﻿594 
  

  

  Messrs. 
  Cameron 
  and 
  Oettinger 
  on 
  Electromotive 
  

  

  is 
  consequently 
  over-estimated, 
  and 
  we 
  are 
  by 
  no 
  means 
  

   certain 
  that 
  this 
  over-estimation 
  produces 
  merely 
  an 
  error 
  

   consisting 
  of 
  an 
  approximately 
  constant 
  factor. 
  When 
  these 
  

   considerations 
  are 
  borne 
  in 
  mind 
  the 
  following 
  figures 
  will 
  

   not 
  seem 
  imfit 
  to 
  support 
  the 
  formula: 
  — 
  * 
  

  

  A 
  are 
  the 
  observed 
  pressures 
  between 
  the 
  ends 
  of 
  the 
  tube 
  

   corrected 
  for 
  the 
  water 
  column 
  in 
  the 
  glass 
  containiug-vessel, 
  

   B 
  are 
  the 
  pressures 
  calculated 
  to 
  exist 
  betw^een 
  the 
  tw^o 
  

   electrodes 
  under 
  consideration, 
  from 
  the 
  law 
  that 
  the 
  fall 
  in 
  

   pressure 
  is 
  proportional 
  to 
  the 
  length 
  along 
  the 
  tube. 
  During 
  

   the 
  experiment, 
  which 
  lasted 
  an 
  hour, 
  temperature 
  varied 
  

   between 
  18° 
  and 
  19° 
  C. 
  The 
  sensibility 
  of 
  the 
  electrometer 
  

   was 
  such 
  that 
  1 
  cm. 
  on 
  the 
  reading 
  scale 
  corresponded 
  to 
  

   0-05 
  volt. 
  

  

  A 
  

  

  Portion 
  of 
  

  

  B 
  

  

  E.M.F. 
  

  

  E.M.F./B. 
  

  

  mm. 
  Hg. 
  

  

  tube 
  taken. 
  

  

  mm. 
  Hg. 
  

  

  volt. 
  

  

  380-9 
  

  

  a/3 
  

  

  87-6 
  

  

  + 
  0-.593 
  

  

  6-76x10-3 
  

  

  381-3 
  

  

  ay 
  

  

  224-5 
  

  

  1-400 
  

  

  6-23 
  

  

  382-2 
  

  

  aO 
  

  

  321-3 
  

  

  1-914 
  

  

  5-96 
  

  

  380-7 
  

  

  /3r 
  

  

  136-8 
  

  

  0-815 
  

  

  5 
  96 
  

  

  382 
  

  

  /io 
  

  

  233-4 
  

  

  1-307 
  

  

  5-60 
  

  

  381-6 
  

  

  yd 
  

  

  96-1 
  

  

  0-490 
  

  

  510 
  

  

  249-5 
  

  

  a^ 
  

  

  57-4 
  

  

  0-398 
  

  

  6-94 
  

  

  249-1 
  

  

  ay 
  

  

  146-7 
  

  

  0-971 
  

  

  6-62 
  1 
  

  

  248-3 
  

  

  ao 
  

  

  208-7 
  

  

  1-351 
  

  

  6-47 
  

  

  249-8 
  

  

  fir 
  

  

  89-8 
  

  

  0-571 
  

  

  6-38 
  

  

  249-6 
  

  

  l3d 
  

  

  152-6 
  

  

  0-959 
  

  

  6-27 
  1 
  

  

  575-0 
  

  

  a(5 
  

  

  132-2 
  

  

  0-833 
  

  

  6-30 
  

  

  594-4 
  

  

  ay 
  

  

  3500 
  

  

  2-100 
  

  

  600 
  i 
  

  

  567-7 
  

  

  ^y 
  

  

  204-0 
  

  

  1-197 
  

  

  5-87 
  , 
  

  

  Since 
  when 
  water 
  is 
  stored 
  in 
  a 
  glass 
  vessel 
  and 
  used 
  con- 
  

   tinuously 
  in 
  an 
  experiment 
  of 
  some 
  duration, 
  there 
  arises 
  the 
  

   possibility 
  that 
  small 
  changes 
  may 
  take 
  place 
  in 
  the 
  con- 
  

   ductivity 
  of 
  the 
  water, 
  to 
  avoid 
  such 
  an 
  error 
  experiments 
  

   were 
  carried 
  out 
  with 
  very 
  dilute 
  solutions 
  of 
  potassium 
  

   chloride. 
  Of 
  these 
  the 
  following 
  are 
  typical 
  : 
  — 
  

  

  Experiment 
  2. 
  To 
  test 
  the 
  effect 
  of 
  different 
  i^ressures 
  and 
  

   duration 
  of 
  time. 
  — 
  A 
  new 
  tube 
  was 
  employed, 
  containing 
  two 
  

   electrodes, 
  242 
  mm. 
  apart. 
  The 
  whole 
  length 
  of 
  the 
  tube, 
  ex- 
  

   cluding 
  the 
  electrode 
  spaces, 
  was 
  470 
  mm.t, 
  and 
  its 
  diameter 
  

  

  * 
  It 
  may 
  also 
  be 
  pointed 
  out 
  that 
  the 
  diameter 
  of 
  the 
  tube 
  was 
  perhaps 
  

   a 
  little 
  greater 
  than 
  those 
  which 
  strictly 
  obey 
  Poiseuille's 
  law. 
  

   I 
  Each 
  electrode 
  space 
  was 
  5 
  mm. 
  in 
  length. 
  

  

  