﻿196 
  

  

  ANNUAL 
  REPORT 
  SMITHSONIAN 
  INSTITUTION, 
  192 
  9 
  

  

  to 
  the 
  Milky 
  Way, 
  but 
  about 
  a 
  plane 
  slightly 
  inclined 
  thereto. 
  Thus 
  

   far 
  we 
  have 
  thought 
  of 
  the 
  stars 
  as 
  all 
  tending 
  to 
  crowd 
  toward 
  the 
  

   Milky 
  Way; 
  but 
  now 
  apparently 
  we 
  must 
  admit 
  that 
  some 
  of 
  them 
  

   cluster 
  about 
  another 
  circle, 
  a 
  little 
  tilted 
  with 
  respect 
  to 
  the 
  Milky 
  

   Way. 
  Since 
  we 
  sometimes 
  speak 
  of 
  the 
  Milky 
  Way 
  itself 
  as 
  the 
  gal- 
  

   axy, 
  we 
  call 
  this 
  new 
  circle 
  the 
  secondary 
  galaxy. 
  

  

  The 
  small 
  differences 
  existing 
  between 
  curves 
  for 
  equal 
  and 
  opposite 
  

   latitudes 
  may 
  be 
  used 
  to 
  compute 
  the 
  amount 
  and 
  the 
  direction 
  of 
  the 
  

   tilt 
  of 
  the 
  secondary 
  galaxy; 
  and 
  since 
  several 
  pairs 
  of 
  curves 
  are 
  

   available 
  for 
  each 
  limiting 
  magnitude, 
  a 
  number 
  of 
  independent 
  solu- 
  

   tions 
  may 
  be 
  made, 
  the 
  accordance 
  of 
  which 
  will 
  test 
  the 
  reality 
  of 
  the 
  

   results. 
  Since 
  the 
  existence 
  of 
  a 
  secondary 
  galaxy 
  modifies 
  slightly 
  

   the 
  longitudes 
  already 
  found 
  for 
  the 
  center 
  of 
  the 
  system, 
  these 
  must 
  

   be 
  redetermined 
  when 
  the 
  position 
  of 
  the 
  secondary 
  galaxy 
  is 
  calcu- 
  

   lated. 
  The 
  complete 
  results 
  for 
  limiting 
  magnitude 
  16 
  are 
  shown 
  in 
  

  

  Table 
  IV. 
  

  

  Table 
  IV 
  

  

  Here 
  again, 
  the 
  agreement 
  in 
  values 
  derived 
  from 
  different 
  latitudes 
  

   is 
  all 
  that 
  can 
  be 
  expected. 
  The 
  mean 
  for 
  the 
  tilt 
  is 
  4°, 
  in 
  longitude 
  

   357°, 
  with 
  a 
  scatter 
  in 
  the 
  individual 
  values 
  so 
  small 
  as 
  to 
  leave 
  no 
  

   doubt 
  as 
  to 
  the 
  general 
  result. 
  

  

  When 
  we 
  extend 
  the 
  calculation 
  to 
  other 
  limiting 
  magnitudes, 
  

   however, 
  we 
  find 
  that 
  the 
  secondary 
  galaxy 
  is 
  no 
  more 
  a 
  fixed 
  thing 
  

   than 
  is 
  the 
  direction 
  of 
  the 
  center 
  of 
  the 
  system, 
  and, 
  like 
  the 
  direction 
  

   of 
  the 
  center, 
  depends 
  on 
  the 
  limit 
  of 
  brightness 
  to 
  which 
  the 
  stars 
  

   have 
  been 
  counted. 
  From 
  counts 
  to 
  the 
  eighteenth 
  magnitude 
  we 
  

   find 
  a 
  secondary 
  galaxy 
  which 
  deviates 
  but 
  little 
  from 
  the 
  Milky 
  

   Way 
  ; 
  and 
  had 
  we 
  counts 
  to 
  the 
  twenty-first 
  or 
  twenty-second 
  magni- 
  

   tude, 
  we 
  should 
  probably 
  find 
  practical 
  coincidence. 
  Counts 
  to 
  other 
  

   limits 
  show, 
  however, 
  a 
  very 
  appreciable 
  departure 
  and 
  a 
  progressive 
  

   change 
  in 
  the 
  position 
  of 
  the 
  secondary 
  galaxy, 
  which 
  attains 
  its 
  

   greatest 
  inclination 
  to 
  the 
  Milky 
  Way 
  when 
  only 
  bright 
  stars 
  are 
  

   included 
  in 
  the 
  calculation. 
  Figure 
  2 
  illustrates 
  the 
  results 
  found 
  

   from 
  the 
  Mount 
  Wilson 
  counts, 
  and 
  some 
  by 
  other 
  observers 
  from 
  

   other 
  data, 
  plotted 
  to 
  show 
  the 
  changes 
  in 
  the 
  direction 
  of 
  the 
  center 
  

   (L) 
  and 
  in 
  the 
  position 
  of 
  the 
  secondary 
  galaxy 
  (p, 
  tilt 
  of 
  plane; 
  

   Lo, 
  direction 
  of 
  tilt). 
  

  

  These 
  calculations 
  afford 
  opportunity 
  for 
  a 
  closer 
  comparison 
  

   of 
  the 
  numbers 
  of 
  stars 
  on 
  opposite 
  sides 
  of 
  the 
  Milky 
  Way. 
  Ex- 
  

  

  