﻿170 
  

  

  Prof. 
  Q. 
  Majorana 
  on 
  the 
  Second 
  

  

  reflected 
  light 
  is 
  variable 
  (and 
  equal 
  to 
  the 
  sum 
  of 
  c 
  = 
  3 
  . 
  10 
  l0 
  cm. 
  

   and 
  the 
  component 
  of 
  the 
  velocity 
  of 
  the 
  image 
  in 
  the 
  direc- 
  

   tion 
  of 
  the 
  ray) 
  we 
  shall 
  have 
  

  

  c 
  r 
  = 
  c 
  + 
  2kv 
  cos 
  0. 
  

  

  And 
  since 
  c' 
  = 
  n 
  f 
  \' 
  and 
  c 
  = 
  n\ 
  we 
  have 
  \' 
  = 
  \. 
  It 
  remains 
  

   ;then 
  to 
  see 
  by 
  experiment 
  whether 
  or 
  not 
  we 
  can 
  observe, 
  

   in 
  addition 
  to 
  the 
  Doppler 
  effect, 
  a 
  variation 
  in 
  the 
  value 
  

   of 
  X; 
  from 
  this 
  we 
  can 
  ascertain 
  whether 
  c 
  remains 
  constant 
  

   or 
  not 
  on 
  reflexion 
  from 
  a 
  moving 
  mirror. 
  I 
  have 
  not 
  pro- 
  

   ceeded 
  to 
  the 
  observation 
  of 
  the 
  Doppler 
  effect 
  in 
  these 
  

   researches 
  since 
  there 
  is 
  no 
  doubt 
  about 
  its 
  existence, 
  already 
  

   proved 
  experimentally 
  by 
  the 
  authors 
  quoted 
  ; 
  I 
  have 
  rather 
  

   sought 
  to 
  find 
  oat 
  whether 
  and 
  in 
  what 
  way 
  X 
  varies 
  when 
  

   the 
  velocity 
  of 
  the 
  moving 
  mirrors 
  changes. 
  

  

  Belopolski's 
  arrangement 
  for 
  the 
  study 
  of 
  the 
  Doppler 
  

   effect 
  was 
  inconvenient 
  on 
  account 
  of 
  the 
  excessive 
  subtility 
  

   of 
  the 
  luminous 
  ray 
  necessary 
  to 
  obtain 
  multiple 
  reflexions 
  

   from 
  the 
  same 
  mirrors 
  ; 
  for 
  this 
  reason 
  the 
  author 
  mentioned 
  

   was 
  unable 
  to 
  observe 
  the 
  displacement 
  of 
  the 
  rays 
  except 
  

   by 
  photography. 
  I 
  prefer 
  to 
  adopt 
  the 
  arrangement 
  shown 
  

   diagrammatically 
  in 
  fig. 
  2. 
  A 
  horizontal 
  brass 
  wheel 
  R, 
  35 
  cm. 
  

  

  Fig. 
  2. 
  

  

  ^ 
  

  

  $ 
  

  

  i 
  

  

  in 
  diameter 
  (6 
  mm. 
  thick), 
  which 
  can 
  be 
  made 
  to 
  revolve 
  

   with 
  a 
  maximum 
  velocity 
  of 
  80 
  turns 
  per 
  second, 
  bears 
  on 
  its 
  

   periphery 
  ten 
  mirrors 
  similar 
  to 
  M, 
  rectangular, 
  plane, 
  

   vertical, 
  of 
  glass 
  silvered 
  at 
  the 
  back. 
  The 
  velocity 
  of 
  the 
  

   centres 
  of 
  the 
  mirrors, 
  corresponding 
  to 
  the 
  greatest 
  velocity 
  

   of 
  rotation, 
  amounts 
  therefore 
  to 
  more 
  than 
  100 
  metres 
  per 
  

  

  