﻿430 
  Mr. 
  (J. 
  A. 
  Chant: 
  An 
  Experimental 
  Investigation 
  

  

  electrolytically 
  on 
  the 
  surface 
  of 
  a 
  metal 
  forming 
  a 
  resonator 
  

   a 
  shell 
  of 
  another 
  metal, 
  he 
  determined 
  what 
  thickness 
  he 
  

   must 
  add 
  in 
  order 
  that 
  the 
  resonator 
  should 
  behave 
  as 
  though 
  

   formed 
  of 
  the 
  second 
  metal. 
  He 
  used 
  an 
  electrometer 
  

   method, 
  and 
  his 
  results 
  are 
  shown 
  in 
  the 
  following 
  table 
  : 
  — 
  

  

  Table 
  II. 
  

  

  

  Original 
  

   Reading. 
  

  

  Final 
  

  

  Reading. 
  

  

  Thickness 
  of 
  

   Layer. 
  

  

  Copper 
  on 
  Iron 
  

  

  13-4 
  

  

  105 
  

  

  0-012 
  mm. 
  

  

  Zinc 
  on 
  Iron 
  

  

  13-4 
  

   100 
  

  

  71 
  

   80 
  

  

  0-016 
  „ 
  

   0012 
  „ 
  . 
  

  

  Zinc 
  on 
  Copper 
  

  

  Nickel 
  on 
  Copper 
  

  

  100 
  

  

  40 
  

  

  o-oio 
  „ 
  

  

  Cobalt 
  on 
  Copper 
  

  

  100 
  

  

  10 
  

  

  0-003 
  „ 
  

  

  Iron 
  on 
  Copper 
  

  

  100 
  

  

  10 
  

  

  0-003 
  „ 
  

  

  The 
  wave-length 
  used 
  by 
  Bjerknes 
  was 
  420 
  cms. 
  and 
  the 
  

   frequency, 
  therefore, 
  about 
  70 
  millions 
  per 
  second. 
  

  

  I 
  have 
  not 
  been 
  able 
  to 
  find 
  any 
  record 
  of 
  experiments 
  on 
  

   the 
  thickness 
  of 
  the 
  effective 
  portion 
  of 
  the 
  metal 
  of 
  an 
  

   oscillator 
  except 
  by 
  Preece 
  and 
  Righi. 
  

  

  The 
  former, 
  in 
  describing 
  experiments 
  made 
  in 
  conjunction 
  

   with 
  Marconi 
  on 
  signalling 
  without 
  wires, 
  says 
  * 
  : 
  — 
  

  

  " 
  The 
  distance 
  at 
  which 
  effects 
  are 
  produced, 
  with 
  such 
  

   rapid 
  oscillations 
  depends 
  chiefly 
  on 
  the 
  energy 
  of 
  the 
  dis- 
  

   charge 
  that 
  passes. 
  A 
  six-inch- 
  spark 
  coil 
  sufficed 
  through 
  

   1, 
  2, 
  3, 
  up 
  to 
  4 
  miles, 
  but 
  for 
  greater 
  distances 
  we 
  have 
  used 
  

   a 
  more 
  powerful 
  one 
  — 
  one 
  emitting 
  sparks 
  20 
  inches 
  long. 
  

   It 
  may 
  be 
  pointed 
  out 
  that 
  this 
  distance 
  increases 
  with 
  the 
  

   diameter 
  of 
  the 
  spheres 
  and 
  it 
  is 
  nearly 
  doubled 
  by 
  making 
  

   the 
  spheres 
  solid 
  instead 
  hollow." 
  

  

  He 
  used 
  the 
  regular 
  Eighi 
  oscillator 
  with 
  10 
  cm. 
  spheres 
  

   sparking 
  in 
  vaseline 
  oil, 
  from 
  which, 
  he 
  says, 
  there 
  were 
  

   emitted 
  waves 
  120 
  cms. 
  in 
  length, 
  with 
  a 
  frequency 
  of 
  

   250,000,000 
  per 
  second. 
  How 
  this 
  wave-length 
  was 
  deter- 
  

   mined 
  is 
  not 
  given. 
  

  

  Eighi 
  states 
  | 
  : 
  — 
  

  

  " 
  Finally 
  I 
  made 
  the 
  perhaps 
  unlooked-for 
  observation 
  

   that 
  an 
  oscillator 
  composed 
  of 
  hollow 
  spheres 
  is 
  less 
  effective 
  

   than 
  one 
  such 
  of 
  massive 
  spheres. 
  For 
  example, 
  when 
  the 
  

  

  * 
  Proc.Eoyal 
  Inst. 
  vol. 
  xv. 
  p. 
  472 
  (1897). 
  

  

  t 
  Righi, 
  Optik 
  der 
  elektrischen 
  Scfaoingungen, 
  pp. 
  14, 
  15. 
  

  

  