﻿212 
  

  

  REPORT 
  OF 
  COMMISSIONER 
  OF 
  FISH- 
  AND 
  FISHERIES. 
  

  

  [28] 
  

  

  frame 
  altogether. 
  There 
  is 
  a 
  longitudinal 
  slit 
  in 
  the 
  case, 
  uncover- 
  

   ing 
  the 
  thermometer 
  scale, 
  and 
  a 
  corresponding 
  slit 
  on 
  the 
  opposite 
  

   side, 
  so 
  that 
  the 
  temperature 
  can 
  be 
  read 
  by 
  holding 
  the 
  instrument 
  

   up 
  against 
  the 
  light. 
  To 
  guard 
  against 
  the 
  "jiggling" 
  motion 
  com- 
  

   municated 
  from 
  the 
  reeling 
  engine 
  along 
  the 
  wire 
  rope 
  or 
  sounding 
  

   wire 
  now 
  universally 
  used 
  by 
  the 
  Fish 
  Commission, 
  which 
  was 
  found 
  

   during 
  the 
  Albatross 
  cruise 
  of 
  1S83-'S4 
  to 
  have 
  in 
  some 
  cases 
  jarred 
  

   the 
  mercury 
  from 
  the 
  bulb 
  into 
  the 
  tube 
  after 
  reversal, 
  spiral 
  springs 
  

   Lave 
  been 
  introduced 
  into 
  the 
  metal 
  case 
  above 
  and 
  below 
  the 
  ther- 
  

   mometer. 
  The 
  whole 
  instrument 
  is 
  heavily 
  nickel-plated 
  to 
  prevent 
  

   rust, 
  and 
  works 
  well 
  in 
  practice. 
  

  

  To 
  guard 
  against 
  parallax 
  errors 
  in 
  reading 
  (see 
  p. 
  [5]) 
  I 
  have 
  had 
  

   constructed 
  by 
  Mr. 
  Joseph 
  Zentmayer, 
  of 
  Philadelphia, 
  a 
  reading 
  lens 
  

  

  of 
  about 
  3 
  inches 
  focal 
  length, 
  fitted 
  at 
  

   light 
  angles 
  to 
  the 
  center 
  of 
  a 
  brass 
  sad- 
  

   dle 
  adapted 
  to 
  the 
  convex 
  surface 
  of 
  the 
  

   thermometer 
  case, 
  and 
  provided 
  with 
  a 
  

   short 
  draw-tube 
  for 
  focussing. 
  The 
  eye- 
  

   piece 
  opening 
  is 
  made 
  smaller 
  than 
  the 
  

   pupil 
  of 
  the 
  eye, 
  and 
  there 
  is 
  therefore 
  no 
  

   variation 
  in 
  the 
  reading, 
  whatever 
  be 
  the 
  

   inclination 
  to 
  the 
  perpendicular 
  at 
  which 
  

   the 
  scale 
  is 
  viewed. 
  (See 
  Fig. 
  20.) 
  The 
  

   slight 
  magnifying 
  power 
  of 
  the 
  lens 
  makes 
  

   it 
  much 
  easier 
  than 
  formerly 
  to 
  read 
  the 
  

   temperature 
  to 
  fractions 
  of 
  a 
  degree. 
  

  

  The 
  abandonment 
  of 
  the 
  propeller 
  re- 
  

   versing-gear 
  by 
  French 
  and 
  Scottish 
  ob- 
  

   servers 
  seems 
  to 
  have 
  been 
  due 
  partly 
  to 
  a 
  fear 
  that 
  the 
  propeller- 
  

   fans 
  might 
  be 
  turned 
  by 
  a 
  strong 
  lateral 
  current, 
  as 
  for 
  example 
  in 
  

   the 
  Straits 
  of 
  Gibraltar 
  (see 
  Challenger 
  Narrative, 
  vol. 
  1, 
  p. 
  93), 
  and 
  

   partly, 
  as 
  stated 
  in 
  M. 
  Filhol's 
  report 
  on 
  the 
  work 
  of 
  the 
  Talisman, 
  

   by 
  the 
  observation 
  that 
  the 
  fans 
  have 
  sometimes 
  failed 
  to 
  revolve 
  

   at 
  all. 
  In 
  the 
  Bailie-Tanner 
  case 
  the 
  protecting 
  shield 
  around 
  the 
  pro- 
  

   peller 
  would 
  meet 
  the 
  former 
  objection 
  (so 
  long 
  as 
  the 
  instrument 
  re- 
  

   mained 
  in 
  a 
  perpendicular 
  position) 
  if 
  currents 
  strong 
  enough 
  to 
  affect 
  

   the 
  fans 
  should 
  ever 
  be 
  met 
  with 
  in 
  the 
  open 
  sea. 
  No 
  instance 
  of 
  the 
  

   latter 
  defect 
  in 
  construction 
  has 
  yet 
  been 
  noted 
  in 
  the 
  instruments 
  of 
  

   the 
  Fish 
  Commission. 
  Up 
  to 
  the 
  present 
  time 
  the 
  propellers 
  of 
  the 
  new 
  

   Tanner 
  case, 
  although 
  not 
  so 
  well 
  protected 
  as 
  the 
  earlier 
  forms 
  against 
  

   lateral 
  currents, 
  have 
  not 
  yet 
  failed 
  to 
  answer 
  the 
  purpose 
  for 
  which 
  

   they 
  were 
  designed. 
  In 
  deep-sea 
  work 
  the 
  saving 
  in 
  time 
  by 
  dispensing 
  

   with 
  messengers 
  becomes 
  an 
  important 
  consideration. 
  

  

  Many 
  of 
  the 
  features 
  which 
  are 
  combined 
  in 
  the 
  modern 
  apparatus 
  

   for 
  observing 
  deep-sea 
  temperatures 
  arc 
  revivals 
  or 
  re-inventions 
  of 
  old 
  

   devices 
  which 
  had 
  been 
  once 
  used 
  and 
  forgotten. 
  Thus 
  the 
  outer 
  protect- 
  

  

  Fir.. 
  20. 
  — 
  Rpiulinu 
  Ions 
  for 
  the 
  Tamicr 
  

   thermometer 
  case. 
  

  

  