﻿818 
  Mr. 
  H. 
  L. 
  P. 
  Jolly 
  on 
  the 
  

  

  measured 
  in 
  the 
  ordinary 
  way, 
  a 
  mean 
  deflexion 
  ma}>- 
  be 
  

   obtained 
  by 
  subtracting 
  the 
  mean 
  disturbance 
  from 
  the 
  mean 
  

   reading 
  with 
  the 
  shutter 
  open. 
  

  

  It 
  should 
  be 
  understood 
  that 
  it 
  is 
  only 
  when 
  the 
  condenser 
  

   discharges 
  are 
  used 
  that 
  such 
  observations 
  are 
  necessary, 
  for 
  

   the 
  steady 
  currents 
  produce 
  very 
  little 
  disturbing 
  effect 
  on 
  

   the 
  galvanometer. 
  In 
  the 
  following 
  experiments, 
  the 
  con- 
  

   denser 
  was 
  used, 
  and, 
  with 
  the 
  discharge-tube 
  close 
  up 
  to 
  the 
  

   slit 
  of 
  the 
  spectrometer, 
  mean 
  disturbances, 
  i. 
  e. 
  readings 
  with 
  

   the 
  shutter 
  closed, 
  were 
  always 
  observed 
  in 
  the 
  intervals 
  

   between 
  the 
  readings 
  with 
  the 
  shutter 
  open. 
  Later, 
  when 
  

   the 
  arrangement 
  of 
  the 
  apparatus 
  was 
  altered, 
  these 
  were 
  no 
  

   longer 
  necessary, 
  and 
  attention 
  was 
  concentrated 
  more 
  on 
  the 
  

   best 
  means 
  of 
  obtaining 
  a 
  consistent 
  set 
  of 
  readings 
  in 
  which 
  

   the 
  currents 
  had 
  not 
  varied. 
  

  

  As 
  regards 
  the 
  measurement 
  of 
  the 
  current 
  in 
  the 
  case 
  of 
  

   these 
  disruptive 
  discharges, 
  it 
  will 
  easily 
  be 
  understood 
  that 
  

   no 
  practicable 
  method 
  could 
  be 
  found. 
  

  

  When 
  the 
  current 
  rises 
  to 
  such 
  high 
  values 
  for 
  very 
  short 
  

   intervals 
  of 
  time, 
  the 
  electrometer 
  method 
  is 
  useless, 
  as 
  it 
  

   gives 
  no 
  indication 
  of 
  the 
  maximum 
  potential 
  difference 
  be- 
  

   tween 
  the 
  ends 
  of 
  the 
  potentiometer 
  resistance. 
  A 
  ballistic 
  

   method 
  is 
  also 
  impossible 
  owing 
  to 
  the 
  alternating 
  character 
  

   of 
  the 
  exciting 
  (primary) 
  current. 
  Since 
  we 
  are 
  only 
  looking 
  

   for 
  a 
  displacement 
  of 
  energy, 
  it 
  is 
  enough 
  to 
  establish 
  an 
  

   increase 
  or 
  decrease 
  of 
  the 
  current 
  when 
  certain 
  alterations 
  

   are 
  made, 
  and 
  to 
  see 
  whether 
  any 
  relative 
  changes 
  of 
  energy 
  

   in 
  the 
  spectrum 
  have 
  taken 
  place 
  when 
  the 
  current 
  has 
  

   varied. 
  The 
  method 
  of 
  the 
  rotating 
  mirror 
  described 
  above 
  

   is 
  unsuitable, 
  owing 
  to 
  the 
  difficulty 
  of 
  observing 
  the 
  length 
  

   of 
  the 
  somewhat 
  " 
  ghostly 
  " 
  peak 
  which 
  makes 
  its 
  appearance 
  

   when 
  the 
  disruptive 
  discharge 
  is 
  resorted 
  to. 
  

  

  The 
  mirror 
  was 
  therefore 
  used 
  first 
  of 
  all 
  to 
  establish 
  the 
  

   fact 
  that 
  when 
  the 
  terminals 
  of 
  the 
  primary 
  current 
  in 
  the 
  

   transformer 
  were 
  changed, 
  a 
  substantial 
  increase 
  in 
  the 
  dis- 
  

   charge 
  took 
  place. 
  The 
  subsidiary 
  discharge-tube 
  was 
  then 
  

   removed 
  from 
  the 
  circuit 
  and 
  the 
  currents 
  obtained 
  as 
  a 
  

   result 
  of 
  the 
  various 
  arrangements 
  of 
  the 
  transformer- 
  

   terminals 
  were 
  merely 
  designated 
  by 
  A, 
  B, 
  and 
  in 
  

   ascending 
  order 
  of 
  magnitude. 
  

  

  First 
  are 
  described 
  a 
  series 
  of 
  observations 
  intended 
  to 
  

   test 
  whether 
  there 
  is 
  any 
  displacement 
  of 
  the 
  energy 
  in 
  the 
  

   spectrum 
  when 
  the 
  strength 
  of 
  excitation 
  is 
  altered. 
  

  

  Table 
  II. 
  is 
  a 
  specimen 
  of 
  the 
  observations 
  at 
  one 
  pressure. 
  

   The 
  upper 
  half 
  refers 
  to 
  the 
  total 
  radiation 
  as 
  transmitted 
  by 
  

   the 
  spectroscope, 
  while 
  the 
  lower 
  represents 
  the 
  radiation 
  

  

  