﻿on 
  Electric 
  Waves 
  in 
  Short 
  Wire 
  Systems. 
  589 
  

  

  due 
  to 
  the 
  presence 
  on 
  the 
  outer 
  sides 
  of 
  the 
  condenser-plates, 
  

   but 
  near 
  to 
  their 
  edges, 
  of 
  eight 
  small 
  brass 
  screws 
  employed 
  

   in 
  holding 
  hard 
  rubber 
  brackets 
  which 
  were 
  used 
  for 
  adjust- 
  

   ing 
  the 
  plates 
  parallel 
  to 
  one 
  another. 
  These 
  screws 
  were 
  

   subsequently 
  dispensed 
  with. 
  

  

  In 
  some 
  of 
  the 
  experiments, 
  a 
  circular 
  glass 
  disk, 
  1*837 
  cms. 
  

   thick 
  and 
  17*2 
  cms. 
  in 
  diameter, 
  was 
  mounted 
  between 
  the 
  

   condenser-plates, 
  coaxial 
  with 
  them^ 
  the 
  plates 
  being 
  in 
  con- 
  

   tact 
  with 
  the 
  glass 
  on 
  either 
  side. 
  The 
  specific 
  inductive 
  

   capacity 
  of 
  the 
  glass 
  as 
  determined 
  later 
  is 
  7*8. 
  The 
  formula 
  

   for 
  calculating 
  the 
  capacity 
  of 
  the 
  condenser 
  under 
  these 
  

   circumstances 
  is 
  given 
  in 
  the 
  discussion 
  of 
  the 
  specific 
  in- 
  

   ductive 
  capacity 
  measurements. 
  To 
  this 
  calculated 
  capacity 
  

   must 
  be 
  added 
  the 
  small 
  corrections 
  for 
  screws 
  and 
  discharge 
  

   circuit 
  as 
  found 
  previously. 
  In 
  other 
  experiments, 
  a 
  glass 
  

   plate 
  of 
  the 
  same 
  thickness, 
  but 
  35*5 
  cms. 
  in 
  diameter, 
  was 
  

   placed 
  between 
  the 
  condenser-plates, 
  the 
  plates 
  touching 
  the 
  

   glass 
  as 
  before. 
  The 
  glass 
  plate 
  being 
  larger 
  in 
  diameter 
  

   than 
  the 
  brass 
  plates, 
  it 
  is 
  impossible 
  to 
  evaluate 
  the 
  edge 
  

   correction 
  to 
  the 
  capacity. 
  All 
  that 
  need 
  be 
  said, 
  however, 
  

  

  Kr 
  2 
  

   is 
  that 
  the 
  capacity 
  is 
  greater 
  than 
  — 
  -f 
  the 
  edge 
  correction 
  

  

  in 
  air, 
  K 
  being 
  the 
  specific 
  inductive 
  capacity 
  of 
  the 
  glass 
  

   7-8, 
  r 
  the 
  radius 
  of 
  the 
  brass 
  plates 
  and 
  a 
  the 
  distance 
  between 
  

   them. 
  

  

  The 
  formula 
  which 
  has 
  been 
  used 
  for 
  calculating 
  the 
  induc- 
  

  

  (8/ 
  \ 
  

  

  logg— 
  - 
  — 
  2 
  ), 
  I 
  being 
  

  

  the 
  length 
  of 
  the 
  circuit 
  assumed 
  circular, 
  and 
  d 
  the 
  diameter 
  

   of 
  the 
  wires. 
  The 
  circuit 
  is 
  made 
  up 
  of 
  a 
  pair 
  of 
  thick 
  brass 
  

   wires 
  0*3 
  cm. 
  in 
  diameter 
  and 
  of 
  total 
  length 
  60 
  cms., 
  and 
  a 
  

   pair 
  of 
  stout 
  brass 
  lugs 
  connected 
  to 
  the 
  condenser-plates, 
  of 
  

   total 
  length 
  4*5 
  cms. 
  and 
  1*2 
  cms. 
  in 
  diameter, 
  into 
  which 
  the 
  

   discharge-wires 
  are 
  fastened. 
  The 
  inductance 
  has 
  been 
  calcu- 
  

   lated 
  on 
  the 
  assumption 
  that 
  the 
  total 
  length 
  of 
  the 
  circuit 
  is 
  

   64" 
  5 
  cms., 
  the 
  extra 
  diameter 
  of 
  the 
  lugs 
  being 
  neglected. 
  

  

  The 
  wave-length 
  in 
  air 
  of 
  the 
  condenser 
  radiation 
  has 
  been 
  

   found 
  by 
  the 
  formula 
  X=2tt 
  VL.C, 
  C 
  being 
  in 
  electrostatic 
  

   units. 
  From 
  a 
  resonance 
  experiment, 
  to 
  be 
  described 
  later, 
  

   the 
  calculated 
  wave-length 
  is 
  found 
  to 
  be 
  about 
  5 
  per 
  cent, 
  

   too 
  large, 
  and 
  other 
  evidence 
  points 
  to 
  the 
  same 
  conclusion. 
  

   The 
  calculated 
  values 
  have 
  therefore 
  been 
  reduced 
  by 
  this 
  

   amount. 
  For 
  the 
  present 
  purpose, 
  only 
  approximate 
  values 
  

   are 
  required. 
  

  

  Phil. 
  Mag. 
  S. 
  6. 
  Vol. 
  3. 
  No. 
  18. 
  June 
  1902. 
  2 
  R 
  

  

  