﻿158 
  Improved 
  Form 
  of 
  Magnetometer. 
  

  

  preventing 
  tlie 
  coils 
  of 
  the 
  platinum 
  wire 
  from 
  changing 
  

   their 
  positions 
  when 
  expanded 
  by 
  heat. 
  A 
  cylinder 
  of 
  

   electrolytic 
  sheet-copper 
  is 
  placed 
  within 
  the 
  tube 
  E, 
  and 
  

   assists 
  in 
  maintaining 
  a 
  very 
  uniform 
  temperature 
  over 
  the 
  

   space 
  occupied 
  by 
  the 
  specimens. 
  

  

  In 
  the 
  figure 
  the 
  platinum 
  wire 
  is 
  shown 
  equally 
  spaced 
  

   over 
  the 
  porcelain 
  tube. 
  In 
  reality 
  this 
  is 
  far 
  from 
  being 
  

   the 
  case. 
  The 
  proper 
  winding 
  of 
  the 
  tube 
  is 
  an 
  exceedingly 
  

   troublesome 
  operation, 
  and 
  can 
  only 
  be 
  accomplished 
  by 
  

   repeated 
  trial. 
  

  

  The 
  temperature 
  of 
  the 
  furnace 
  is 
  measured 
  by 
  means 
  of 
  

   the 
  ordinary 
  thcrmo 
  - 
  element 
  or 
  a 
  platinum 
  resistance 
  

   thermometer. 
  The 
  two 
  wooden 
  stands 
  used 
  for 
  the 
  pyro- 
  

   meter 
  are 
  shown 
  in 
  position 
  in 
  figs. 
  4 
  and 
  4 
  A. 
  As 
  will 
  be 
  

   seen 
  at 
  once, 
  the 
  several 
  slots 
  in 
  the 
  horizontal 
  carrier 
  for 
  

   fitting 
  on 
  the 
  tops 
  of 
  the 
  stands 
  permit 
  of 
  these 
  latter 
  being- 
  

   placed 
  clear 
  of 
  the 
  sliding 
  bases 
  of 
  the 
  compensating 
  coils. 
  

  

  Fig. 
  6. 
  

  

  E 
  ^ 
  ft 
  A 
  

  

  i 
  a 
  C 
  " 
  — 
  1^. 
  — 
  I-^ 
  "^ 
  

  

  For 
  tests 
  at 
  the 
  temperature 
  of 
  liquid 
  air 
  the 
  arrangement 
  

   shown 
  in 
  fig. 
  6 
  is 
  employed. 
  The 
  specimen 
  A 
  is 
  enclosed 
  in 
  

   a 
  glass 
  tube 
  BCD, 
  of 
  which 
  the 
  end 
  B 
  is 
  closed 
  and 
  the 
  end 
  

   D 
  is 
  open 
  and 
  bent 
  up. 
  Cork 
  bungs 
  F, 
  F 
  are 
  fitted 
  on 
  the 
  

   tube 
  so 
  as 
  to 
  bring 
  the 
  axis 
  of 
  the 
  specimen 
  into 
  coincidence 
  

   with 
  that 
  of 
  the 
  solenoid. 
  A 
  third 
  bung 
  F 
  or 
  a 
  pad 
  of 
  

   cotton-wool 
  is 
  used 
  to 
  prevent 
  access 
  of 
  warm 
  air 
  into 
  the 
  

   interior 
  of 
  the 
  solenoid, 
  and 
  a 
  covering 
  of 
  cotton-wool 
  on 
  

   the 
  portion 
  CD 
  prevents 
  it 
  from 
  warming 
  up 
  and 
  conducting 
  

   heat 
  to 
  the 
  specimen. 
  Instead 
  of 
  closing 
  the 
  glass 
  tube 
  at 
  B, 
  

   a 
  cork 
  may 
  be 
  used 
  to 
  stop 
  up 
  the 
  opening. 
  The 
  cork, 
  

   however, 
  if 
  dry, 
  is 
  liable 
  to 
  loosen 
  and 
  permit 
  the 
  liquid 
  air 
  

   to 
  leak 
  out, 
  or 
  if 
  it 
  is 
  at 
  all 
  damp 
  it 
  expands 
  and 
  fractures 
  

   the 
  tube. 
  

  

  Where 
  tests 
  have 
  to 
  be 
  made 
  as 
  the 
  specimen 
  slowly 
  

   warms 
  up 
  from 
  the 
  temperature 
  of 
  liquid 
  air, 
  a 
  Dewar 
  tube 
  

   is 
  used, 
  with 
  its 
  mouth 
  closed 
  by 
  a 
  cork 
  which 
  has 
  two 
  bent 
  

   tubes 
  passed 
  through 
  it 
  — 
  one 
  for 
  pouring 
  in 
  the 
  liquid 
  air, 
  

   and 
  the 
  other 
  for 
  the 
  bringing 
  out 
  of 
  the 
  leads 
  from 
  one 
  or 
  

   more 
  thermo-elements 
  in 
  contact 
  with 
  the 
  specimen. 
  

  

  