﻿880 
  Mr. 
  E. 
  Parr 
  Metcalfe 
  on 
  

  

  silica 
  tube. 
  The 
  upper 
  end 
  of 
  the 
  silica 
  tube 
  was 
  blown 
  out 
  

   into 
  a 
  cup-shaped 
  opening 
  into 
  which 
  a 
  small 
  iron 
  bung 
  was 
  

   ground 
  to 
  fit. 
  These 
  three 
  joints 
  were 
  made 
  tight 
  with 
  

   marine 
  glue, 
  and 
  that 
  between 
  the 
  glass 
  and 
  iron 
  tubes 
  im- 
  

   mersed 
  in 
  mercury. 
  Into 
  the 
  iron 
  bung 
  was 
  screwed 
  and 
  

   soldered 
  a 
  thin 
  steel 
  rod 
  which 
  passed 
  down 
  the 
  silica 
  tube 
  

   into 
  the 
  chamber, 
  and 
  supported 
  a 
  cylindrical 
  electrode 
  made 
  

   of 
  thin 
  steel 
  tubing 
  2*5 
  cms. 
  in 
  diameter 
  and 
  9 
  cms. 
  long 
  

   (see 
  fig. 
  1, 
  p. 
  869). 
  

  

  Both 
  the 
  inner 
  surface 
  of 
  the 
  chamber 
  and 
  the 
  outer 
  surface 
  

   of 
  the 
  electrode 
  were 
  coated 
  with 
  a 
  very 
  thin 
  layer 
  of 
  uranium 
  

   nitrate 
  by 
  spraying 
  them 
  while 
  warm 
  with 
  a 
  solution 
  of 
  the 
  

   salt. 
  A 
  uniform 
  coating 
  having 
  been 
  deposited 
  in 
  this 
  way, 
  

   the 
  temperature 
  was 
  raised 
  to 
  a 
  red 
  heat 
  so 
  as 
  to 
  drive 
  off 
  

   oxides 
  of 
  nitrogen. 
  In 
  this 
  way 
  a 
  very 
  thin 
  and 
  adherent 
  

   layer 
  of 
  uranium 
  oxide 
  was 
  formed 
  on 
  the 
  curved 
  surfaces 
  of 
  

   chamber 
  and 
  electrode. 
  

  

  This 
  manner 
  of 
  supporting 
  the 
  radiating 
  material 
  possesses 
  

   the 
  advantage 
  of 
  subjecting 
  the 
  gas 
  to 
  bombardment 
  from 
  a 
  

   large 
  active 
  surface, 
  while 
  the 
  thinness 
  of 
  the 
  coating 
  tends 
  

   to 
  diminish 
  the 
  relative 
  importance 
  of 
  the 
  more 
  penetrating 
  

   /5-radiation. 
  

  

  No 
  attempt 
  was 
  made 
  to 
  separate 
  the 
  effects 
  due 
  to 
  the 
  a- 
  

   and 
  /3-radiation 
  respectively. 
  The 
  amount 
  of 
  ionization 
  due 
  to 
  

   ^-radiation 
  is 
  relatively 
  very 
  small 
  ; 
  and 
  moreover 
  it 
  appears 
  

   from 
  the 
  experiments 
  of 
  R. 
  Kleeman 
  that 
  the 
  relative 
  

   /S-ionization 
  in 
  a 
  gas 
  is 
  usually 
  not 
  very 
  different 
  from 
  

   the 
  relative 
  a-ionization 
  under 
  the 
  same 
  conditions 
  in 
  the 
  

   same 
  gas. 
  

  

  The 
  silica 
  insulation 
  proved 
  very 
  effective 
  ; 
  but 
  to 
  reduce 
  

   the 
  chance 
  of 
  electric 
  leakage 
  to 
  the 
  electrode 
  through 
  

   its 
  supports, 
  bands 
  of 
  silver 
  were 
  deposited 
  chemically 
  

   on 
  the 
  glass 
  tube, 
  both 
  inside 
  and 
  outside, 
  and 
  these 
  were 
  

   earthed. 
  

  

  The 
  ionization-chamber 
  was 
  insulated 
  on 
  three 
  ebonite 
  

   blocks, 
  and 
  was 
  connected 
  to 
  the 
  positive 
  pole 
  of 
  a 
  battery 
  

   of 
  secondary 
  cells, 
  the 
  other 
  pole 
  of 
  the 
  battery 
  being 
  earthed. 
  

   Except 
  where 
  otherwise 
  stated, 
  the 
  voltage 
  used 
  was 
  200. 
  

   The 
  electrode 
  in 
  the 
  chamber 
  was 
  connected 
  to 
  an 
  earthing- 
  

   key 
  and 
  to 
  one 
  pair 
  of 
  quadrants 
  of 
  a 
  Dolezalek 
  electro- 
  

   meter 
  ; 
  the 
  other 
  pair 
  of 
  quadrants 
  was 
  earthed. 
  As 
  usual 
  

   the 
  leads 
  from 
  chamber 
  to 
  electrometer^ 
  as 
  well 
  as 
  the 
  

   earthing-key, 
  were 
  enclosed 
  in 
  earthed 
  metal 
  sheaths. 
  The 
  

   electrometer-needle 
  was 
  connected 
  to 
  the 
  200 
  volt 
  terminal 
  

   of 
  the 
  battery. 
  A 
  low 
  sensitiveness 
  of 
  the 
  electrometer 
  was 
  

  

  