﻿Prof. 
  D. 
  N. 
  Mallik 
  on 
  Fevmat's 
  Law. 
  157 
  

  

  24. 
  A 
  further 
  point 
  may 
  be 
  noted. 
  Since 
  the 
  lumini- 
  

   ferous 
  medium 
  is 
  an 
  electromagnetic 
  field, 
  and 
  the 
  properties 
  

   of 
  the 
  former 
  have 
  been 
  partially 
  explained 
  by 
  identifying 
  

   it 
  with 
  an 
  elastic 
  medium, 
  we 
  may 
  take 
  

  

  ( 
  /, 
  g, 
  h) 
  = 
  (u\r, 
  iVy, 
  iv~) 
  (molecular 
  rotations), 
  

  

  KA7)=(f/y,r), 
  

  

  £, 
  7], 
  f 
  being 
  the 
  elastic 
  displacements, 
  and 
  

  

  Moreover, 
  assuming 
  that 
  the 
  aethereal 
  (or 
  optical) 
  medium 
  is 
  

   a 
  fluid 
  medium, 
  we 
  may 
  obviously 
  note 
  the 
  analogies 
  between 
  

   quantities 
  in 
  Hydrodynamics 
  and 
  Electromagnetism, 
  viz., 
  

  

  U, 
  V, 
  W 
  (velocity 
  of 
  flow) 
  to 
  a, 
  /3, 
  <y 
  (magnetic 
  force), 
  

   fl 
  x 
  , 
  fly, 
  fl* 
  (vortex 
  spins) 
  to 
  u, 
  v, 
  w 
  (currents). 
  

  

  Larmor 
  has 
  developed 
  a 
  dynamical 
  theory 
  of 
  the 
  electro- 
  

   magnetic 
  field 
  based 
  on 
  this 
  two-fold 
  concordance. 
  The 
  

   theory 
  presents 
  difficulties, 
  but 
  its 
  most 
  noticeable 
  feature 
  

   from 
  the 
  present 
  point 
  of 
  view 
  is 
  that 
  it 
  leads 
  to 
  the 
  postulate 
  

   of 
  a 
  kinetic 
  origin 
  for 
  the 
  whole 
  of 
  the 
  energy 
  of 
  the 
  field 
  

   (including 
  intrinsic 
  energy) 
  . 
  

  

  25. 
  Now, 
  the 
  main 
  difficulty 
  of 
  the 
  above 
  theory 
  arises 
  

   (as 
  Larmor 
  has 
  pointed 
  out) 
  from 
  the 
  fact 
  that 
  it 
  is 
  " 
  not 
  

   very 
  successful 
  in 
  unravelling 
  the 
  detailed 
  relations 
  of 
  sether 
  

   and 
  matter. 
  Conception 
  of 
  free 
  electrons 
  effectively 
  removes 
  

   this 
  difficulty." 
  But 
  the 
  theory 
  of 
  electrons, 
  as 
  explaining 
  

   the 
  properties 
  of 
  the 
  electromagnetic 
  field, 
  emphatically 
  

   brings 
  into 
  relief 
  the 
  existence 
  of 
  a 
  certain 
  amount 
  of 
  

   intrinsic 
  energy 
  and 
  the 
  kinetic 
  nature 
  of 
  the 
  total 
  energy 
  of 
  

   the 
  system. 
  This, 
  we 
  propose 
  to 
  develop 
  in 
  a 
  future 
  paper. 
  

  

  26. 
  Again, 
  since 
  electrons 
  or 
  negative 
  charges 
  are 
  elec- 
  

   trified 
  singularities 
  in 
  the 
  field, 
  Faraday 
  tubes 
  must 
  be 
  

   conceived 
  to 
  be 
  issuing 
  from 
  these. 
  These 
  tubes 
  on 
  J. 
  J. 
  

   Thomson's 
  theory 
  move, 
  as 
  we 
  have 
  just 
  seen, 
  with 
  the 
  

   velocity 
  of 
  light 
  through 
  the 
  medium. 
  The 
  mode 
  of 
  light 
  

   propagation 
  or 
  its 
  mechanism 
  may, 
  therefore, 
  be 
  thus 
  stated 
  

   in 
  terms 
  of 
  moving 
  Faraday 
  tubes. 
  

  

  27. 
  From 
  a 
  source 
  of 
  electromagnetic 
  energy 
  issue 
  

   " 
  Faraday 
  tubes 
  " 
  which 
  move 
  through 
  the 
  medium 
  at 
  right 
  

   angles 
  to 
  themselves 
  along 
  the 
  line 
  of 
  energy 
  flow 
  (with 
  the 
  

   velocity 
  of 
  light). 
  If 
  the 
  electromagnetic 
  energy 
  suffers 
  

   periodic 
  variation, 
  the 
  number 
  of 
  tubes 
  issuing 
  will 
  also 
  suffer 
  

   periodic 
  variation. 
  

  

  This 
  mode 
  of 
  representation, 
  as 
  J. 
  J. 
  Thomson 
  has 
  remarked, 
  

  

  