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  ANNUAL 
  REPORT 
  SMITHSONIAN 
  INSTITUTION, 
  1927 
  

  

  knowledge 
  of 
  the 
  composition 
  and 
  interior 
  structure 
  of 
  the 
  atoms, 
  

   including 
  the 
  phenomena 
  of 
  radioactivity, 
  seems 
  to 
  require 
  a 
  re- 
  

   consideration 
  of 
  the 
  older 
  hypothesis 
  of 
  corpuscular 
  radiation, 
  which 
  

   Newton 
  preferred. 
  In 
  short 
  the 
  emission 
  and 
  the 
  absorption 
  of 
  rays 
  

   seems 
  to 
  demand 
  a 
  discontinuous 
  corpuscular 
  explanation, 
  while 
  the 
  

   propagation 
  of 
  vays 
  no 
  less 
  imperiously 
  demands 
  the 
  acceptance 
  of 
  

   the 
  vehicle 
  of 
  continuous 
  wave-motion. 
  These 
  antagonistic 
  views 
  

   now 
  await 
  reconciliation. 
  

  

  4. 
  MOTIONS 
  OF 
  THE 
  STARS 
  

  

  The 
  observations 
  of 
  such 
  men 
  as 
  Bradley 
  of 
  Oxford, 
  the 
  great 
  

   Astronomer 
  Royal, 
  and 
  all 
  of 
  his 
  successors 
  who 
  have 
  measured 
  ac- 
  

   curately 
  the 
  positions 
  of 
  the 
  stars, 
  form 
  a 
  precious 
  heritage. 
  They 
  

   have 
  rendered 
  their 
  makers' 
  names 
  immortal. 
  For 
  it 
  is 
  by 
  comparing 
  

   these 
  early 
  star 
  positions 
  with 
  the 
  corresponding 
  ones 
  of 
  to-day, 
  

   that 
  a 
  knowledge 
  of 
  the 
  angular 
  displacements, 
  called 
  proper 
  mo- 
  

   tions 
  of 
  the 
  stars, 
  is 
  determined. 
  All 
  the 
  stars, 
  including 
  our 
  sun, 
  

   are 
  on 
  the 
  move. 
  The 
  most 
  rapid 
  star 
  moves 
  over 
  10 
  seconds 
  of 
  arc 
  

   per 
  year. 
  Now 
  that 
  stellar 
  distances, 
  as 
  well 
  as 
  proper 
  motions, 
  

   have 
  become 
  known, 
  these 
  angular 
  displacements 
  are 
  easily 
  con- 
  

   verted 
  into 
  linear 
  velocities, 
  though 
  of 
  course 
  seen 
  in 
  projection 
  on 
  

   the 
  celestial 
  sphere. 
  

  

  Within 
  the 
  past 
  30 
  years 
  another 
  element 
  of 
  stellar 
  motion 
  has 
  

   been 
  added, 
  for 
  the 
  spectroscope 
  has 
  determined 
  for 
  us 
  the 
  rates 
  

   of 
  approach 
  or 
  recession 
  of 
  several 
  thousand 
  stars. 
  This, 
  too, 
  is 
  

   but 
  partial 
  knowledge, 
  lor 
  it 
  gives 
  only 
  the 
  component 
  of 
  a 
  star's 
  true 
  

   motion, 
  relative 
  to 
  the 
  earth, 
  which 
  is 
  projected 
  upon 
  a 
  radius 
  of 
  the 
  

   celestial 
  sphere. 
  Yet 
  when 
  the 
  proper 
  motions 
  and 
  the 
  radial 
  mo- 
  

   tions 
  of 
  the 
  stars 
  are 
  combined, 
  as 
  they 
  can 
  now 
  be, 
  we 
  obtain 
  the 
  

   true 
  motions 
  of 
  the 
  stars 
  in 
  space, 
  relative 
  to 
  the 
  earth, 
  or 
  if 
  w^e 
  

   prefer, 
  to 
  the 
  sun. 
  The 
  sun 
  moves 
  about 
  12 
  7nUes 
  per 
  second, 
  and 
  

   other 
  star 
  velocities 
  range 
  frotn 
  5 
  to 
  100 
  mUes 
  per 
  second. 
  

  

  A 
  large 
  number 
  of 
  true 
  space 
  motions 
  were 
  computed 
  a 
  few 
  years 
  

   ago 
  by 
  Stromberg, 
  with 
  the 
  result 
  of 
  revealing 
  a 
  great 
  coimnon 
  high- 
  

   way, 
  along 
  which 
  not 
  only 
  tJie 
  vaHous 
  groups 
  of 
  stars 
  of 
  different 
  

   spectral 
  types, 
  tut 
  the 
  great 
  star 
  clusters, 
  and 
  even 
  the 
  spiral 
  nehu- 
  

   Im, 
  seemed 
  to 
  he 
  moving 
  with 
  reference 
  to 
  ov/r 
  sun. 
  The 
  phenom- 
  

   enon 
  has 
  been 
  compared 
  by 
  Adams 
  to 
  the 
  flights 
  of 
  a 
  number 
  of 
  

   swarms 
  of 
  bees, 
  which, 
  fortuitously, 
  had 
  chosen 
  a 
  common 
  path 
  for 
  

   their 
  migrations. 
  Individual 
  swarms 
  would 
  fly 
  at 
  unequal 
  rates, 
  

   and 
  individual 
  bees 
  at 
  cross 
  directions 
  to 
  the 
  common 
  course, 
  so 
  that 
  

   a 
  wide 
  dispersion 
  of 
  swarms 
  and 
  individuals 
  would 
  appear. 
  Yet 
  on 
  

   the 
  whole 
  the 
  common 
  course 
  would 
  predominate. 
  

  

  