﻿638 
  Messrs. 
  E. 
  Bellini 
  and 
  A. 
  Tosi 
  

  

  on 
  a 
  

  

  specimens 
  tested, 
  always 
  below 
  one 
  part 
  in 
  a 
  thousand 
  o£ 
  

   the 
  theoretical 
  equilibrium 
  amount' 
  which 
  should 
  be 
  present 
  

   in 
  the 
  natural 
  mineral. 
  The 
  main 
  part 
  by 
  far 
  of 
  the 
  parent 
  

   of 
  radium 
  in 
  minerals 
  is 
  probably 
  contained 
  in 
  the 
  mother- 
  

   liquors 
  from 
  the 
  crystallization 
  of 
  the 
  uranium 
  salts, 
  and 
  so 
  

   is 
  lost. 
  

  

  (2) 
  In 
  the 
  carefully 
  purified 
  uranium 
  salts 
  prepared 
  by 
  

   Mr. 
  T. 
  D. 
  Mackenzie 
  in 
  1905-06, 
  the 
  growth 
  of 
  radium 
  in 
  

   one 
  case 
  is 
  not 
  greater 
  than 
  5 
  x 
  10~ 
  n 
  gram 
  per 
  kilogram 
  of 
  

   uranium 
  in 
  2f 
  'years, 
  and 
  in 
  the 
  other 
  it 
  is 
  not 
  above 
  10~ 
  n 
  gram 
  

   per 
  kilogram 
  of 
  uranium 
  in 
  1| 
  years. 
  It 
  can 
  be 
  shown 
  from 
  

   these 
  data 
  that 
  if 
  there 
  exists 
  only 
  one 
  long-lived 
  intermediate 
  

   body 
  between 
  uranium 
  and 
  radium, 
  its 
  period 
  of 
  average 
  life 
  

   must 
  not 
  be 
  less 
  than 
  16,500 
  years, 
  or 
  six 
  times 
  that 
  of 
  

   radium 
  ; 
  so 
  that 
  at 
  least 
  six 
  times 
  more 
  of 
  it 
  than 
  of 
  radium 
  

   must 
  exist 
  m 
  minerals. 
  If 
  there 
  be 
  two 
  such 
  bodies, 
  the 
  

   product 
  of 
  their 
  periods 
  must 
  be 
  at 
  least 
  10,000 
  years 
  ; 
  and 
  if 
  

   they 
  are 
  equal 
  each 
  must 
  be 
  not 
  less 
  than 
  100 
  years. 
  

  

  Physical 
  Chemistry 
  Laboratory, 
  

   The 
  University 
  of 
  Glasgow. 
  

   lOAiisr. 
  1908. 
  

  

  LIII. 
  A 
  Directive 
  System 
  of 
  Wireless 
  Telegraphy. 
  

   By 
  E. 
  Bellini 
  and 
  A. 
  Tosi*. 
  

  

  Part 
  I. 
  — 
  Bilateral 
  Directive 
  Wireless 
  Telegraphy 
  using 
  Closed 
  

   'Oscillatory 
  Circuits: 
  (i.) 
  for 
  Transmission 
  ; 
  (ii.) 
  for 
  Reception 
  ; 
  (hi.) 
  for 
  

   both 
  Transmission 
  and 
  Reception. 
  

  

  Part 
  II. 
  — 
  New 
  Unilateral 
  Directive 
  Method 
  : 
  Simultaneous 
  Use 
  of 
  

   'Closed 
  Oscillatory 
  Aerial 
  Circuits 
  and 
  the 
  Open 
  Oscillator 
  or 
  Vertical 
  

   Antenna. 
  

  

  THE 
  authors, 
  having 
  lately 
  obtained 
  some 
  interesting 
  and 
  

   very 
  remarkable 
  results 
  in 
  the 
  course 
  of 
  their 
  work 
  

   upon 
  a 
  further 
  development 
  of 
  their 
  directive 
  system, 
  propose 
  

   to 
  give 
  an 
  account 
  of 
  the 
  arrangements 
  employed 
  and 
  the 
  

   results 
  attained. 
  

  

  Since 
  the 
  complete 
  understanding 
  of 
  these 
  experiments 
  

   depends 
  upon 
  the 
  properties 
  shown 
  by 
  the 
  closed 
  oscillatory 
  

   circuits 
  used 
  by 
  the 
  authors, 
  it 
  is 
  considered 
  desirable, 
  in 
  

   the 
  first 
  part 
  of 
  the 
  paper, 
  to 
  recapitulate, 
  as 
  briefly 
  as 
  

   possible, 
  the 
  main 
  features 
  of 
  the 
  original 
  method, 
  thus 
  

   ^enabling 
  a 
  more 
  comprehensive 
  view 
  to 
  be 
  taken 
  of 
  the 
  later 
  

  

  *' 
  Communicated 
  by 
  the 
  Physical 
  Society 
  : 
  read 
  June 
  12, 
  1908. 
  

  

  