﻿94 
  ANNUAL 
  REPORT 
  SMITHSONIAN 
  INSTITUTION, 
  192 
  9 
  

  

  on 
  the 
  preparation 
  and 
  standardization 
  of 
  apparatus. 
  Details 
  

   follow. 
  

  

  (a) 
  Periodicities 
  in 
  solar 
  variation. 
  — 
  Observations 
  at 
  Montezuma, 
  

   in 
  Chile, 
  had 
  been 
  reduced 
  to 
  a 
  consistent 
  and 
  definitive 
  system 
  several 
  

   years 
  since. 
  This 
  system 
  requires 
  no 
  computations 
  beyond 
  those 
  

   which 
  the 
  observers 
  make 
  regularly 
  in 
  the 
  field. 
  Telegrams 
  in 
  code 
  

   are 
  received 
  daily 
  from 
  Montezuma, 
  and 
  when 
  decoded 
  are 
  communi- 
  

   cated 
  to 
  the 
  United 
  States 
  Weather 
  Bureau, 
  which 
  publishes 
  on 
  the 
  

   Washington 
  daily 
  weather 
  map 
  the 
  solar 
  constant 
  value 
  observed 
  24 
  

   hours 
  previously 
  at 
  Montezuma. 
  

  

  In 
  November, 
  1928, 
  Doctor 
  Abbot 
  assembled 
  the 
  monthly 
  mean 
  

   solar 
  constant 
  values 
  of 
  101 
  consecutive 
  months 
  ending 
  with 
  October, 
  

   1928, 
  and 
  plotted 
  them 
  in 
  the 
  form 
  of 
  a 
  curve. 
  This 
  curve 
  Dr. 
  

   Dayton 
  C. 
  Miller, 
  of 
  Cleveland, 
  was 
  kind 
  enough 
  to 
  analyze 
  by 
  means 
  

   of 
  his 
  ingenious 
  and 
  accurate 
  machine, 
  so 
  as 
  to 
  bring 
  out 
  the 
  first 
  30 
  

   harmonic 
  constituents, 
  which, 
  combined, 
  approximately 
  represent 
  the 
  

   original 
  curve. 
  

  

  From 
  a 
  previous 
  analysis 
  of 
  77 
  months, 
  made 
  in 
  1926, 
  it 
  had 
  

   appeared 
  that 
  periods 
  of 
  about 
  26, 
  15, 
  and 
  11 
  months 
  and 
  the 
  sub- 
  

   multiples 
  of 
  these 
  periods 
  were 
  all 
  the 
  periods 
  under 
  26 
  months 
  that 
  

   seemed 
  to 
  have 
  continuous 
  existence 
  in 
  the 
  solar 
  variation. 
  Accord- 
  

   ingly, 
  the 
  interval 
  of 
  101 
  months 
  had 
  been 
  purposely 
  chosen 
  as 
  nearly 
  

   a 
  common 
  multiple, 
  so 
  that 
  if 
  these 
  periods 
  were 
  still 
  persistent 
  they 
  

   might 
  be 
  brought 
  out 
  as 
  approximately 
  the 
  fourth, 
  the 
  seventh, 
  and 
  

   the 
  ninth 
  harmonics, 
  with 
  their 
  overtones. 
  

  

  Figure 
  2 
  shows 
  the 
  result 
  of 
  this 
  analysis. 
  The 
  zigzag 
  line 
  A 
  

   represents 
  the 
  original 
  monthly 
  mean 
  of 
  observations, 
  and 
  the 
  30 
  

   sinuous 
  curves 
  below 
  are 
  the 
  harmonics. 
  Until 
  a 
  longer 
  interval 
  of 
  

   observation 
  shall 
  be 
  available 
  for 
  analysis, 
  it 
  is 
  not 
  considered 
  desir- 
  

   able 
  to 
  discuss 
  periodicities 
  longer 
  than 
  -j- 
  months. 
  The 
  reader 
  

  

  will 
  perceive 
  that 
  if 
  we 
  therefore 
  neglect 
  the 
  march 
  of 
  the 
  first, 
  

   second, 
  and 
  third 
  harmonics, 
  the 
  fourth, 
  its 
  overtones 
  the 
  eighth, 
  

   twelfth, 
  and 
  sixteenth; 
  the 
  seventh, 
  its 
  overtones 
  the 
  fourteenth, 
  

   twenty-first, 
  and 
  twenty-eighth; 
  and 
  the 
  ninth 
  and 
  its 
  approximate 
  

   overtones 
  the 
  nineteenth 
  and 
  twenty-seventh 
  are 
  really 
  the 
  most 
  

   prominent 
  features, 
  whereas 
  some 
  of 
  the 
  other 
  harmonics, 
  such 
  as 
  

   the 
  fifth, 
  sixth, 
  tenth, 
  eleventh, 
  thirteenth, 
  seventeenth, 
  eighteenth, 
  

   twentieth, 
  twenty-fourth, 
  twenty-sixth, 
  and 
  twenty-ninth, 
  not 
  in- 
  

   cluded 
  in 
  these 
  three 
  series 
  of 
  overtones, 
  nearly 
  vanish. 
  Indeed, 
  

   apart 
  from 
  those 
  named 
  in 
  connection 
  with 
  the 
  fourth, 
  the 
  seventh, 
  

   and 
  the 
  ninth, 
  only 
  the 
  twelfth, 
  fifteenth, 
  twenty-third, 
  and 
  twenty- 
  

   fifth 
  seem 
  to 
  be 
  of 
  appreciable 
  significance. 
  This 
  suggests 
  that 
  the 
  

   third 
  and 
  its 
  overtones 
  may 
  also 
  have 
  real 
  significance. 
  It 
  is 
  of 
  great 
  

  

  