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  Hutchins 
  — 
  Adjustment 
  of 
  the 
  Quartz 
  Spectrograph. 
  

  

  Art. 
  XXXIII. 
  — 
  Adjustment 
  of 
  the 
  Quartz 
  Spectrograph; 
  

   by 
  C. 
  C. 
  Hutchins. 
  

  

  The 
  most 
  common 
  form 
  of 
  quartz 
  spectrograph 
  is 
  con- 
  

   structed 
  with 
  a 
  single 
  Cornu 
  prism 
  with 
  simple 
  collimating 
  

   and 
  camera 
  lenses 
  of 
  right 
  and 
  left 
  rotation, 
  and 
  is 
  the 
  form 
  to 
  

   which 
  the 
  following 
  remarks 
  apply. 
  It 
  is 
  an 
  extremely 
  use- 
  

   ful 
  type 
  of 
  instrument 
  for 
  recording 
  the 
  complete 
  spectrum 
  

   easily 
  accessible 
  to 
  photography, 
  and 
  in 
  the 
  ultra-violet 
  has 
  a 
  

   resolving 
  power 
  only 
  exceeded 
  by 
  a 
  large 
  grating. 
  It 
  would 
  

   doubtless 
  find 
  more 
  extended 
  use 
  were 
  it 
  not 
  for 
  the 
  very 
  

   tedious 
  operation 
  of 
  putting 
  it 
  into 
  perfect 
  adjustment, 
  com- 
  

   plete 
  directions 
  for 
  which 
  do 
  not 
  seem 
  to 
  be 
  easily 
  accessible. 
  

   Eder,* 
  who 
  had 
  the 
  advice 
  and 
  assistance 
  of 
  Schumann 
  in 
  the 
  

   construction 
  of 
  his 
  apparatus, 
  after 
  giving 
  incomplete 
  direc- 
  

   tions 
  for 
  adjustment 
  dismisses 
  the 
  matter 
  with 
  the 
  remark 
  that 
  : 
  

   " 
  Die 
  Ermittlung 
  der 
  zweckdienlichsten 
  gegenseitigen 
  Stel- 
  

   lung 
  von 
  Collimator, 
  Prisma 
  und 
  Platte 
  ist 
  eine 
  zeitraubende 
  

   Arbeit." 
  

  

  One 
  well-known 
  European 
  maker 
  furnishes 
  an 
  instrument 
  

   ready 
  adjusted 
  for 
  use. 
  The 
  writer 
  has 
  examined 
  and 
  used 
  

   two 
  of 
  these, 
  both 
  large 
  and 
  expensive 
  instruments, 
  and 
  has 
  

   found 
  their 
  performance 
  far 
  from 
  satisfactory. 
  The 
  makers 
  

   have 
  in 
  fact 
  not 
  made 
  use 
  of 
  easily 
  available 
  information 
  in 
  

   their 
  design. 
  Owners 
  of 
  such 
  instruments 
  will 
  be 
  glad 
  to 
  

   know 
  that 
  they 
  are 
  capable 
  of 
  great 
  improvement, 
  while 
  those 
  

   having 
  the 
  type 
  in 
  which 
  all 
  adjustments 
  must 
  be 
  made 
  by 
  

   the 
  user, 
  will, 
  it 
  is 
  hoped, 
  have 
  their 
  task 
  considerably 
  light- 
  

   ened 
  by 
  the 
  following 
  directions. 
  

  

  Lens 
  focus. 
  — 
  It 
  is 
  important 
  that 
  the 
  lenses 
  should 
  not 
  be 
  

   of 
  too 
  short 
  focus. 
  For 
  a 
  prism 
  of 
  medium 
  size 
  — 
  say 
  4 
  em 
  high 
  

   by 
  5 
  cm 
  on 
  the 
  face, 
  plano-convex 
  lenses 
  of 
  70 
  cm 
  focus 
  for 
  yel- 
  

   low 
  sodium 
  light 
  are 
  correct, 
  and 
  for 
  the 
  following 
  reasons 
  : 
  

  

  1. 
  If 
  the 
  optical 
  parts 
  are 
  good 
  that 
  focal 
  length 
  of 
  camera 
  

   lens 
  is 
  needed 
  in 
  order 
  to 
  realize 
  upon 
  the 
  photographic 
  plate 
  

   the 
  full 
  resolving 
  power 
  of 
  the 
  prism. 
  

  

  2. 
  With 
  the 
  best 
  adjustment 
  possible 
  the 
  spectrum 
  does 
  not 
  

   lie 
  in 
  a 
  plane 
  but 
  along 
  a 
  diacaustic 
  curve 
  to 
  which 
  the 
  plate 
  

   must 
  conform, 
  and 
  with 
  a 
  camera 
  lens 
  of 
  70 
  cm 
  focus 
  the 
  result- 
  

   ing 
  curvature 
  is 
  about 
  as 
  great 
  as 
  the 
  ordinary 
  commercial 
  

   plate 
  will 
  bear 
  without 
  danger 
  of 
  breaking, 
  — 
  in 
  fact 
  it 
  is 
  safer 
  

   to 
  sort 
  out 
  any 
  very 
  thick 
  plates 
  and 
  to 
  use 
  them 
  for 
  other 
  

   purposes. 
  

  

  The 
  plate 
  holder. 
  — 
  As 
  is 
  well 
  known, 
  the 
  plate 
  makes 
  an 
  

   angle 
  of 
  about 
  25° 
  with 
  the 
  axis 
  of 
  the 
  camera 
  lens, 
  and 
  should 
  

  

  * 
  Beitrage 
  zur 
  Spectralanalyse. 
  

  

  