﻿Electric 
  Waves 
  in' 
  Short 
  Wire 
  Systems, 
  

  

  599 
  

  

  between 
  the 
  plates. 
  The 
  position 
  of 
  the 
  bridge 
  was 
  so 
  chosen, 
  

   by 
  trial, 
  that 
  a 
  slight 
  change 
  in 
  the 
  distance 
  between 
  the 
  

   condenser-plates, 
  when 
  the 
  distance 
  was 
  about 
  0*6 
  cm., 
  

   resulted 
  in 
  the 
  greatest 
  change 
  in 
  the 
  deflexion 
  given 
  by 
  the 
  

   detector. 
  The 
  sensitiveness 
  was 
  such 
  that 
  a 
  change 
  of 
  O'l 
  cm. 
  

   in 
  the 
  distance 
  between 
  the 
  plates 
  caused 
  a 
  change 
  of 
  about 
  

   3 
  cms. 
  in 
  the 
  observed 
  deflexion. 
  An 
  equally 
  sensitive 
  

   arrangement 
  can 
  be 
  made 
  with 
  the 
  detector 
  in 
  the 
  secondary, 
  

   instead 
  of 
  in 
  the 
  primary 
  circuit. 
  

  

  It 
  must 
  be 
  remembered 
  that 
  any 
  change 
  in 
  the 
  spark 
  

   produces 
  a 
  considerable 
  change 
  in 
  the 
  deflexions, 
  so 
  great 
  

   precautions 
  have 
  to 
  be 
  taken 
  to 
  keep 
  the 
  character 
  of 
  the 
  

   spark 
  constant 
  during 
  a 
  set 
  of 
  observations. 
  This 
  was 
  

   effected 
  in 
  the 
  present 
  instance 
  by 
  not 
  allowing 
  the 
  spark- 
  

   gap 
  to 
  alter, 
  by 
  only 
  taking 
  single 
  sparks 
  for 
  each 
  observa- 
  

   tion, 
  and 
  so 
  minimizing 
  the 
  deterioration 
  of 
  the 
  surface 
  of 
  

   the 
  spark-knobs, 
  and 
  by 
  keeping 
  the 
  large 
  bath 
  of 
  paraffin 
  

   oil 
  through 
  which 
  the 
  sparks 
  passed 
  well 
  stirred. 
  

  

  Great 
  care 
  has 
  been 
  exercised 
  to 
  keep 
  the 
  plates 
  parallel 
  

   to 
  one 
  another, 
  and 
  the 
  distances 
  in 
  each 
  case 
  have 
  been 
  very 
  

   carefully 
  measured. 
  

  

  The 
  procedure 
  consists 
  in 
  finding 
  a 
  mean 
  deflexion 
  with 
  

   the 
  glass 
  between 
  the 
  plates, 
  then 
  with 
  the 
  glass 
  removed 
  

   obtaining 
  mean 
  deflexions 
  for 
  two 
  or 
  three 
  distances 
  with 
  air. 
  

  

  The 
  following 
  tables 
  giv.e 
  the 
  observations 
  which 
  have 
  been 
  

   made, 
  _a_ 
  being 
  the 
  distance 
  between 
  the 
  condenser-plates. 
  

   The 
  diameter 
  of 
  the 
  glass 
  disk 
  is 
  17*2 
  cms. 
  and 
  its 
  thickness 
  

   1*837 
  cms. 
  

  

  Table 
  III. 
  

  

  

  Glass 
  between 
  

  

  plates. 
  

  

  a= 
  1-837 
  cm. 
  

  

  Defls., 
  cms. 
  

  

  Air 
  between 
  

  

  plates. 
  

  

  a 
  =0-554 
  cm. 
  

  

  Defls., 
  cms. 
  

  

  Air 
  between 
  

  

  plates. 
  

  

  a 
  =0-578 
  cm. 
  

  

  Defls., 
  cms. 
  

  

  Air 
  between 
  

  

  plates. 
  

   a 
  =0*602 
  cm. 
  

   Defls., 
  cms. 
  

  

  Dec. 
  18th, 
  

   1901. 
  

  

  17-3 
  

   17-4 
  

  

  16-8 
  

  

  167 
  

   174 
  

  

  18-0 
  

   17-4 
  

  

  

  176 
  

  

  16-9 
  

  

  18-2 
  

  

  174 
  

  

  

  171 
  

  

  16-6 
  

  

  17*0 
  

  

  

  - 
  

  

  17-4 
  

  

  

  17-4 
  

  

  

  Mean 
  

  

  ... 
  17-36 
  16-77 
  1734 
  

  

  17*60 
  

  

  a 
  =0-578 
  cir 
  

   a= 
  1-837 
  cm 
  

  

  is. 
  with 
  air 
  gives 
  the 
  same 
  deflexion 
  as 
  

  

  s. 
  with 
  glass 
  between 
  the 
  plates. 
  Temp. 
  27 
  

  

  °-8-28°-5C. 
  

  

  