﻿26 
  

  

  Prof. 
  Chattock 
  and 
  Mr. 
  Tyndall 
  on 
  Changes 
  

  

  time 
  brought 
  to 
  affect 
  both 
  ends 
  of 
  the 
  gauge, 
  and 
  so 
  became 
  

   inoperative 
  on 
  the 
  latter 
  long 
  before 
  the 
  rise 
  of 
  temperature 
  

   it 
  produced 
  had 
  vanished. 
  

  

  It 
  was 
  found 
  that 
  with 
  the 
  currents 
  used 
  (up 
  to 
  about 
  2'2 
  

   micro-amps.) 
  the 
  heating 
  effects 
  as 
  indicated 
  by 
  the 
  gauge 
  

   were 
  practically 
  over 
  in 
  3 
  or 
  4 
  minutes 
  after 
  stopping 
  the 
  

   discharge, 
  for 
  distances 
  of 
  about 
  2 
  cm. 
  between 
  point 
  and 
  

   plate. 
  For 
  shorter 
  distances 
  the 
  time 
  was 
  also 
  shorter 
  

   of 
  course. 
  The 
  currents 
  were 
  obtained 
  from 
  a 
  Wimshurst, 
  

   and 
  were 
  measured 
  by 
  a 
  galvanometer 
  between 
  A 
  and 
  the 
  

   earthed 
  terminal 
  of 
  the 
  machine. 
  

  

  Gauge 
  and 
  discharge 
  vessels 
  were 
  shielded 
  from 
  external 
  

   heat 
  effects 
  by 
  two 
  cardboard 
  cases, 
  one 
  outside 
  the 
  other, 
  

   double-walled, 
  and 
  filled 
  with 
  sawdust 
  and 
  wool 
  — 
  their 
  joint 
  

   thickness 
  being 
  about 
  9 
  inches. 
  

  

  The 
  gauge 
  contained 
  water. 
  To 
  prevent 
  water-vapour 
  

   from 
  reaching 
  the 
  discharge 
  vessels 
  each 
  limb 
  of 
  the 
  gauge 
  

  

  Curves 
  I. 
  

  

  1^ 
  

  

  ri 
  me 
  

  

  was 
  trapped 
  with 
  mercury. 
  It 
  was 
  found, 
  however, 
  that 
  

   water 
  slowly 
  worked 
  its 
  way 
  pasi 
  this 
  mercury 
  — 
  probably 
  by 
  

   creeping 
  between 
  it 
  and 
  the 
  glass 
  — 
  and 
  small 
  tubes 
  of 
  phos- 
  

   phorus 
  pentoxide 
  were 
  therefore 
  introduced 
  between 
  the 
  

   gauge 
  and 
  the 
  discharge 
  vessels. 
  These 
  tubes 
  were 
  also 
  

  

  