﻿Ionization 
  and 
  Wireless 
  Telegraphy 
  * 
  

  

  573 
  

  

  thus 
  in 
  parallel 
  with 
  the 
  same, 
  was 
  a 
  special 
  zinc-plate 
  air- 
  

   condenser 
  ZZ. 
  

  

  Fig. 
  4. 
  — 
  Final 
  Arrangement. 
  

  

  This 
  consists 
  of" 
  two 
  sets 
  of 
  plates 
  — 
  one 
  of 
  eight, 
  the 
  other 
  

   of 
  seven, 
  each 
  plate 
  being 
  30*4 
  cm. 
  diameter 
  and 
  0*2 
  cm. 
  

   thick. 
  The 
  inner 
  surfaces 
  of 
  the 
  plates 
  in 
  each 
  set 
  were 
  

   1-2 
  cm. 
  apart, 
  leaving 
  air-spaces 
  of 
  0'5 
  cm. 
  between 
  the 
  

   plates 
  when 
  in 
  mesh. 
  The 
  plates 
  were 
  separated 
  by 
  wooden 
  

   distance-pieces. 
  Good 
  connexion 
  is 
  ensured 
  by 
  pieces 
  of 
  

   tinfoil 
  and 
  a 
  metal 
  rod 
  by 
  which 
  the 
  plates 
  are 
  held 
  securely. 
  

   By 
  sliding 
  the 
  plates 
  of 
  one 
  set 
  between 
  those 
  of 
  the 
  other 
  a 
  

   condenser 
  of 
  variable 
  capacity 
  could 
  be 
  formed. 
  Throughout 
  

   the 
  work 
  the 
  maximum 
  capacity 
  was 
  used 
  ; 
  the 
  plates 
  were 
  

   placed 
  on 
  clean, 
  dry 
  blocks 
  of 
  wax, 
  and 
  two 
  bridges 
  of 
  wax 
  

   were 
  put 
  across 
  them 
  to 
  afford 
  greater 
  rigidity. 
  

  

  As 
  a 
  more 
  sensitive 
  detector 
  than 
  the 
  usual 
  neon 
  tube 
  a 
  

   special 
  electrometer 
  was 
  then 
  used. 
  This 
  was 
  of 
  the 
  form 
  

   used 
  by 
  J. 
  R. 
  von 
  Geitler 
  and 
  by 
  one 
  of 
  the 
  present 
  writers 
  

   when 
  working 
  under 
  Hertz 
  in 
  Bonn. 
  The 
  needle 
  is 
  of 
  alu- 
  

   minium 
  and 
  carries 
  a 
  small 
  plane 
  mirror 
  for 
  reading 
  the 
  

   deflexions, 
  and 
  a 
  tiny 
  magnetic 
  needle 
  for 
  control. 
  In 
  the 
  

   horizontal 
  section 
  shown 
  in 
  fig. 
  4, 
  N" 
  is 
  the 
  aluminium 
  

   needle 
  in 
  a 
  vertical 
  plane 
  suspended 
  by 
  a 
  quartz 
  fibre 
  ; 
  

   D 
  D 
  are 
  two 
  metal 
  disks 
  equal 
  in 
  size 
  to 
  the 
  circular 
  ends 
  

   of 
  the 
  needle 
  and 
  attached 
  to 
  the 
  inside 
  of 
  the 
  wooden 
  case. 
  

   On 
  to 
  the 
  projecting 
  rods 
  from 
  these 
  disks 
  were 
  soldered 
  the 
  

   wires 
  from 
  the 
  condenser 
  terminals. 
  The 
  needle 
  is 
  con- 
  

   trolled 
  by 
  a 
  magnet 
  M, 
  and 
  the 
  deflexions 
  observed 
  by 
  means 
  

  

  