﻿on 
  Electric 
  Waves 
  in 
  Short 
  Wire 
  Systems. 
  587 
  

  

  Hertzian 
  waves 
  is 
  developed, 
  which 
  is 
  more 
  sensitive 
  than 
  

   others 
  which 
  have 
  hitherto 
  been 
  used. 
  

  

  Apparatus. 
  

  

  The 
  arrangement 
  of 
  the 
  apparatus 
  used 
  in 
  these 
  experiments 
  

   is 
  shown 
  in 
  the 
  following 
  figure. 
  

  

  Fig. 
  1. 
  

  

  & 
  secondary 
  a 
  Y 
  — 
  — 
  b 
  

  

  cf 
  induction 
  /f 
  

  

  A 
  is 
  a 
  condenser 
  made 
  of 
  two 
  circular 
  brass 
  plates 
  30 
  cms. 
  

   in 
  diameter 
  and 
  0*853 
  cm. 
  thick, 
  the 
  inner 
  surfaces 
  being 
  

   scraped 
  plane. 
  One 
  plate 
  is 
  mounted 
  on 
  a 
  stand 
  which 
  can 
  

   be 
  moved 
  by 
  a 
  screw. 
  This 
  plate 
  can 
  thus 
  be 
  set 
  at 
  any 
  

   desired 
  distance 
  from 
  the 
  other 
  plate, 
  the 
  two 
  being 
  always 
  

   strictly 
  parallel. 
  The 
  plates 
  are 
  supported 
  by 
  stout 
  hard 
  

   rubber 
  tubes 
  in 
  which 
  are 
  placed 
  the 
  brass 
  lugs 
  aa. 
  Attached 
  

   to 
  these 
  lugs 
  are 
  tw 
  T 
  o 
  brass 
  wires 
  0'3 
  cm. 
  thick, 
  each 
  30 
  cms* 
  

   long, 
  bent 
  to 
  form 
  the 
  discharge 
  circuit 
  as 
  shown 
  in 
  the 
  

   figure, 
  the 
  sparks 
  taking 
  place 
  between 
  aluminium 
  spheres 
  

   1*1 
  cms. 
  in 
  diameter. 
  These 
  wires 
  are 
  in 
  a 
  horizontal 
  plane 
  ; 
  

   1*8 
  cms. 
  from 
  their 
  free 
  ends 
  they 
  are 
  bent 
  vertically 
  down- 
  

   wards, 
  the 
  aluminium 
  spheres 
  dipping 
  into 
  a 
  large 
  basin 
  of 
  

   paraffin 
  oil. 
  It 
  is 
  found 
  essential 
  for 
  uniformity 
  in 
  the 
  cha- 
  

   racter 
  of 
  the 
  spark 
  to 
  keep 
  the 
  oil 
  well 
  stirred. 
  To 
  enable 
  

   the 
  capacity 
  of 
  the 
  condenser 
  to 
  be 
  changed 
  without 
  altering 
  

   the 
  length 
  of 
  the 
  spark-gap 
  the 
  discharge 
  wire 
  attached 
  to 
  

   the 
  movable 
  plate 
  is 
  cut, 
  and 
  connexion 
  remade 
  through 
  a 
  

   little 
  pool 
  of 
  mercury. 
  The 
  capacity 
  of 
  the 
  condenser 
  circuit 
  

   can 
  thus 
  be 
  altered 
  without 
  changing 
  any 
  other 
  condition; 
  the 
  

   alteration 
  in 
  the 
  inductance 
  of 
  the 
  circuit 
  due 
  to 
  the 
  slight 
  

   change 
  in 
  its 
  length 
  through 
  the 
  pool 
  of 
  mercury 
  being 
  

   negligible. 
  

  

  Attached 
  to 
  the 
  condenser-plates, 
  but 
  carefully 
  insulated 
  

   from 
  them, 
  are 
  two 
  smaller 
  plates, 
  b 
  b, 
  8*8 
  cms. 
  in 
  diameter, 
  

   0'31 
  cm. 
  thick, 
  the 
  distance 
  between 
  them 
  and 
  the 
  condenser- 
  

   plates 
  being 
  0*75 
  cm. 
  To 
  these 
  plates 
  are 
  attached 
  brass 
  

   wires, 
  c 
  c, 
  0'04 
  cm. 
  in 
  diameter, 
  which 
  are 
  carried 
  30 
  cms. 
  

   apart 
  in 
  a 
  horizontal 
  plane 
  to 
  distances 
  varying 
  from 
  7 
  to 
  

   40 
  metres, 
  their 
  ends 
  being 
  attached 
  by 
  small 
  loops 
  to 
  

   insulated 
  supports. 
  

  

  