﻿96 
  

  

  Prof. 
  W. 
  Stroud 
  on 
  a 
  Telemetrlcal 
  

  

  The 
  wire 
  is 
  now 
  replaced 
  by 
  the 
  lens 
  and 
  the 
  operation 
  

   repeated 
  with 
  the 
  R.F., 
  the 
  readings 
  for 
  the 
  one 
  face 
  being 
  

   taken 
  from 
  the 
  one 
  side, 
  the 
  readings 
  for 
  the 
  second 
  face 
  from 
  

   the 
  other. 
  

  

  The 
  differences 
  between 
  the 
  sets 
  of 
  readings 
  for 
  the 
  wire 
  

   and 
  the 
  corresponding 
  sets 
  for 
  the 
  lens 
  gives 
  the 
  thickness 
  

   required. 
  

  

  The 
  principal 
  points, 
  the 
  focal 
  length, 
  and 
  the 
  refractive 
  

   index 
  can 
  now 
  be 
  obtained 
  in 
  the 
  ordinary 
  way. 
  

  

  The 
  following 
  results 
  were 
  obtained 
  for 
  the 
  focal 
  length 
  for 
  

   sodium 
  light, 
  u 
  and 
  v 
  being 
  referred 
  to 
  the 
  principal 
  points. 
  

  

  u. 
  

  

  c. 
  

  

  /. 
  

  

  (*• 
  

  

  2410 
  

   3140 
  

   3213 
  

   35 
  21 
  

  

  1333 
  

   15-31 
  

   15-45 
  

   16-13 
  

  

  29-82 
  

   29-87 
  

   29 
  75 
  

   29-77 
  

  

  1-5276 
  

   1-5268 
  

  

  1-5287 
  

   15284 
  

  

  

  Mean 
  

  

  29-80 
  

  

  1-5279 
  

  

  

  

  The 
  results 
  are 
  remarkably 
  good 
  when 
  it 
  is 
  remembered 
  

   that 
  all 
  the 
  observations 
  are 
  simple 
  naked-eye 
  observations 
  

   without 
  the 
  assistance 
  of 
  any 
  magnify 
  ing-power. 
  

  

  Fiir. 
  3. 
  

  

  L 
  1 
  

  

  V. 
  

  

  Fig. 
  3 
  shows 
  in 
  plan 
  another 
  form 
  which 
  the 
  R.F. 
  may 
  

   take. 
  A, 
  A! 
  are, 
  as 
  before, 
  the 
  prime 
  reflectors. 
  The 
  com- 
  

  

  