﻿of 
  Atoms 
  and 
  Molecules. 
  15 
  

  

  While 
  there 
  obviously 
  can 
  be 
  no 
  question 
  oE 
  a 
  mechanical 
  

   foundation 
  of 
  the 
  calculations 
  given 
  in 
  this 
  paper, 
  it 
  is, 
  how- 
  

   ever, 
  possible 
  to 
  give 
  a 
  very 
  simple 
  interpretation 
  of: 
  the 
  result 
  

   of 
  the 
  calculation 
  on 
  p. 
  5 
  by 
  help 
  of 
  symbols 
  taken 
  from 
  the 
  

   ordinary 
  mechanics. 
  Denoting 
  the 
  angular 
  momentum 
  of 
  

   the 
  electron 
  round 
  the 
  nucleus 
  by 
  M, 
  we 
  have 
  immediately 
  

  

  T 
  

  

  for 
  a 
  circular 
  orbit 
  7rM=-, 
  where 
  co 
  is 
  the 
  frequency 
  of 
  

  

  revolution 
  and 
  T 
  the 
  kinetic 
  energy 
  of 
  the 
  electron; 
  for 
  a 
  

   circular 
  orbit 
  we 
  further 
  have 
  T= 
  W" 
  (see 
  p. 
  3) 
  aud 
  from 
  (2), 
  

   p. 
  5, 
  we 
  consequently 
  get 
  

  

  M 
  = 
  rM 
  , 
  

   where 
  M 
  =^= 
  1-04x10^. 
  

  

  If 
  we 
  therefore 
  assume 
  that 
  the 
  orbit 
  of 
  the 
  electron 
  in 
  

   the 
  stationary 
  states 
  is 
  circular, 
  the 
  result 
  of 
  the 
  calculation 
  

   on 
  p. 
  5 
  can 
  be 
  expressed 
  by 
  the 
  simple 
  condition 
  : 
  that 
  the 
  

   angular 
  momentum 
  of 
  the 
  electron 
  round 
  the 
  nucleus 
  in 
  a 
  

   stationary 
  state 
  of 
  the 
  system 
  is 
  equal 
  to 
  an 
  entire 
  multiple 
  

   of 
  a 
  universal 
  value, 
  independent 
  of 
  the 
  charge 
  on 
  the 
  

   nucleus. 
  The 
  possible 
  importance 
  of 
  the 
  angular 
  momentum 
  

   in 
  the 
  discussion 
  of 
  atomic 
  systems 
  in 
  relation 
  to 
  Planck's 
  

   theory 
  is 
  emphasized 
  by 
  Nicholson 
  *. 
  • 
  

  

  The 
  great 
  number 
  of 
  different 
  stationary 
  states 
  we 
  do 
  not 
  

   observe 
  except 
  by 
  investigation 
  of 
  the 
  emission 
  and 
  absorption 
  

   of 
  radiation. 
  In 
  most 
  of 
  the 
  other 
  physical 
  phenomena, 
  

   however, 
  we 
  only 
  observe 
  the 
  atoms 
  of 
  the 
  matter 
  in 
  a 
  single 
  

   distinct 
  state, 
  i. 
  e. 
  the 
  state 
  of 
  the 
  atoms 
  at 
  low 
  temperature. 
  

   From 
  the 
  preceding 
  considerations 
  we 
  are 
  immediately 
  led 
  

   to 
  the 
  assumption 
  that 
  the 
  " 
  permanent 
  " 
  state 
  is 
  the 
  one 
  

   among 
  the 
  stationary 
  states 
  during 
  the 
  formation 
  of 
  which 
  

   the 
  greatest 
  a 
  mount 
  of 
  energy 
  is 
  emitted. 
  According 
  to 
  the 
  

   equation 
  (3) 
  on 
  p. 
  5, 
  this 
  state 
  is 
  the 
  one 
  which 
  corresponds 
  

  

  to 
  T=l. 
  

  

  § 
  4. 
  Absorption 
  of 
  Radiation. 
  

  

  In 
  order 
  to 
  account 
  for 
  Kirchhoff's 
  law 
  it 
  is 
  necessary 
  to 
  

   introduce 
  assumptions 
  on 
  the 
  mechanism 
  of 
  absorption 
  of 
  

   radiation 
  which 
  correspond 
  to 
  those 
  we 
  have 
  used 
  considering 
  

   the 
  emission. 
  Thus 
  we 
  must 
  assume 
  that 
  a 
  system 
  consisting 
  

   of 
  a 
  nucleus 
  and 
  an 
  electron 
  rotating 
  round 
  it 
  under 
  certain 
  

   circumstances 
  can 
  absorb 
  a 
  radiation 
  of 
  a 
  frequency 
  equal 
  to 
  

   the 
  frequency 
  of 
  the 
  homogeneous 
  radiation 
  emitted 
  during 
  

  

  * 
  J. 
  W. 
  Nicholson, 
  he. 
  cit. 
  p. 
  679. 
  

  

  