﻿176 
  

  

  Mr. 
  W. 
  Duddell 
  on 
  a 
  

  

  bronze 
  for 
  the 
  wires. 
  There 
  would 
  be 
  no 
  objection 
  to 
  doing 
  

   this 
  except 
  that 
  the 
  upper 
  limit 
  of 
  the 
  frequency 
  to 
  which 
  the 
  

   instrument 
  could 
  be 
  tuned, 
  without 
  risk 
  of 
  breaking 
  the 
  wires^ 
  

   would 
  be 
  some 
  somewhat 
  reduced. 
  

  

  Fig. 
  9. 
  

  

  lOO 
  200 
  300 
  400 
  

  

  &00 
  

  

  SECOND 
  

  

  7oa 
  

  

  In 
  view 
  of 
  the 
  importance 
  of 
  the 
  fact 
  that 
  the 
  back 
  E.M.F. 
  

   reduces 
  the 
  sensibility 
  of 
  the 
  instrument, 
  I 
  have 
  made 
  some 
  

   tests 
  to 
  determine 
  its 
  value, 
  using 
  the 
  same 
  connexions 
  as 
  

   before 
  :— 
  • 
  

  

  