﻿346 
  Mr. 
  C. 
  Kinsley 
  on 
  the 
  Determination 
  of 
  

  

  and 
  the 
  constants 
  assumed 
  are 
  

  

  p 
  = 
  \ 
  saturation 
  for 
  the 
  different 
  temperatures, 
  

   B 
  = 
  760 
  mm. 
  of 
  mercury, 
  

   d 
  = 
  4 
  cm. 
  in 
  Table 
  II. 
  

  

  Since 
  d 
  is 
  assumed 
  to 
  be 
  4 
  cm. 
  in 
  Table 
  II. 
  the 
  quantity 
  

   to 
  be 
  added 
  to 
  / 
  will 
  be 
  0*41 
  d 
  = 
  l*64 
  for 
  every 
  note 
  when 
  a 
  

   tube 
  of 
  that 
  diameter 
  is 
  used. 
  

  

  For 
  other 
  tubes 
  the 
  correction 
  will 
  vary 
  for 
  different 
  Z's 
  

   due 
  to 
  the 
  changing 
  V 
  for 
  the 
  different 
  tubes. 
  Table 
  I. 
  

   gives 
  this 
  correction 
  for 
  all 
  tubes 
  apt 
  to 
  be 
  used. 
  

  

  The 
  error 
  in 
  reading 
  / 
  is 
  very 
  small 
  and 
  need 
  be 
  only 
  a 
  

   fraction 
  of 
  a 
  millimetre 
  in 
  any 
  case. 
  

  

  The 
  greatest 
  possible 
  error 
  due 
  to 
  the 
  assumption 
  of 
  

   J 
  saturation 
  will 
  be, 
  at 
  20° 
  C, 
  only 
  + 
  £ 
  per 
  cent, 
  when 
  p 
  is 
  

   100 
  per 
  cent, 
  of 
  saturation 
  and 
  —\ 
  per 
  cent, 
  for 
  zero 
  vapour 
  

   in 
  the 
  air. 
  

  

  Consequently 
  for 
  engineering 
  measurements 
  the 
  error 
  will 
  

   be 
  less 
  than 
  that 
  due 
  to 
  other 
  instruments, 
  and 
  so 
  may 
  be 
  

   neglected. 
  The 
  adjustment 
  for 
  maximum 
  resonance 
  can 
  be 
  

   made 
  with 
  greater 
  rapidity 
  than 
  that 
  with 
  which 
  a 
  Siemens 
  

   dynamometer 
  or 
  a 
  Thomson 
  balance 
  can 
  be 
  used. 
  This 
  makes 
  

   it 
  possible 
  to 
  use 
  an 
  ordinary 
  alternating 
  current 
  circuit 
  for 
  

   accurate 
  experimental 
  work. 
  

  

  The 
  tube 
  that 
  will 
  be 
  found 
  most 
  durable, 
  uniform, 
  and 
  

   convenient 
  will 
  be 
  a 
  drawn 
  brass 
  tube 
  4 
  cm. 
  in 
  diameter. 
  

  

  The 
  writer 
  has 
  very 
  carefully 
  compared 
  glass 
  and 
  drawn 
  

   brass 
  tubes, 
  and 
  finds 
  that 
  y 
  is 
  the 
  same 
  for 
  each. 
  He 
  has 
  

   also 
  measured 
  the 
  velocities 
  of 
  sound 
  using 
  a 
  chronograph 
  to 
  

   determine 
  n, 
  and 
  finds 
  that 
  the 
  value 
  for 
  a 
  already 
  given 
  can 
  

   be 
  used 
  without 
  sensible 
  error. 
  

  

  The 
  uniform 
  internal 
  diameter 
  of 
  the 
  brass 
  tube 
  makes 
  it 
  

   much 
  more 
  convenient 
  for 
  use, 
  as 
  a 
  dry 
  piston 
  can 
  be 
  employed. 
  

  

  The 
  natural 
  period 
  of 
  the 
  diaphragm 
  in 
  every 
  telephone 
  on 
  

   the 
  market 
  is 
  too 
  high 
  to 
  affect 
  in 
  any 
  sensible 
  way 
  the 
  

   harmonics 
  due 
  to 
  the 
  alternating 
  current. 
  

  

  A 
  number 
  of 
  other 
  methods 
  have 
  been 
  proposed 
  * 
  that 
  

   depend 
  on 
  the 
  resonance 
  of 
  iron 
  wire 
  or 
  strips 
  set 
  into 
  

   vibration 
  by 
  the 
  alternating 
  current. 
  

  

  Besides 
  the 
  impossibility 
  of 
  making, 
  with 
  either, 
  really 
  

   accurate 
  adjustments 
  for 
  maximum 
  resonance 
  — 
  which 
  is 
  

   independent 
  of 
  the 
  accuracy 
  of 
  the 
  gearing 
  — 
  it 
  is 
  necessary 
  

   to 
  standardize 
  the 
  instrument, 
  and 
  that 
  will 
  be 
  found 
  

   impossible 
  to 
  do 
  with 
  accuracy 
  except 
  in 
  a 
  very 
  well-equipped 
  

   laboratory. 
  

  

  * 
  Campbell, 
  Phil. 
  Mag., 
  Aug. 
  1896. 
  

  

  