﻿Radium 
  Emanation 
  in 
  the 
  Atmosphere. 
  603 
  

  

  thought 
  that 
  the 
  good 
  conducting 
  qualities 
  of 
  the 
  metal 
  

   compared 
  with 
  those 
  of 
  glass 
  would 
  more 
  than 
  counter- 
  

   balance 
  the 
  large 
  capacity 
  of 
  heat 
  and 
  the 
  consequent 
  large 
  

   consumption 
  of 
  liquid 
  air. 
  AB 
  (fig. 
  4) 
  is 
  a 
  straight 
  thin 
  

   brass 
  tube 
  about 
  42 
  cms. 
  long 
  and 
  *43 
  cm. 
  in 
  external 
  

   diameter. 
  It 
  fits 
  centrally 
  through 
  a 
  thin 
  tube 
  CD, 
  20 
  cms. 
  

   long 
  and 
  '69 
  cm. 
  in 
  external 
  diameter 
  so 
  that 
  5 
  cms. 
  are 
  

   outside 
  at 
  the 
  higher 
  end 
  and 
  17 
  cms. 
  at 
  the 
  lower 
  end. 
  

   CD 
  supports 
  a 
  much 
  wider 
  brass 
  tube 
  EF 
  17 
  cms. 
  long, 
  

   2*75 
  cms. 
  in 
  external 
  diameter, 
  and 
  2'62 
  cms. 
  in 
  internal 
  

   diameter, 
  r 
  and 
  closed 
  at 
  both 
  ends 
  except 
  where 
  attached 
  

   to 
  CD. 
  The 
  space 
  between 
  AB 
  and 
  EF 
  is 
  packed 
  tightly 
  

   full 
  with 
  straight 
  brass 
  wires 
  16 
  cms. 
  long 
  and 
  *185 
  cm. 
  in 
  

   diameter. 
  154 
  such 
  wires 
  were 
  got 
  into 
  the 
  annular 
  space. 
  

   These 
  wires 
  leave 
  spaces 
  *5 
  cm. 
  deep 
  at 
  the 
  top 
  and 
  bottom 
  

   of 
  EF 
  so 
  that 
  AB 
  can 
  deliver 
  air 
  to 
  the 
  bottom 
  of 
  the 
  

   apparatus; 
  this 
  air 
  can 
  pass 
  up 
  between 
  the 
  wires, 
  collect 
  at 
  

   the 
  top 
  of 
  EF, 
  and 
  pass 
  out 
  along 
  CD 
  and 
  the 
  side 
  tube 
  

   attached 
  to 
  the 
  upper 
  end 
  of 
  CD. 
  

  

  Calculations 
  relating 
  to 
  the 
  Condenser. 
  

  

  It 
  is 
  of 
  interest 
  now 
  to 
  calculate 
  the 
  approximate 
  sum 
  of 
  

   the 
  cross-sections 
  of 
  the 
  tubular 
  spaces 
  thus 
  formed. 
  Fig. 
  5 
  

  

  Fier. 
  5. 
  

  

  represents 
  a 
  number 
  of 
  rods 
  in 
  close 
  contact 
  (I 
  cannot 
  

   conclude 
  that 
  my 
  rods 
  were 
  packed 
  so 
  closely 
  as 
  is 
  here 
  

   shown 
  but 
  no 
  doubt 
  patches 
  of 
  them 
  were). 
  

  

  Let 
  the 
  radius 
  of 
  cross-section 
  of 
  the 
  wires 
  = 
  a 
  cm. 
  

  

  Then 
  area 
  of 
  the 
  triangle 
  ABC 
  formed 
  by 
  joining 
  three 
  

   centres 
  = 
  a 
  2 
  V3 
  sq. 
  cm. 
  

  

  