﻿288 
  Messrs. 
  Spiers, 
  Twyman, 
  and 
  Waters 
  on 
  Variations 
  in 
  

  

  the 
  air-bath 
  constant 
  to 
  0°*01 
  C, 
  the 
  gas 
  being 
  cut 
  off 
  and 
  

   coming 
  on 
  again 
  about 
  every 
  five 
  minutes. 
  

  

  To 
  investigate 
  the 
  effect 
  of 
  temperature 
  on 
  the 
  cells, 
  it 
  was 
  

   necessary 
  to 
  be 
  able 
  to 
  vary 
  their 
  temperature 
  so 
  as 
  to 
  get 
  a 
  

   uniform 
  rise 
  or 
  fall. 
  To 
  effect 
  this, 
  some 
  special 
  form 
  of 
  

   heating-bath 
  was 
  needed. 
  In 
  its 
  final 
  form, 
  this 
  heating- 
  

   bath 
  consisted 
  of 
  an 
  outer 
  zinc 
  bath, 
  in 
  which 
  the 
  vessel 
  

   containing 
  the 
  Clark 
  cells 
  was 
  placed, 
  which 
  was 
  divided 
  up 
  

   by 
  means 
  of 
  a 
  number 
  of 
  partitions, 
  reaching 
  from 
  the 
  

   bottom 
  of 
  the 
  vessel 
  to 
  above 
  the 
  surface 
  of 
  the 
  oil. 
  The 
  

   oil 
  was 
  forced 
  alternately 
  under 
  one 
  partition 
  and 
  over 
  the 
  

   next 
  round 
  the 
  whole 
  of 
  the 
  bath, 
  and 
  from 
  the 
  last 
  com- 
  

   partment 
  was 
  drawn 
  off 
  into 
  a 
  separate 
  chamber 
  containing 
  

   a 
  heating-coil 
  and 
  a 
  coil 
  of 
  lead 
  tubing 
  for 
  an 
  iced- 
  water 
  

  

  Fig. 
  2. 
  

  

  SECTION 
  . 
  

  

  SECTION 
  AT 
  OO 
  

  

  PLAN. 
  

  

  circulation, 
  and 
  from 
  this 
  chamber 
  it 
  was 
  again 
  circulate 
  

  

  round 
  the 
  compartments 
  by 
  means 
  of 
  a 
  set 
  of 
  centrifugal 
  vane 
  

  

  A 
  (fig. 
  2) 
  is 
  the 
  outer 
  zinc 
  bath, 
  containing 
  the 
  oil, 
  and 
  divide 
  

  

  