﻿204 
  

  

  REPORT 
  OF 
  COMMISSIONER 
  OF 
  FISH 
  AND 
  FISHERIES. 
  

  

  [20] 
  

  

  error 
  exceeding 
  one-half 
  a 
  degree. 
  By 
  increasing 
  the 
  length 
  of 
  the 
  

   stem 
  and 
  restricting 
  the 
  graduation 
  to 
  the 
  range 
  between 
  32° 
  and 
  90°, 
  

   it 
  would 
  be 
  possible 
  to 
  point 
  the 
  stem 
  to 
  fifths 
  of 
  a 
  degree, 
  for 
  special 
  

   observations 
  at 
  great 
  depths, 
  where 
  the 
  variations 
  of 
  temperature 
  are 
  

   small. 
  

  

  With 
  the 
  exception 
  of 
  the 
  single 
  specimen 
  tried 
  and 
  reported 
  ad- 
  

   versely 
  upon 
  by 
  the 
  Coast 
  Survey 
  in 
  1875 
  (see 
  p. 
  [16]), 
  the 
  earlier 
  forms 
  of 
  

   reversing 
  gear 
  for 
  these 
  thermometers 
  have 
  never, 
  to 
  my 
  knowledge, 
  

   been 
  used 
  in 
  this 
  country. 
  As 
  first 
  used 
  by 
  the 
  Fish 
  Commission 
  in 
  

   1877, 
  the 
  thermometers 
  were 
  inclosed 
  in 
  wooden 
  cases, 
  about 
  13 
  inches 
  

   long, 
  secured 
  to 
  the 
  sounding 
  line 
  by 
  a 
  lanyard 
  about 
  6 
  feet 
  long 
  at- 
  

   tached 
  to 
  the 
  bulb 
  end. 
  The 
  case 
  was 
  hollowed 
  out 
  inside, 
  and 
  con- 
  

   tained 
  a 
  quantity 
  of 
  small 
  shot, 
  movable 
  from 
  end 
  to 
  end, 
  sufficient 
  to 
  

   nearly, 
  but 
  not 
  quite, 
  overcome 
  its 
  buoyancy 
  in 
  sea 
  water. 
  On 
  send- 
  

   ing 
  the 
  case 
  down 
  the 
  shot 
  fell 
  to 
  its 
  bulb 
  end 
  and 
  tended 
  to 
  keep 
  it 
  

   upright 
  in 
  the 
  water. 
  On 
  reversing 
  the 
  motion 
  and 
  hauling 
  in 
  the 
  line, 
  

   the 
  case 
  was 
  overset, 
  the 
  shot 
  ran 
  to 
  its 
  other 
  end, 
  and 
  tended 
  to 
  keep 
  

   its 
  bulb 
  uppermost. 
  (Fig. 
  12.) 
  

  

  

  FiG. 
  12. 
  — 
  Negretti-Zambra 
  thermometers 
  in 
  wooden 
  cases, 
  as 
  first 
  used 
  by 
  the 
  Fish 
  Commission. 
  

  

  For 
  the 
  moderate 
  depths 
  at 
  first 
  explored 
  this 
  contrivance 
  answered 
  

   very 
  well, 
  due 
  care 
  being 
  taken 
  that 
  the 
  acts 
  of 
  lowering 
  and 
  hauling 
  

   in 
  were 
  continuous. 
  At 
  800 
  fathoms, 
  however, 
  Commander 
  J. 
  E. 
  Bart- 
  

  

  