﻿138 
  Uhler 
  and 
  Patterson 
  — 
  Arc 
  Spectrum 
  of 
  Tellurium. 
  

  

  would 
  probably 
  not' 
  suffice 
  to 
  separate 
  the 
  antimony 
  line 
  from 
  

   line 
  2, 
  the 
  interval 
  being 
  about 
  0*29A. 
  [X 
  3175*044 
  is 
  accord- 
  

   ing 
  to 
  our 
  measurements 
  whereas 
  X 
  2769*939 
  is 
  quoted 
  from 
  

   volume 
  VI, 
  page 
  440, 
  of 
  Kayser's 
  " 
  Handbuch." 
  It 
  was 
  

   measured 
  by 
  Schippers.] 
  

  

  In 
  the 
  later 
  work 
  we 
  were 
  given 
  such 
  large 
  quantities 
  of 
  

   especially 
  purified 
  metallic 
  tellurium 
  by 
  Professor 
  Browning 
  

   as 
  to 
  enable 
  us 
  to 
  dispense 
  with 
  the 
  enclosed-arc 
  apparatus 
  and 
  

   to 
  work 
  in 
  air 
  in 
  the 
  usual 
  manner. 
  Between 
  45 
  and 
  110 
  

   volts 
  D. 
  C. 
  it 
  was 
  not 
  possible 
  to 
  maintain 
  an 
  arc 
  between 
  rods 
  

   of 
  pure 
  tellurium. 
  The 
  small 
  spectrograph 
  showed 
  that, 
  in 
  

   addition 
  to 
  the 
  ultra-violet 
  lines, 
  the 
  arc 
  formed 
  at 
  the 
  instant 
  

   of 
  breaking 
  the 
  circuit 
  radiates 
  a 
  continuous 
  spectrum 
  between 
  

   the 
  limits 
  X 
  3300 
  and 
  X 
  4800. 
  This 
  accounts 
  in 
  part 
  only 
  for 
  

   the 
  visible 
  light 
  mentioned 
  above. 
  It 
  seems 
  to 
  come 
  from 
  the 
  

   vapor 
  and 
  not 
  from 
  the 
  electrodes 
  directly. 
  However, 
  we 
  

   have 
  not 
  fully 
  proved 
  this 
  point. 
  If 
  this 
  continuous 
  spectrum 
  

   is 
  really 
  made 
  up 
  of 
  bands 
  then 
  they 
  are 
  too 
  fine 
  and 
  uniform 
  

   to 
  be 
  resolved 
  by 
  the 
  small 
  grating. 
  The 
  intensity 
  of 
  the 
  con- 
  

   tinuous 
  spectrum 
  was 
  not 
  sufficient 
  to 
  justify 
  trying 
  to 
  record 
  

   it 
  with 
  the 
  largest 
  spectrograph. 
  With 
  this 
  instrument 
  the 
  arc 
  

   was 
  always 
  obtained 
  by 
  putting 
  lumps 
  of 
  the 
  metal 
  in 
  a 
  shal- 
  

   low 
  hole 
  in 
  the 
  lower, 
  positive, 
  graphite 
  electrode. 
  The 
  arc 
  

   would 
  not 
  burn 
  between 
  the 
  pointed 
  lower 
  end 
  of 
  the 
  negative 
  

   electrode 
  and 
  the 
  large, 
  spheroidal 
  globule 
  of 
  tellurium 
  but 
  it 
  

   would 
  wander 
  around 
  the 
  peripheral 
  line 
  of 
  contact 
  of 
  the 
  

   lower 
  electrode 
  and 
  the 
  globule. 
  The 
  arc 
  is 
  intensely 
  white 
  

   and 
  it 
  shows 
  the 
  various 
  arc-regions 
  (core, 
  mantle, 
  etc.) 
  very 
  

   clearly 
  and 
  beautifully. 
  Of 
  course, 
  when 
  using 
  an 
  arc 
  of 
  

   tellurium 
  in 
  the 
  manner 
  just 
  mentioned, 
  special 
  precautions 
  

   have 
  to 
  be 
  taken 
  to 
  avoid 
  breathing 
  the 
  fumes 
  which 
  are 
  inju- 
  

   rious 
  and 
  very 
  irritating 
  to 
  the 
  nose, 
  throat 
  and 
  lungs. 
  

  

  Lines 
  1 
  to 
  10 
  inclusive 
  were 
  photographed 
  in 
  the 
  second 
  

   order 
  of 
  the 
  largest 
  grating. 
  The 
  iron 
  spectrum 
  was 
  always 
  

   impressed 
  simultaneously 
  with 
  that 
  of 
  tellurium, 
  and 
  care 
  was 
  

   taken 
  to 
  have 
  the 
  grating 
  entirely 
  filled 
  witli 
  light. 
  Also, 
  

   each 
  line 
  was 
  photographed 
  at 
  the 
  center 
  of 
  curvature 
  of 
  the 
  

   grating 
  in 
  order 
  to 
  have 
  the 
  interferometer 
  iron 
  lines 
  dis- 
  

   tributed 
  nearly 
  linearly. 
  The 
  spectrograms 
  for 
  lines 
  1 
  to 
  10 
  

   inclusive 
  were 
  measured 
  either 
  two 
  or 
  three 
  times 
  in 
  one 
  direc- 
  

   tion 
  and 
  then 
  an 
  equal 
  number 
  of 
  times 
  when 
  reversed. 
  The 
  

   same 
  lines 
  were 
  measured 
  on 
  different 
  plates 
  by 
  the 
  two 
  obser- 
  

   vers 
  and 
  the 
  means 
  of 
  the 
  separate 
  wave-lengths 
  are 
  given 
  in 
  

   the 
  above 
  table. 
  In 
  general, 
  the 
  results 
  agreed 
  very 
  closely, 
  

   but, 
  because 
  some 
  of 
  the 
  interferometer 
  lines 
  used 
  have 
  only 
  

   been 
  determined 
  by 
  Fabry 
  and 
  Buisson 
  and 
  also 
  because 
  there 
  

   exists 
  at 
  the 
  present 
  time 
  some 
  doubt 
  as 
  to 
  the 
  constancy 
  of 
  

  

  