﻿708 
  Prof. 
  G. 
  N. 
  Lewis 
  : 
  A 
  Revision 
  of 
  the 
  

  

  regardless 
  of 
  the 
  nature 
  of 
  the 
  process 
  which 
  the 
  energy- 
  

   change 
  accompanies*. 
  

  

  Since 
  therefore 
  when 
  a 
  body 
  T 
  loses 
  a 
  given 
  quantity 
  of 
  

   energy 
  it 
  always 
  loses 
  a 
  definite 
  quantity 
  of 
  mass, 
  we 
  might 
  

   assume 
  that 
  if 
  it 
  should 
  lose 
  all 
  its 
  energy 
  it 
  would 
  lose 
  all 
  

   its 
  mass, 
  or, 
  in 
  other 
  words, 
  that 
  the 
  mass 
  of 
  a 
  body 
  is 
  a 
  

   direct 
  measure 
  of 
  its 
  total 
  energy, 
  according 
  to 
  the 
  equation, 
  

  

  m 
  =Y 
  2 
  ^ 
  

  

  We 
  should 
  then 
  regard 
  mass 
  and 
  energy 
  as 
  different 
  names 
  

   and 
  different 
  measures 
  of 
  the 
  same 
  quantity, 
  and 
  say 
  that 
  one 
  

   gram 
  equals 
  9 
  x 
  10 
  20 
  ergs 
  in 
  the 
  same 
  sense 
  that 
  we 
  say 
  one 
  

   metre 
  equals 
  39*37... 
  inches. 
  

  

  Plausible 
  as 
  this 
  view 
  seems, 
  it 
  rests 
  upon 
  an 
  additional 
  

   hypothesis 
  besides 
  the 
  fundamental 
  postulate 
  which 
  we 
  have 
  

   chosen. 
  We 
  shall 
  use 
  therefore, 
  not 
  equation 
  (8) 
  but 
  equation 
  

   (7) 
  as 
  the 
  basis 
  of 
  the 
  following 
  work. 
  

  

  It 
  is 
  to 
  be 
  noted 
  that 
  equation 
  (8) 
  has 
  also 
  been 
  obtained 
  

   by 
  Einstein 
  (he. 
  cit.), 
  who 
  derived 
  it 
  from 
  the 
  general 
  equa- 
  

   tions 
  of 
  the 
  electromagnetic 
  theory, 
  with 
  the 
  aid 
  of 
  the 
  

   so-called 
  principle 
  of 
  relativity. 
  That 
  a 
  different 
  method 
  of 
  

   investigation 
  thus 
  leads 
  to 
  the 
  same 
  simple 
  equation 
  we 
  have 
  

   here 
  deduced, 
  speaks 
  decidedly 
  for 
  the 
  truth 
  of 
  our 
  funda- 
  

   mental 
  postulate!. 
  

  

  Comstock 
  (loc. 
  tit.) 
  from 
  electromagnetic 
  theory 
  alone 
  has 
  

   also 
  concluded 
  that 
  mass 
  is 
  proportional 
  to 
  energy, 
  but 
  his 
  

   equation 
  is 
  

  

  4E 
  

  

  To 
  investigate 
  for 
  the 
  cases 
  studied 
  by 
  Comstock 
  the 
  cause 
  

   or 
  the 
  justification 
  for 
  this 
  appearance 
  in 
  the 
  equation 
  of 
  

   the 
  factor 
  4/3 
  would 
  lead 
  too 
  far 
  into 
  electromagnetic 
  theory, 
  

   from 
  which 
  in 
  the 
  present 
  paper 
  I 
  wish 
  to 
  hold 
  entirely 
  aloof. 
  

   Before 
  proceeding 
  to 
  develop 
  fully 
  the 
  consequences 
  of 
  

   equation 
  (7) 
  it 
  may 
  be 
  well 
  to 
  point 
  out 
  an 
  apparent 
  

  

  * 
  I 
  was 
  first 
  led 
  to 
  an 
  investigation 
  of 
  the 
  relation 
  of 
  mass 
  to 
  energy 
  

   by 
  the 
  work 
  of 
  Landolt, 
  on 
  the 
  change 
  of 
  weight 
  in 
  chemical 
  reactions. 
  

   But 
  it 
  is 
  obvious 
  from 
  equation 
  (7) 
  that 
  although 
  there 
  always 
  will 
  be 
  a 
  

   loss 
  of 
  mass 
  in 
  a 
  reaction 
  which 
  is 
  accompanied 
  by 
  the 
  evolution 
  of 
  energy, 
  

   this 
  loss 
  in 
  the 
  case 
  of 
  any 
  ordinary 
  reaction 
  will 
  be 
  far 
  too 
  small 
  to 
  

   measure. 
  In 
  fact 
  Landolt 
  has 
  very 
  recently 
  shown 
  (Ber. 
  Berlin. 
  Akad. 
  

   1908, 
  p. 
  354) 
  that 
  when 
  all 
  possible 
  precautions 
  are 
  taken 
  there 
  is 
  no 
  

   measurable 
  change 
  of 
  weight 
  in 
  the 
  reactions 
  which 
  he 
  studied. 
  

  

  f 
  Einstein, 
  however, 
  obtains 
  (8) 
  as 
  an 
  approximate 
  formula, 
  while 
  we 
  

   obtain 
  both 
  (7) 
  and 
  (8) 
  as 
  perfectly 
  exact 
  equations. 
  

  

  