﻿8G8 
  

  

  Mr. 
  B. 
  W. 
  Clack 
  on 
  the 
  

  

  solution 
  at 
  the 
  lower 
  end 
  of 
  the 
  tube 
  D 
  ; 
  while 
  the 
  upper 
  

   end 
  is 
  in 
  contact 
  with 
  such 
  a 
  large 
  volume 
  of 
  water 
  that 
  it 
  

   may 
  be 
  considered 
  to 
  remain 
  practically 
  pure. 
  The 
  con- 
  

   ditions 
  studied 
  in 
  § 
  2 
  thus 
  apply, 
  and 
  as 
  diffusion 
  proceeds 
  

   the 
  weight 
  of 
  the 
  suspended 
  system 
  will 
  decrease. 
  If, 
  then, 
  

   a 
  slightly 
  deBcient 
  weight 
  be 
  placed 
  in 
  the 
  opposite 
  scale- 
  

   pan, 
  the 
  beam 
  will 
  turn 
  until 
  it 
  reaches 
  the 
  supports. 
  As 
  

   time 
  proceeds, 
  however, 
  the 
  weight 
  of 
  the 
  apparatus 
  will 
  

   ultimately 
  become 
  equal 
  to 
  that 
  on 
  the 
  balance-pan, 
  and 
  the 
  

   pointer 
  will 
  move 
  to 
  the 
  zero 
  of 
  its 
  scale. 
  An 
  automatic 
  

   device 
  was 
  designed 
  which 
  would 
  register 
  the 
  exact 
  time 
  at 
  

   which 
  this 
  occurred. 
  A 
  very 
  fine 
  platinum 
  wire 
  P 
  (fig. 
  3) 
  

  

  soldered 
  on 
  to 
  the 
  lower 
  end 
  of 
  the 
  balance-pointer, 
  and 
  

   whm 
  the 
  beam 
  is 
  in 
  equilibrium, 
  P 
  makes 
  contact 
  with 
  a 
  

   fine 
  strip 
  of 
  platinum-foil 
  F, 
  suitably 
  mounted 
  opposite 
  the 
  

   zero 
  of 
  the 
  balance-scale. 
  A 
  delicate 
  phosphor-bronze 
  strip 
  

   Q, 
  such 
  as 
  is 
  employed 
  for 
  galvanometer 
  suspensions, 
  served 
  

   to 
  connect 
  the 
  upper 
  end 
  of 
  the 
  pointer 
  to 
  a 
  battery 
  E, 
  which 
  

   was 
  connected 
  in 
  series 
  with 
  a 
  mercury 
  lever-switch 
  K, 
  and 
  

   an 
  electromagnetic 
  trigger 
  M. 
  

  

  On 
  contact 
  being 
  made 
  between 
  P 
  and 
  F 
  the 
  armature 
  of 
  

   the 
  trigger 
  is 
  attracted, 
  thus 
  allowing 
  a 
  light 
  wooden 
  lath 
  L, 
  

   which 
  is 
  resting 
  upon 
  the 
  trigger, 
  to 
  fall. 
  This 
  lath 
  is 
  

   pivoted 
  at 
  G-, 
  and 
  is 
  provided 
  at 
  this 
  end 
  with 
  a 
  flexible 
  

   copper 
  strip 
  a, 
  which, 
  as 
  the 
  lath 
  falls, 
  is 
  brought 
  into 
  con- 
  

   tact 
  with 
  the 
  balance-wheel 
  of 
  a 
  common 
  alarm-clock, 
  from 
  

   which 
  the 
  back 
  has 
  been 
  removed, 
  and 
  which 
  is 
  suitably 
  

   placed 
  on 
  the 
  table. 
  

  

  The 
  clock 
  is 
  thus 
  stopped 
  at 
  the 
  exact 
  time 
  at 
  which 
  the 
  

   pointer 
  reached 
  the 
  zero 
  of 
  the 
  balance-scale. 
  

  

  In 
  its 
  fall 
  another 
  copper 
  strip 
  h, 
  attached 
  to 
  the 
  lath, 
  

   knocks 
  over 
  the 
  mercury 
  switch 
  K, 
  and 
  thus 
  breaks 
  the 
  

   electric 
  circuit. 
  

  

  