 
  attached 
  to 
  a 
  sound- 
  

   ing 
  liue, 
  and 
  lowered 
  into 
  the 
  water 
  bulb 
  downward. 
  

   At 
  the 
  desired 
  depth, 
  after 
  a 
  sufficient 
  delay 
  to 
  insure 
  

   its 
  having 
  taken 
  on 
  the 
  temperature 
  of 
  the 
  surrounding 
  

   water, 
  it 
  is 
  overset; 
  the 
  portion 
  of 
  mercury 
  contained 
  

   in 
  the 
  tube 
  above 
  the 
  constriction 
  

   breaks 
  off 
  at 
  that 
  point 
  and 
  stands 
  

   opposite 
  the 
  scale-reading 
  corre- 
  

   sponding 
  to 
  the 
  temperature. 
  It 
  

   may 
  be 
  read 
  at 
  any 
  time, 
  provided 
  

   that 
  it 
  be 
  kept 
  in 
  a 
  reversed 
  posi- 
  

   tion, 
  the 
  enlargement 
  at 
  the 
  end 
  of 
  

   the 
  tube 
  farthest 
  from 
  the 
  bulb 
  

   being 
  too 
  small 
  to 
  be 
  seriously 
  af- 
  

   fected 
  by 
  ordinary 
  temperature 
  

   changes. 
  

  

  The 
  first 
  form 
  of 
  this 
  valuable 
  

   invention, 
  as 
  presented 
  to 
  the 
  

   Eoyal 
  Society 
  of 
  London, 
  by 
  Henry 
  

   ^egretti 
  and 
  Joseph 
  Warren 
  Zam- 
  

   bra, 
  March 
  12, 
  1874,* 
  was 
  a 
  siphon 
  

   tube, 
  with 
  parallel 
  legs 
  and 
  a 
  con- 
  

   siderable 
  enlargement 
  at 
  the 
  bend. 
  

   (Fig. 
  9.) 
  Instead 
  of 
  the 
  double 
  

   curve, 
  small 
  reservoir, 
  and 
  con- 
  

   striction 
  in 
  the 
  tube 
  of 
  the 
  later 
  

   forms, 
  there 
  was 
  a 
  single 
  funnel- 
  

   shaped 
  curve 
  above 
  the 
  bulb, 
  con- 
  

   taining 
  a 
  small 
  glass 
  plug, 
  similar 
  

   to 
  that 
  used 
  in 
  Negretti 
  and 
  Zarn- 
  

   bra's 
  patent 
  maximum 
  thermom- 
  

   eter. 
  The 
  office 
  of 
  this 
  plug 
  was 
  to 
  

   close 
  the 
  tube 
  on 
  reversal 
  and 
  cause 
  

   the 
  column 
  of 
  mercury 
  to 
  break 
  off 
  

   at 
  that 
  point. 
  The 
  instrument 
  was 
  

  

  &Li 
  

  

  Tig. 
  8.— 
  The 
  Xegretti- 
  

   Zanibra 
  self-register- 
  

   ing 
  deep-sea 
  thermom- 
  

   eter, 
  modern 
  form. 
  

  

  Fig. 
  9. 
  — 
  Xegretti 
  and 
  

   Zambra's 
  self-register- 
  

   ing 
  deep-sea 
  thermom- 
  

   eter, 
  earliest 
  form. 
  

  

  * 
  Proc. 
  Royal 
  Society, 
  1874. 
  Vol. 
  22. 
  

  

  