﻿6 
  G. 
  Y. 
  Maclean 
  — 
  Velocity 
  of 
  Electric 
  Waves 
  in 
  Air. 
  

  

  sparking 
  at 
  the 
  oscillator 
  was 
  much 
  altered, 
  too 
  much 
  water 
  

   acting 
  like 
  too 
  little. 
  Wires 
  ran 
  from 
  the 
  break 
  to 
  the 
  Ruhm- 
  

   korff 
  coil 
  and 
  also 
  to 
  a 
  key 
  at 
  the 
  coherer 
  carriage. 
  Thus 
  from 
  

   the 
  coherer 
  carriage 
  one 
  could 
  control 
  both 
  the 
  coherer 
  and 
  

   oscillator 
  circuits. 
  

  

  The 
  various 
  parts 
  of 
  the 
  oscillator 
  circuit 
  are 
  shown 
  in 
  

   Plate 
  I. 
  

  

  The 
  motor 
  and 
  break 
  were 
  enclosed 
  in 
  a 
  double 
  box, 
  the 
  

   space 
  between 
  the 
  two 
  boxes 
  being 
  packed 
  with 
  felt. 
  This 
  

   was 
  done 
  in 
  order 
  to 
  deaden 
  the 
  noise 
  of 
  the 
  motor 
  and 
  prim- 
  

   ary 
  sparking. 
  Such 
  a 
  proceeding 
  is 
  not 
  essential 
  to 
  the 
  good 
  

   working 
  of 
  the 
  coherer, 
  but 
  it 
  enables 
  one 
  to 
  detect 
  at 
  once 
  by 
  

   the 
  ear 
  any 
  variation 
  in 
  the 
  secondary 
  sparking. 
  It 
  thus 
  

   leaves 
  the 
  eyes 
  free 
  to 
  observe 
  the 
  movements 
  of 
  the 
  Mi 
  lie 
  - 
  

   Ampere 
  meter 
  needle. 
  One 
  soon 
  became 
  accustomed 
  to 
  the 
  

   characteristic 
  crackling 
  sound 
  of 
  the 
  kind 
  of 
  sparks 
  required 
  

   and 
  accordingly 
  hardly 
  ever 
  needed 
  to 
  look 
  at 
  the 
  oscillator. 
  

   The 
  sparks 
  produced 
  at 
  the 
  oscillator 
  must 
  be 
  continuous 
  and 
  

   always 
  the 
  same, 
  otherwise 
  the 
  waves 
  set 
  up 
  will 
  differ 
  from 
  

   each 
  other 
  and 
  consequently 
  the 
  Mille-Ampere 
  meter 
  needle 
  

   readings 
  will 
  vary 
  so 
  irregularly 
  as 
  to 
  be 
  absolutely 
  worthless. 
  

   Sparks 
  of 
  the 
  same 
  nature 
  must 
  therefore 
  be 
  produced 
  at 
  all 
  

   times 
  during 
  the 
  experiment. 
  This 
  is 
  rendered 
  possible 
  by 
  

   the 
  employment 
  of 
  the 
  continuous 
  stream 
  of 
  water 
  over 
  the 
  

   surface 
  of 
  the 
  mercury 
  in 
  the 
  mercury 
  cup 
  of 
  the 
  break. 
  

  

  The 
  coherer 
  and 
  its 
  capacity 
  were 
  mounted 
  upon 
  a 
  stand, 
  car- 
  

   ried 
  upon 
  a 
  carriage 
  which 
  could 
  be 
  easily 
  moved 
  along 
  a 
  grad- 
  

   uated 
  track. 
  It 
  was 
  possible 
  to 
  make 
  a 
  change 
  in 
  position 
  of 
  the 
  

   carriage 
  as 
  small 
  as 
  '25 
  mm. 
  To 
  the 
  side 
  of 
  the 
  carriage 
  was 
  

   firmly 
  secured 
  a 
  shelf 
  which 
  supported 
  the 
  keys 
  of 
  the 
  two 
  cir- 
  

   cuits, 
  the 
  shunt 
  resistance 
  and 
  the 
  Mille-Ampere-meter. 
  The 
  

   lower 
  part 
  of 
  the 
  carriage 
  held 
  the 
  battery 
  and 
  its 
  resistance 
  

   box. 
  

  

  If 
  the 
  coherer 
  be 
  placed 
  in 
  any 
  part 
  of 
  the 
  room, 
  it 
  

   responds 
  to 
  the 
  sparking 
  of 
  the 
  oscilhitor, 
  but 
  in 
  some 
  posi- 
  

   tions 
  more 
  strongly 
  than 
  in 
  others. 
  It 
  thus 
  appeared 
  desirable 
  

   to 
  place 
  the 
  oscillator 
  within 
  a 
  completely 
  closed 
  metal 
  box. 
  

   with 
  a 
  window 
  in 
  its 
  front 
  side. 
  This 
  proved 
  beneficial, 
  since 
  

   it 
  caused 
  the 
  waves 
  to 
  be 
  less 
  scattered 
  at 
  the 
  instant 
  of 
  leaving 
  

   the 
  oscillator, 
  confining 
  them 
  more 
  to 
  that 
  region 
  of 
  the 
  room 
  

   where 
  the 
  experiment 
  is 
  conducted, 
  than 
  elsewhere. 
  The 
  

   metal 
  box 
  then 
  acts, 
  as 
  it 
  were, 
  like 
  a 
  megaphone. 
  The 
  front 
  

   of 
  the 
  box 
  was 
  on 
  hinges 
  and 
  could 
  be 
  left 
  open 
  at 
  pleasure. 
  

   The 
  inside 
  of 
  the 
  metal 
  box 
  was 
  put 
  into 
  metal 
  connection 
  

   with 
  the 
  gas 
  pipes 
  of 
  the 
  room. 
  At 
  one 
  end 
  of 
  the 
  room 
  was 
  

   placed 
  the 
  oscillator, 
  while 
  at 
  the 
  opposite 
  end 
  was 
  fixed 
  a 
  

   metal 
  refiector 
  which 
  was 
  connected 
  by 
  wires 
  to 
  gas 
  pipes 
  and 
  

  

  