﻿the 
  Actinium 
  and 
  Thorium 
  Emanations. 
  123 
  

  

  was 
  proportional 
  to 
  the 
  difference 
  o£ 
  potential. 
  The 
  heatino- 
  

   effect 
  of 
  the 
  circuit 
  through 
  the 
  spiral 
  was 
  found 
  to 
  be 
  

  

  Ek. 
  1. 
  

  

  MILU-VOLTMETER 
  

  

  TO 
  EARTH 
  

  

  TO 
  BAROMETER 
  

  

  

  TO 
  PUMP 
  

  

  J 
  

  

  izr 
  

  

  C 
  z 
  C, 
  

  

  ACTIVE 
  

  

  PREPARATION 
  

  

  5$ 
  

  

  9 
  

  

  : 
  

  

  ?a 
  

  

  | 
  

  

  r 
  

  

  negligible. 
  The 
  thermometer 
  was 
  calibrated 
  from 
  three 
  

   different 
  temperature 
  readings, 
  viz. 
  0° 
  C. 
  ; 
  the 
  freezing- 
  

   point 
  o£ 
  ethyl 
  bromide, 
  — 
  125°*5 
  C; 
  and 
  the 
  temperature 
  

   of 
  liquid 
  air, 
  which 
  had 
  been 
  determined 
  by 
  the 
  aid 
  of 
  a 
  

   hydrogen 
  thermometer 
  just 
  before 
  calibration. 
  Subjoined 
  

   are 
  the 
  results 
  : 
  — 
  

  

  Temperature. 
  Galvanometer 
  reading. 
  

  

  0°C 
  66-6 
  

  

  -125 
  c 
  -5 
  C 
  41-2 
  

  

  -193°-6 
  C 
  24-3 
  

  

  When 
  plotted, 
  these 
  points 
  do 
  not 
  lie 
  on 
  a 
  straight 
  line 
  ; 
  

   but 
  since 
  the 
  deviations 
  therefrom 
  are 
  very 
  small, 
  intermediate 
  

   temperatures 
  can 
  be 
  determined 
  by 
  interpolation. 
  

  

  Now, 
  if 
  the 
  emanation 
  for 
  initial 
  activity 
  I 
  is 
  led 
  into 
  an 
  

   electroscope 
  after 
  being 
  left 
  for 
  T 
  seconds 
  in 
  the 
  spiral, 
  its 
  

   activity 
  will 
  be 
  I 
  e~ 
  AT 
  , 
  if 
  no 
  condensation 
  takes 
  place. 
  And 
  

   the 
  rate 
  of 
  fall 
  of 
  the 
  gold 
  leaf 
  is 
  proportional 
  to 
  I 
  T 
  e 
  - 
  ^; 
  thus 
  

  

  t 
  dt 
  ~^ 
  e 
  ' 
  

  

  where 
  k 
  is 
  a 
  constant, 
  s 
  the 
  reading 
  of 
  the 
  gold-leaf 
  at 
  time 
  t, 
  

  

  