﻿High 
  Temperatures. 
  193 
  

  

  the 
  errors 
  of 
  observation 
  ; 
  even 
  in 
  the 
  vicinity 
  of 
  1000° 
  it 
  is 
  not 
  

   higher 
  than 
  the 
  possible 
  error 
  in 
  the 
  vahie 
  assumed 
  for 
  the 
  coeffi- 
  

   cient 
  of 
  expansion 
  of 
  the 
  bulb 
  (8,9). 
  An 
  increase 
  of 
  10 
  per 
  cent 
  

   in 
  3/S 
  causes 
  an 
  increase 
  of 
  1'5° 
  at 
  1000° 
  for 
  the 
  porcelain 
  scale 
  

   and 
  3'2° 
  for 
  the 
  platinum. 
  Above 
  1000° 
  the 
  values 
  of 
  A 
  in- 
  

   crease 
  rapidly. 
  The 
  values 
  obtained 
  from 
  the 
  platinum 
  bulb 
  

   must 
  be 
  accorded 
  the 
  preference, 
  however, 
  not 
  only 
  on 
  account 
  

   of 
  the 
  constancy 
  of 
  ice 
  point 
  and 
  coefficient 
  of 
  expansion 
  but 
  

   on 
  account 
  of 
  the 
  much 
  reduced 
  error 
  due 
  to 
  the 
  unheated 
  

   space. 
  

  

  It 
  is 
  not 
  impossible 
  that 
  at 
  high 
  temperatures 
  a 
  vapor 
  is 
  

   developed 
  in 
  the 
  porcelain 
  bulbs, 
  in 
  fact 
  in 
  the 
  bulbs 
  contain- 
  

   ing 
  glazing 
  this 
  could 
  quite 
  naturally 
  take 
  place. 
  

  

  Our 
  purpose 
  is 
  to 
  continue 
  the 
  observations 
  with 
  the 
  platin- 
  

   iridium 
  bulb 
  to 
  still 
  higher 
  temperatures 
  and 
  to 
  investigate 
  a 
  

   second 
  similar 
  bulb 
  which 
  the 
  firm 
  of 
  fleraus 
  has 
  kindly 
  

   placed 
  at 
  our 
  disposal. 
  The 
  coefficient 
  of 
  expansion 
  (3/5) 
  and 
  

   the 
  effect 
  of 
  pressure 
  at 
  the 
  higher 
  temperatures 
  will 
  also 
  be 
  

   determined. 
  

  

  Dr. 
  Hans 
  TJsener, 
  who 
  undertook 
  this 
  investigation 
  with 
  us 
  

   and 
  carried 
  on 
  for 
  a 
  considerable 
  time 
  the 
  thermo-electrical 
  

   observations, 
  left 
  it 
  to 
  accept 
  a 
  position 
  at 
  the 
  German 
  Govern- 
  

   ment 
  Torpedo 
  Station 
  at 
  Kiel. 
  

  

  Charlottenburg, 
  June, 
  1899. 
  

  

  