﻿744 
  

  

  Prof. 
  0. 
  W. 
  Richardson 
  on 
  the 
  Specific 
  

  

  The 
  " 
  upper 
  " 
  plane 
  consisted 
  o£ 
  two 
  brass 
  plates 
  ff, 
  shown 
  

   in 
  plan 
  in 
  the 
  top 
  right-hand 
  figure. 
  The 
  ends 
  of 
  these 
  

   were 
  slotted 
  into 
  ebonite 
  pieces 
  ft, 
  which 
  were 
  screwed 
  on 
  to 
  

   the 
  main 
  tebonite 
  frame 
  at 
  bb. 
  The 
  line 
  bab 
  in 
  the 
  central 
  

  

  Fig-. 
  i, 
  

  

  Natural 
  size 
  . 
  

  

  figure 
  thus 
  represents 
  the 
  section 
  of 
  the 
  " 
  upper 
  " 
  plane 
  by 
  

   the 
  plane 
  of 
  the 
  paper. 
  The 
  two 
  plates 
  ff 
  were 
  separated 
  by 
  

   a 
  longitudinal 
  slit 
  somewhat 
  exaggerated 
  in 
  the 
  figure, 
  and 
  

   in 
  addition 
  were 
  cut 
  away 
  at 
  the 
  centre 
  so 
  as 
  to 
  leave 
  a 
  

   narrow 
  rectangular 
  aperture. 
  The 
  platinum 
  strip 
  a, 
  which 
  

  

  