﻿182 
  Duane 
  and 
  Lory 
  — 
  Electrical 
  Thermostat. 
  

  

  In 
  our 
  apparatus 
  the 
  glass 
  tube 
  e 
  was 
  open 
  at 
  the 
  top. 
  A 
  

   large 
  variation 
  in 
  the 
  atmospheric 
  pressure 
  might 
  produce 
  a 
  

   change 
  in 
  the 
  temperature 
  at 
  which 
  the 
  makes 
  and 
  breaks 
  take 
  

   place 
  on 
  account 
  of 
  the 
  slight 
  compressibility 
  of 
  the 
  alcohol. 
  

   ]STo 
  such 
  effect 
  has 
  been 
  noticed, 
  however. 
  If 
  it 
  occurred 
  the 
  

   fault 
  could 
  easily 
  be 
  remedied 
  by 
  fastening 
  a 
  tube 
  with 
  a 
  large 
  

   bulb 
  on 
  its 
  end 
  to 
  the 
  tube 
  e. 
  The 
  bulb, 
  of 
  course, 
  would 
  

   have 
  to 
  be 
  below 
  the 
  surface 
  of 
  the 
  bath, 
  so 
  that 
  the 
  tempera- 
  

   ture 
  of 
  the 
  air 
  within 
  it 
  would 
  not 
  change. 
  

  

  In 
  practice 
  it 
  is 
  easy 
  to 
  set 
  the 
  regulating 
  device 
  to 
  working 
  

   at 
  any 
  desired 
  temperature 
  between 
  that 
  of 
  the 
  room 
  and 
  one 
  

   a 
  few 
  degrees 
  below 
  the 
  boiling 
  point 
  of 
  the 
  liquid 
  in 
  the 
  tubes, 
  

   as 
  follows. 
  With 
  the 
  cap 
  h 
  unscrewed, 
  allow 
  the 
  bath 
  to 
  heat 
  

   up 
  slowly, 
  and 
  when 
  the 
  desired 
  temperature 
  has 
  nearly 
  been 
  

   reached, 
  screw 
  the 
  cap 
  down. 
  A 
  little 
  practice 
  will 
  enable 
  one 
  

   to 
  set 
  the 
  thermometer 
  at 
  a 
  temperature 
  within 
  a 
  small 
  fraction 
  

   of 
  a 
  degree 
  of 
  the 
  desired 
  one. 
  

  

  The 
  reason 
  that 
  the 
  interruptions 
  of 
  the 
  current 
  follow 
  each 
  

   other 
  so 
  rapidly 
  is 
  not 
  quite 
  clear 
  to 
  us. 
  It 
  may 
  be 
  due 
  to 
  a 
  

   slight 
  jarring 
  of 
  the 
  surface 
  of 
  the 
  mercury 
  at/'. 
  In 
  any 
  case 
  

   the 
  best 
  results 
  are 
  obtained 
  with 
  pure 
  dry 
  mercury, 
  and 
  when 
  

   the 
  platinum 
  wire 
  touches 
  the 
  convex 
  surface 
  of 
  the 
  mercury 
  

   column 
  near 
  its 
  center. 
  

  

  Hale 
  Physical 
  Laboratory, 
  University 
  of 
  Colorado, 
  U. 
  S. 
  A. 
  

  

  