﻿Distribution 
  of 
  Energy 
  in 
  the 
  Spectra 
  of 
  Gases. 
  809 
  

  

  This 
  principle 
  was 
  explained 
  by 
  Clerk-Maxwell 
  in 
  his 
  

   ' 
  Treatise.' 
  

  

  For 
  purposes 
  of 
  comparison 
  the 
  sensitiveness 
  of 
  galvano- 
  

   meters 
  is 
  expressed 
  in 
  terms 
  of 
  certain 
  standards. 
  We 
  speak 
  

   of 
  the 
  Normal 
  Sensitiveness, 
  which 
  is 
  defined 
  as 
  follows 
  : 
  — 
  

  

  Let 
  i 
  — 
  current 
  in 
  amperes, 
  

   T 
  = 
  period 
  of 
  swing, 
  

   E= 
  resistance 
  of 
  galvanometer, 
  

   d 
  = 
  distance 
  of 
  scale 
  from 
  mirror, 
  in 
  metres, 
  

   s 
  = 
  scale 
  deflexion 
  in 
  mm., 
  

  

  then 
  the 
  normal 
  sensitiveness 
  is 
  

  

  S 
  = 
  s/d 
  . 
  10 
  2 
  /T 
  2 
  . 
  10- 
  6 
  /; 
  . 
  1/y/W. 
  

  

  Thus 
  it 
  is 
  the 
  deflexion 
  produced 
  at 
  a 
  distance 
  of 
  1 
  metre 
  

   when 
  a 
  current 
  of 
  10 
  ~ 
  6 
  ampere 
  is 
  passed 
  through 
  the 
  

   galvanometer, 
  the 
  time 
  of 
  swing 
  being 
  brought 
  up 
  to 
  

   10 
  sees, 
  and 
  the 
  resistance 
  being 
  1 
  ohm. 
  

  

  The 
  normal 
  sensitiveness 
  of 
  the 
  Paschen 
  galvanometer 
  is 
  

   4000, 
  and 
  the 
  whole 
  suspended 
  system 
  weighs 
  less 
  than 
  

  

  5 
  m 
  S" 
  

  

  A 
  further 
  description 
  of 
  the 
  instrument 
  is 
  to 
  be 
  found 
  in 
  

  

  Prof. 
  Paschen's 
  own 
  writings. 
  

  

  The 
  experiments 
  to 
  be 
  described 
  comprise 
  : 
  — 
  

  

  A. 
  An 
  examination 
  of 
  the 
  radiation 
  from 
  the 
  non-disruptive 
  

  

  discharge 
  in 
  hydrogen. 
  Owing 
  to 
  the 
  small 
  energy- 
  

   content 
  of 
  the 
  radiation, 
  these 
  were 
  confined 
  to 
  measure- 
  

   ments 
  of 
  the 
  total 
  visible 
  radiation, 
  as 
  transmitted 
  by 
  

   glass 
  lenses. 
  

  

  B. 
  Investigations 
  as 
  to 
  the 
  existence 
  of 
  a 
  displacement 
  of 
  

  

  energy 
  in 
  the 
  spectrum 
  with 
  increased 
  current-density. 
  

   For 
  these, 
  a 
  large 
  condenser 
  had 
  perforce 
  to 
  be 
  intro- 
  

   duced 
  into 
  the 
  circuit, 
  to 
  supply 
  the 
  necessary 
  energy. 
  

  

  In 
  some 
  of 
  the 
  experiments 
  a 
  spark-gap 
  was 
  also 
  

   introduced 
  in 
  series 
  with 
  the 
  discharge-tube, 
  thus 
  giving 
  

   a 
  still 
  further 
  increase 
  in 
  energy. 
  

   0. 
  An 
  examination 
  of 
  the 
  continuous 
  distribution 
  of 
  energy 
  

   in 
  the 
  same 
  disruptive 
  discharge 
  in 
  hydrogen 
  at 
  pressures 
  

   ranging 
  from 
  1 
  to 
  10 
  cm. 
  of 
  mercury. 
  

  

  A. 
  The 
  Radiation 
  from 
  the 
  non-Disrvptive 
  Discharge 
  

   in 
  Hydrogen. 
  

  

  For 
  the 
  measurement 
  of 
  the 
  current 
  in 
  the 
  discharge-tube 
  

   various 
  methods 
  were 
  tried. 
  The 
  electro-dynamometer 
  

   proved 
  unsuitable 
  for 
  the 
  reasons 
  mentioned. 
  An 
  attempt 
  

   was 
  also 
  made 
  to 
  set 
  up 
  a 
  thermo-couple 
  with 
  a 
  platinum 
  

  

  