﻿Minute 
  Metal 
  Particles 
  for 
  Light-ivaves 
  . 
  409 
  

  

  over 
  the 
  film. 
  With 
  a 
  sensitive 
  galvanometer 
  in 
  circuit 
  

   with 
  the 
  bulb, 
  75 
  volts 
  gave 
  no 
  deflexion 
  when 
  the 
  wires 
  were 
  

   drawn 
  over 
  the 
  film, 
  though 
  they 
  scraped 
  the 
  glass 
  clean 
  of 
  

  

  the 
  deposit. 
  No 
  change 
  was 
  produced 
  in 
  the 
  appearance 
  of 
  

   the 
  film 
  between 
  the 
  wires 
  with 
  a 
  potential-difference 
  of 
  700 
  

   volts 
  obtained 
  from 
  a 
  storage-battery- 
  With 
  higher 
  voltages 
  

   a 
  gas-discharge 
  commenced, 
  and 
  the 
  colour 
  changed 
  in 
  the 
  

   neighbourhood 
  of 
  the 
  electrodes, 
  owing 
  to 
  the 
  heat. 
  I 
  have 
  

   tried 
  the 
  effect 
  of 
  illuminating 
  the 
  films 
  with 
  the 
  light 
  of 
  an 
  

   arc 
  brought 
  close 
  up 
  to 
  the 
  bulb, 
  but 
  there 
  is 
  absolutely 
  no 
  

   trace 
  of 
  conductivity, 
  even 
  under 
  these 
  conditions. 
  This 
  is 
  

   true 
  even 
  for 
  deposits 
  so 
  dense, 
  that 
  under 
  the 
  microscope 
  

   the 
  particles 
  appear 
  to 
  be 
  in 
  contact 
  with, 
  and 
  even 
  piled 
  up 
  

   on 
  top 
  of 
  one 
  another. 
  A 
  possible 
  explanation 
  of 
  the 
  absence 
  

   of 
  conductivity 
  may 
  be, 
  that 
  the 
  granules 
  consist 
  of 
  a 
  metal 
  

   core, 
  surrounded 
  by 
  a 
  non-conducting 
  film 
  of 
  some 
  sort, 
  

   possibly 
  oxide. 
  I 
  have 
  noticed 
  that 
  bulbs, 
  in 
  which 
  films 
  

   have 
  been 
  repeatedly 
  formed 
  and 
  driven 
  off 
  by 
  the 
  appli- 
  

   cation 
  of 
  a 
  flame, 
  finally 
  reach 
  a 
  state 
  in 
  which 
  it 
  is 
  no 
  longer 
  

   possible 
  to 
  form 
  coloured 
  deposits, 
  but 
  I 
  have 
  not 
  yet 
  deter- 
  

   mined 
  whether 
  this 
  is 
  due 
  to 
  a 
  modification 
  of 
  the 
  surface 
  of 
  

   the 
  glass, 
  the 
  removal 
  of 
  the 
  oxygen, 
  or 
  some 
  other 
  'cause. 
  

   At 
  the 
  present 
  time, 
  I 
  am 
  studying 
  the 
  effects 
  of 
  the 
  intro- 
  

   duction 
  of 
  a 
  small 
  amount 
  of 
  liquid 
  ligroin, 
  which 
  can 
  be 
  

   accomplished 
  without 
  impairing 
  the 
  vacuum, 
  or 
  destroying 
  

   the 
  coloured 
  film, 
  in 
  the 
  following 
  way: 
  — 
  One 
  end 
  of 
  the 
  

   bulb 
  is 
  drawn 
  out 
  into 
  a 
  thin-walled 
  tube 
  with 
  a 
  bore 
  of 
  

   about 
  1 
  mm. 
  After 
  a 
  satisfactory 
  coloured 
  film 
  has 
  been 
  

   formed, 
  a 
  swinging 
  motion 
  of 
  the 
  arm 
  drives 
  the 
  drop 
  of 
  

   molten 
  metal 
  down 
  into 
  the 
  small 
  tube, 
  sealing 
  it 
  hermeti- 
  

   cally. 
  The 
  tip 
  of 
  the 
  tube 
  is 
  then 
  cut 
  off 
  under 
  ligroin, 
  

   which 
  completely 
  fills 
  the 
  tube, 
  as 
  far 
  up 
  as 
  the 
  plug. 
  By 
  

   means 
  of 
  a 
  small 
  flame, 
  it 
  is 
  possible 
  to 
  close 
  the 
  mouth 
  of 
  

   the 
  tube, 
  the 
  empty 
  portion 
  containing 
  practically 
  nothing 
  

   but 
  hydrocarbon 
  vapour. 
  On 
  carefully 
  warming 
  the 
  metal 
  

   plug 
  to 
  the 
  fusing-point, 
  the 
  hydrocarbon 
  is 
  discharged 
  into 
  

   the 
  bulb, 
  passing 
  through 
  the 
  shell 
  of 
  liquid 
  metal 
  which 
  

   adheres 
  to 
  the 
  walls 
  of 
  the 
  tube 
  and 
  removes 
  from 
  the 
  

   Phil 
  Mag. 
  S. 
  6. 
  Vol. 
  3. 
  No. 
  16. 
  April 
  1902. 
  2 
  E 
  

  

  