﻿G. 
  Y. 
  Maclean 
  — 
  Velocity 
  of 
  Electric 
  Waves 
  in 
  Air. 
  9 
  

  

  nevertheless 
  it 
  successfully 
  eliminated 
  the 
  disturbance, 
  wUicli 
  

   was 
  very 
  detrimental 
  to 
  the 
  accuracy 
  of 
  the 
  observed 
  readings 
  

   of 
  the 
  needle. 
  All 
  the 
  measurements 
  herein 
  given 
  were 
  taken 
  

   by 
  the 
  above 
  method. 
  The 
  readings 
  thus 
  taken 
  are 
  very 
  small, 
  

   the 
  highest 
  not 
  exceeding 
  three 
  small 
  divisions 
  of 
  the 
  Mille- 
  

   Ampere 
  meter 
  scale 
  ; 
  but 
  they 
  are 
  otherwise 
  perfectly 
  regular, 
  

   showing 
  a 
  distinct 
  increase 
  and 
  decrease 
  with 
  change 
  of 
  posi- 
  

   tion 
  of 
  the 
  coherer 
  from 
  the 
  reflector. 
  Readings 
  can 
  be 
  taken 
  

   with 
  a 
  fair 
  degree 
  of 
  rapidity, 
  when 
  all 
  conditions 
  are 
  favor- 
  

   able 
  ; 
  as 
  many 
  as 
  forty 
  having 
  been 
  taken 
  in 
  three 
  hours. 
  

   Measurements 
  were 
  begun 
  as 
  near 
  the 
  reflector 
  as 
  possible 
  

   and 
  continued 
  towards 
  the 
  oscillator. 
  The 
  first 
  zero 
  reading 
  

   was 
  located 
  at 
  1-1500 
  m. 
  f^'om 
  the 
  reflector 
  and 
  the 
  first 
  maxi- 
  

   iTQum 
  at 
  2-6290 
  m. 
  from 
  the 
  reflector. 
  The 
  second 
  zero 
  was 
  

   found 
  to 
  be 
  at 
  4:*10T5 
  m. 
  and 
  the 
  second 
  maximum 
  at 
  5*5863 
  m., 
  

   while 
  the 
  third 
  zero 
  was 
  at 
  T"0650 
  m. 
  from 
  the 
  reflector. 
  We, 
  

   therefore, 
  have 
  a 
  distance 
  of 
  1*4790 
  m. 
  between 
  the 
  first 
  anti- 
  

   node 
  and 
  node, 
  1*4785 
  m. 
  between 
  the 
  first 
  node 
  and 
  second 
  

   anti-node, 
  1*4788 
  m. 
  between 
  the 
  second 
  anti-node 
  and 
  second 
  

   node 
  and 
  1*4787 
  m. 
  between 
  the 
  second 
  node 
  and 
  third 
  anti- 
  

   node. 
  This 
  gives 
  us 
  a 
  distance 
  of 
  2*9575 
  m. 
  between 
  the 
  first 
  

   and 
  second 
  anti-nodes 
  and 
  also 
  2*9575 
  m. 
  between 
  the 
  second 
  

   and 
  third 
  anti-nodes 
  ; 
  that 
  is 
  to 
  say, 
  the 
  half 
  wave-length 
  is 
  

   2*9575 
  m., 
  or 
  the 
  wave-length 
  is 
  5*915 
  m. 
  Accordingly 
  there 
  

   should 
  be 
  a 
  node 
  at 
  •3290 
  m. 
  back 
  of 
  the 
  reflector. 
  jNo 
  results 
  

   are 
  here 
  recorded 
  of 
  the 
  observations 
  made 
  nearer 
  to 
  the 
  oscil- 
  

   lator 
  than 
  a 
  full 
  wave-length. 
  For 
  as 
  one 
  approaches 
  the 
  

   oscillator 
  in 
  this 
  distance, 
  though 
  the 
  readings 
  show 
  increases 
  

   and 
  decreases 
  yet 
  no 
  actual 
  zero 
  reading 
  was 
  located. 
  More- 
  

   over 
  in 
  this 
  space, 
  the 
  phenomenon 
  above 
  described 
  was 
  very 
  

   strongly 
  active 
  and 
  diflicult 
  to 
  overcome. 
  The 
  measurements 
  

   below 
  tabulated 
  were 
  all 
  taken 
  in 
  the 
  space 
  at 
  least 
  a 
  wave 
  

   length 
  distant 
  from 
  the 
  oscillator. 
  The 
  following 
  are 
  the 
  

   results 
  of 
  nearly 
  500 
  observations. 
  The 
  first 
  column 
  gives 
  the 
  

   distances 
  of 
  the 
  coherer 
  from 
  the 
  refiector, 
  columns 
  two 
  and 
  

   three 
  give 
  the 
  readings 
  on 
  the 
  Mille-Ampere 
  meter 
  scale 
  for 
  

   the 
  first 
  maximum 
  reading 
  and 
  the 
  increased 
  reading, 
  while 
  

   column 
  three 
  shows 
  the 
  increase 
  in 
  the 
  readings 
  due 
  to 
  the 
  

   passage 
  of 
  the 
  electric 
  waves. 
  Five 
  measurements 
  at 
  least 
  were 
  

   taken 
  at 
  each 
  point 
  of 
  observation. 
  Owing 
  to 
  the 
  space 
  all 
  

   the 
  readings 
  occupy, 
  only 
  a 
  few 
  of 
  them 
  are 
  here 
  given. 
  The 
  

   general 
  nature 
  of 
  the 
  rest 
  of 
  the 
  readings 
  can 
  be 
  seen 
  from 
  the 
  

   curve 
  (p. 
  12). 
  

  

  