﻿746 
  Mr. 
  W. 
  T. 
  Kennedy 
  on 
  the 
  Active 
  Deposit 
  

  

  In 
  the 
  various 
  experiments 
  referred 
  to 
  above 
  on 
  the 
  active 
  

   deposits 
  from 
  radium, 
  thorium, 
  and 
  actinium, 
  the 
  different 
  

   investigators 
  — 
  with 
  the 
  exception 
  of 
  Debierne 
  — 
  do 
  not 
  appear 
  

   to 
  have 
  taken 
  any 
  precaution 
  to 
  study 
  the 
  behaviour 
  of 
  the 
  

   active 
  deposits 
  with 
  uniform 
  electric 
  fields, 
  and 
  as 
  it 
  was 
  

   thought 
  that 
  some 
  points 
  which 
  are 
  more 
  or 
  less 
  obscure 
  in 
  

   connexion 
  with 
  these 
  active 
  deposits 
  might 
  be 
  cleared 
  up 
  if 
  

   they 
  were 
  studied 
  in 
  this 
  manner, 
  it 
  was 
  decided 
  to 
  apply 
  this 
  

   method 
  to 
  the 
  investigation 
  of 
  the 
  active 
  deposits 
  from 
  

   actinium, 
  which 
  on 
  account 
  of 
  the 
  short 
  life 
  of 
  its 
  emanation 
  

   is 
  peculiarly 
  suitable 
  for 
  the 
  purpose. 
  

  

  II. 
  Apparatus. 
  

  

  The 
  apparatus 
  consisted 
  of 
  a 
  metallic 
  cylinder 
  about 
  5*5 
  cm.. 
  

   in 
  diameter, 
  which 
  was 
  supported 
  horizontally 
  in 
  an 
  air-tight 
  

   chamber. 
  Into 
  this 
  cylinder 
  (as 
  shown 
  in 
  fig. 
  1) 
  there 
  were 
  

  

  IB 
  ATTERY. 
  

  

  Ey^RTH. 
  

  

  fitted 
  two 
  electrodes 
  provided 
  with 
  guard-rings. 
  The 
  salt 
  

   was 
  carried 
  in 
  a 
  small 
  tray 
  which 
  could 
  move 
  freely 
  up 
  and 
  

   down 
  in 
  a 
  vertical 
  tube 
  ^1*5 
  cm. 
  in 
  diameter), 
  which 
  led 
  

   into 
  the 
  cylinder. 
  The 
  tray 
  could 
  be 
  clamped 
  in 
  position 
  at 
  

   any 
  desired 
  distance 
  from 
  the 
  electrodes, 
  and 
  the 
  latter, 
  

   which 
  were 
  capable 
  of 
  easy 
  motion, 
  could 
  readily 
  be 
  placed 
  

   in 
  the 
  exposing 
  cylinder 
  at 
  any 
  selected 
  distance 
  apart. 
  

   The 
  air-tight 
  chamber 
  was 
  also 
  provided 
  with 
  tubes 
  for 
  the 
  

  

  