﻿176 
  HolhoTn 
  and 
  Day 
  — 
  Gas 
  Thermometer 
  at 
  

  

  Inasmuch 
  as 
  the 
  bulbs 
  prepared 
  in 
  this 
  way 
  are 
  often 
  not 
  

   air-tight, 
  we 
  have 
  preferred 
  to 
  take 
  the 
  completely 
  moulded 
  

   though 
  not 
  burned 
  bulb 
  lacking 
  only 
  the 
  end 
  piece 
  E 
  (fig. 
  2), 
  

   cover 
  the 
  inside 
  with 
  glazing 
  solution, 
  set 
  the 
  similarly 
  smeared 
  

   end 
  piece 
  on 
  and 
  burn 
  the 
  whole 
  at 
  once. 
  

  

  This 
  gives 
  of 
  course 
  on 
  the 
  inside 
  an 
  unglazed 
  ridge 
  some 
  

   2""™ 
  wide 
  and 
  the 
  same 
  high 
  where 
  the 
  cap 
  is 
  set 
  on, 
  but 
  this 
  

   has 
  given 
  no 
  trouble. 
  

  

  To 
  obtain 
  a 
  perfectly 
  glazed 
  outside 
  surface 
  (very 
  essential) 
  

   the 
  bulbs 
  must 
  be 
  hung 
  up 
  for 
  burning 
  by 
  the 
  stem, 
  free 
  from 
  

   contact 
  with 
  each 
  other 
  or 
  surrounding 
  bodies. 
  If 
  it 
  is 
  

   desirable 
  that 
  the 
  stem 
  be 
  curved 
  for 
  dipping 
  in 
  a 
  bath, 
  the 
  

   finished 
  stem 
  may 
  readily 
  be 
  bent 
  in 
  the 
  oxy-hydrogen 
  flame 
  

   according 
  to 
  requirements. 
  

  

  The 
  bulbs 
  used 
  by 
  us 
  were 
  made 
  in 
  the 
  " 
  Konigliche 
  Por- 
  

   cellan-Manufactur 
  " 
  Berlin 
  and 
  have 
  the 
  form 
  given 
  in 
  fig. 
  2. 
  

  

  The 
  length 
  was 
  about 
  12"'^, 
  diameter 
  3-7"'°, 
  thickness 
  of 
  the 
  

   walls 
  2°^"^ 
  and 
  the 
  volume 
  approximately 
  100^" 
  '^'". 
  

  

  The 
  length 
  of 
  the 
  capillary 
  stem 
  was 
  regulated 
  according 
  to 
  

   our 
  necessities, 
  the 
  original 
  length 
  being 
  60'="' 
  and 
  the 
  diameter 
  

   inside 
  0'85°'™. 
  At 
  the 
  open 
  end, 
  it 
  was 
  bored 
  out 
  to 
  a 
  

   diameter 
  of 
  2™™ 
  to 
  admit 
  the 
  end 
  of 
  the 
  platinum 
  capillary 
  

   leading 
  to 
  the 
  manometer 
  ; 
  the 
  joint 
  was 
  then 
  made 
  air-tight 
  

   with 
  sealing 
  wax. 
  

  

  As 
  coefficient 
  of 
  expansion 
  the 
  value 
  obtained 
  by 
  Holborn 
  

   and 
  Wien 
  for 
  Berlin 
  porcelain 
  is 
  adopted. 
  

  

  The 
  '' 
  unheated 
  space 
  '' 
  with 
  bulb 
  No. 
  II, 
  mounted 
  as 
  here 
  

   described, 
  was 
  2-837"'=°^. 
  Effect 
  on 
  resulting 
  t 
  at 
  500°, 
  7-5 
  

   per 
  cent; 
  at 
  900°, 
  11*3 
  per 
  cent. 
  

  

  Bitre 
  Bath. 
  — 
  For 
  a 
  while 
  the 
  heating 
  arrangements 
  were 
  

   retained 
  as 
  before, 
  but 
  above 
  500° 
  the 
  nitre 
  bath 
  decomposed 
  more 
  

   rapidly, 
  in 
  consequence 
  of 
  which 
  it 
  became 
  strongly 
  alkaline 
  

   and 
  its 
  melting 
  point 
  sank 
  ; 
  the 
  outside 
  glazing 
  of 
  the 
  bulb 
  

   was 
  also 
  considerably 
  affected 
  but 
  remained 
  air-tight 
  through- 
  

   out 
  the 
  observations. 
  

  

  The 
  highest 
  temperature 
  attainable 
  under 
  these 
  conditions 
  

   is 
  about 
  750°, 
  but 
  the 
  mechanical 
  arrangement 
  for 
  stirring 
  

   could 
  not 
  be 
  used 
  above 
  600°. 
  With 
  an 
  especially 
  powerful 
  

   heater 
  and 
  a 
  smaller 
  bath 
  an 
  attempt 
  was 
  made 
  to 
  carry 
  obser- 
  

  

  