﻿188 
  

  

  ANNUAL 
  REPORT 
  SMITHSONIAN 
  INSTITUTION, 
  192 
  9 
  

  

  but 
  for 
  the 
  much 
  fainter 
  limit 
  in 
  the 
  last 
  line, 
  the 
  ratio 
  is 
  more 
  than 
  

   40 
  to 
  1. 
  

  

  The 
  general 
  crowding 
  of 
  stars 
  toward 
  the 
  Milky 
  Way 
  has 
  been 
  

   known 
  since 
  the 
  time 
  of 
  the 
  Herschels, 
  but 
  the 
  relatively 
  great 
  con- 
  

   centration 
  shown 
  by 
  the 
  faint 
  stars, 
  although 
  long 
  suspected, 
  was 
  

   first 
  definitely 
  established 
  only 
  a 
  dozen 
  years 
  ago 
  by 
  counts 
  made 
  at 
  

   Mount 
  Wilson. 
  That 
  so 
  conspicuous 
  a 
  feature 
  of 
  the 
  distribution 
  

   could 
  remain 
  long 
  in 
  doubt 
  illustrates 
  the 
  uncertainty 
  attached 
  to 
  

   the 
  magnitude 
  scale 
  then 
  available. 
  This, 
  it 
  was 
  feared, 
  might 
  be 
  

   affected 
  by 
  an 
  errof 
  depending 
  on 
  distance 
  from 
  the 
  Milky 
  Way, 
  which 
  

   would 
  modify 
  the 
  relative 
  numbers 
  of 
  stars 
  counted 
  in 
  the 
  Milky 
  

   Way 
  and 
  elsewhere, 
  and 
  hence 
  render 
  any 
  es|}imate 
  of 
  the 
  concentra- 
  

   tion 
  uncertain. 
  

  

  Let 
  us 
  now 
  try 
  to 
  picture 
  what 
  these 
  peculiarities 
  in 
  the 
  counts 
  of 
  

   stars 
  mean. 
  Table 
  I 
  shows 
  that 
  each 
  extension 
  of 
  the 
  counts 
  over 
  an 
  

   additional 
  magnitude 
  increases 
  the 
  total 
  number 
  of 
  stars 
  visible 
  in 
  

   any 
  direction 
  from 
  two 
  to 
  three 
  times. 
  The 
  exact 
  increase 
  is 
  import- 
  

   ant 
  and 
  is 
  therefore 
  shown 
  in 
  Table 
  II 
  in 
  detail 
  for 
  dift'erent 
  parts 
  of 
  

   the 
  sky. 
  The 
  quantities 
  in 
  this 
  table 
  are 
  nothing 
  but 
  the 
  ratios 
  of 
  

   the 
  numbers 
  standing 
  above 
  each 
  other 
  in 
  Table 
  I. 
  Thus 
  from 
  the 
  

   second 
  column 
  of 
  Table 
  I, 
  0.0449/0.0156 
  = 
  2.88; 
  0.0128/0.0449 
  = 
  2.85, 
  

   etc. 
  The 
  several 
  quotients 
  2.88, 
  2.85, 
  etc., 
  appear 
  in 
  succession 
  in 
  

   the 
  second 
  column 
  of 
  Table 
  II, 
  while 
  similar 
  ratios 
  for 
  other 
  parts 
  of 
  

   the 
  sky 
  are 
  in 
  the 
  remaining 
  columns. 
  These 
  ratios 
  vary 
  smoothly 
  

   over 
  the 
  sky, 
  and 
  range 
  from 
  about 
  3 
  for 
  bright 
  stars 
  near 
  the 
  Milky 
  

   Way 
  to 
  1.4 
  for 
  faint 
  stars 
  at 
  90° 
  distance 
  from 
  the 
  galactic 
  circle. 
  

  

  Table 
  II. 
  — 
  Star 
  ratios 
  

  

  [Factors 
  by 
  which 
  total 
  numbers 
  of 
  stars 
  coimted 
  to 
  limiting 
  

   magnitude 
  m 
  are 
  multiplied 
  when 
  the 
  counts 
  are 
  extended 
  

   one 
  magnitude] 
  

  

  