﻿256 
  Pierce 
  — 
  Application 
  of 
  the 
  Radio- 
  Micrometer 
  

  

  However, 
  when 
  the 
  instrument 
  was 
  set 
  up, 
  

  

  it 
  was 
  at 
  first 
  

   coming 
  direct 
  

  

  violently 
  influenced 
  by 
  an 
  electrostatic 
  action 
  

   from 
  the 
  oscillator. 
  This 
  proved 
  to 
  be 
  due 
  to 
  a 
  small 
  conden 
  

   ser 
  that 
  had 
  been 
  placed 
  in 
  series 
  with 
  the 
  secondary 
  of 
  the 
  

   induction 
  coil 
  for 
  the 
  purpose 
  of 
  diminishing 
  the 
  arc 
  at 
  the 
  

   oscillator. 
  By 
  removing 
  this 
  capacity, 
  and 
  by 
  coating 
  over 
  

   with 
  tin 
  foil 
  the 
  wooden 
  cover 
  of 
  the 
  top 
  part 
  of 
  the 
  receiving 
  

   apparatus, 
  a 
  recurrence 
  of 
  this 
  disturbance 
  has 
  been 
  prevented. 
  

   The 
  Oscillator. 
  — 
  Reference 
  is 
  made 
  to 
  

   fig. 
  5. 
  Two 
  platinum 
  cylinders, 
  0, 
  tipped 
  

   with 
  pieces 
  of 
  iridium, 
  are 
  fused 
  into 
  the 
  

   ends 
  of 
  small 
  tubes 
  of 
  thermometer 
  glass, 
  

   t. 
  These 
  thermometer 
  tubes 
  are 
  passed 
  

   through 
  the 
  rubber 
  stoppers 
  of 
  a 
  larger 
  

   tube, 
  T, 
  for 
  holding 
  oil. 
  The 
  larger 
  tube 
  

   has 
  a 
  diameter 
  of 
  2 
  cm 
  , 
  and 
  by 
  wooden 
  

   braces 
  is 
  held 
  at 
  the 
  axis 
  of 
  a 
  parabolic 
  

   cylindrical 
  reflector 
  of 
  the 
  same 
  dimen- 
  

   sions 
  as 
  that 
  of 
  the 
  resonator. 
  The 
  dis- 
  

   tance 
  between 
  the 
  platinum 
  cylinders 
  of 
  

   the 
  oscillator 
  can 
  be 
  adjusted 
  by 
  means 
  of 
  

   the 
  micrometer 
  screw, 
  s. 
  Into 
  the 
  

   smaller 
  tubes 
  are 
  brought 
  two 
  small 
  plati- 
  

   num 
  wires 
  connected 
  by 
  copper 
  leads 
  to 
  

   the 
  secondary 
  of 
  an 
  induction 
  coil 
  of 
  

   medium 
  size. 
  These 
  wires 
  are 
  separated 
  

   by 
  spark 
  gaps, 
  h, 
  from 
  the 
  platinum 
  cylin- 
  

  

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  * 
  

  

  \* 
  ^ 
  /////// 
  ^y 
  The 
  spark-gaps, 
  b, 
  are 
  about 
  2 
  mm 
  long, 
  

  

  and 
  serve 
  to 
  isolate 
  the 
  platinum 
  cylinders, 
  

   seems 
  to 
  depend 
  in 
  a 
  slight 
  degree 
  the 
  

   period 
  of 
  the 
  oscillation, 
  which 
  by 
  their 
  adjustment 
  can 
  

   be 
  made 
  approximately 
  equal 
  to 
  that 
  of 
  the 
  resonator. 
  The 
  

   spark 
  in 
  oil, 
  a, 
  must 
  be 
  very 
  short 
  to 
  prevent 
  the 
  damp- 
  

   ing 
  out 
  of 
  the 
  oscillations. 
  The 
  wearing 
  away 
  of 
  the 
  ter- 
  

   minals 
  at 
  this 
  gap 
  is 
  a 
  source 
  of 
  great 
  annoyance 
  by 
  changing 
  

   this 
  damping 
  factor, 
  and 
  consequently 
  changing 
  the 
  quan- 
  

   tity 
  of 
  energy 
  radiated 
  as 
  electric 
  waves. 
  Platinum 
  is 
  the 
  

   only 
  metal 
  that 
  I 
  could 
  fuse 
  into 
  the 
  glass 
  tubes 
  that 
  would 
  

   not 
  break 
  the 
  tubes 
  under 
  the 
  heat 
  of 
  the 
  spark, 
  and 
  platinum 
  

   was 
  found 
  to 
  wear 
  away 
  very 
  rapidly, 
  presumably 
  on 
  account 
  

   of 
  the 
  action 
  on 
  it 
  of 
  the 
  hydrogen 
  freed 
  by 
  the 
  decomposition 
  

   of 
  the 
  oil. 
  I 
  have 
  attempted 
  to 
  diminish 
  this 
  destruction 
  of 
  

   the 
  oscillators 
  by 
  tipping 
  them 
  with 
  pieces 
  of 
  iridium 
  fused 
  

   on 
  with 
  copper 
  as 
  a 
  solder. 
  The 
  iridium 
  disappears 
  much 
  

   more 
  slowly 
  than 
  the 
  bare 
  platinum. 
  Other 
  oscillators 
  I 
  have 
  

   tipped 
  with 
  silver, 
  but 
  the 
  iridium 
  serves 
  better. 
  However, 
  

  

  Upon 
  their 
  

  

  length 
  

  

  