﻿Prof. 
  J. 
  J. 
  Thomson 
  on 
  Positive 
  Rajs. 
  657 
  

  

  So 
  far 
  as 
  the 
  commercial 
  services 
  are 
  concerned, 
  the 
  

   possibility 
  of 
  transmitting 
  messages 
  to 
  one 
  station 
  without 
  

   affecting 
  the 
  others, 
  results 
  in 
  the 
  stations 
  having 
  an 
  increased 
  

   working 
  capacity 
  and 
  consequently 
  in 
  an 
  enhancement 
  of 
  their 
  

   commercial 
  value. 
  The 
  ability 
  to 
  receive 
  from 
  one 
  determined 
  

   direction 
  renders 
  the 
  receiving 
  station 
  independent 
  of 
  extrane- 
  

   ous 
  transmissions, 
  and 
  even 
  owing 
  to 
  this 
  circumstance 
  alone 
  

   the 
  working 
  capacity 
  of 
  the 
  stations 
  is 
  raised. 
  Further, 
  the 
  

   ability 
  to 
  determine 
  the 
  origin 
  of 
  a 
  transmission, 
  apart 
  from 
  

   its 
  obvious 
  advantages, 
  presents 
  the 
  advantage 
  of 
  enabling 
  

   the 
  route 
  to 
  be 
  followed 
  by 
  a 
  ship 
  proceeding 
  to 
  the 
  assistance 
  

   of 
  another 
  in 
  danger, 
  to 
  be 
  indicated. 
  

  

  From 
  the 
  strategic 
  point 
  of 
  view 
  the 
  directive 
  reception 
  

   enables 
  one 
  to 
  learn 
  of 
  the 
  presence 
  of 
  the 
  enemy 
  in 
  a 
  certain 
  

   direction 
  and 
  to 
  follow 
  him 
  in 
  his 
  movements. 
  The 
  directive 
  

   transmission 
  will 
  allow, 
  when 
  suitably 
  employed, 
  of 
  trans- 
  

   mitting 
  to 
  one's 
  friends 
  without 
  the 
  enemy 
  being 
  able 
  to 
  

   receive 
  the 
  waves 
  — 
  for 
  the 
  simple 
  reason 
  that 
  there 
  are 
  no 
  

   waves 
  there 
  to 
  be 
  detected 
  in 
  the 
  undesirecl 
  region. 
  

  

  In 
  conclusion, 
  the 
  following 
  is 
  given 
  as 
  one 
  practical 
  

   example 
  of 
  the 
  main 
  strategical 
  advantage 
  of 
  the 
  directive 
  

   system. 
  Supposing 
  it 
  were 
  necessary 
  to 
  send 
  radio-telegraphic 
  

   messages 
  to 
  the 
  cruiser 
  squadrons 
  on 
  the 
  north-east, 
  north, 
  

   north-west, 
  and 
  west 
  coasts 
  of 
  the 
  United 
  Kingdom 
  ; 
  if 
  the 
  

   messages 
  were 
  sent 
  by 
  an 
  ordinary 
  vertical 
  antenna 
  system 
  

   they 
  would 
  be 
  perceived 
  in 
  Denmark, 
  in 
  Germany, 
  in 
  Belgium, 
  

   Holland, 
  and 
  France. 
  Employing, 
  on 
  the 
  other 
  hand, 
  the 
  

   unilateral 
  system, 
  the 
  messages 
  sent 
  from 
  London 
  to 
  the 
  

   Fleet 
  would 
  not 
  be 
  received 
  outside 
  the 
  United 
  Kingdom. 
  

  

  The 
  authors 
  desire 
  to 
  thank 
  Mr. 
  L. 
  H. 
  Walter 
  for 
  trans- 
  

   lating 
  this 
  paper 
  from 
  the 
  original. 
  

  

  LIV. 
  Positive 
  Rays. 
  By 
  J. 
  J. 
  Thomson, 
  M.A., 
  F.R.S. 
  ; 
  

  

  Cavendish 
  Professor 
  of 
  Experimental 
  Physics, 
  Cambridge 
  ; 
  

   Professor 
  of 
  Natural 
  Philosophy 
  at 
  the 
  Royal 
  Institution 
  *. 
  

  

  THOUGH 
  the 
  ordinary 
  cathode 
  rays 
  are 
  the 
  most 
  con- 
  

   spicuous 
  of 
  the 
  rays 
  spreading 
  out 
  from 
  the 
  cathode 
  

   in 
  a 
  vacuum-tube, 
  there 
  are 
  other 
  rays 
  mixed 
  with 
  them, 
  

   which 
  as 
  Goldstein 
  ( 
  Verhandl. 
  d. 
  Deutscli. 
  physik. 
  Gesellsch. 
  

   iv. 
  p. 
  22^, 
  1902) 
  and 
  the 
  writer 
  (Proc. 
  (Jamb. 
  Phil. 
  Soe. 
  ix. 
  

   p. 
  243) 
  showed 
  long 
  ago 
  are 
  not 
  appreciably 
  deflected 
  by 
  

   weak 
  magnetic 
  fields. 
  The 
  very 
  complete 
  study 
  of 
  the 
  region 
  

   near 
  the 
  cathode 
  made 
  by 
  Goldstein, 
  the 
  results 
  of 
  which 
  are 
  

   * 
  Communicated 
  by 
  the 
  Author. 
  

  

  Phii. 
  Mac,. 
  Ser. 
  6, 
  Vol. 
  16. 
  No.'94. 
  Oct. 
  1908. 
  2 
  X 
  

  

  