﻿ANNUAL 
  KINGS 
  OF 
  TREES 
  — 
  DOUGLASS. 
  235 
  

  

  It 
  is 
  to 
  be 
  noted 
  that 
  it 
  appears 
  in 
  regions 
  whose 
  trees 
  have 
  an 
  

   abundance 
  of 
  moisture, 
  and 
  it 
  thus 
  appears 
  to 
  be 
  a 
  wet-climate 
  

   phenomenon. 
  

  

  . 
  But 
  the 
  correlations 
  do 
  not 
  stop 
  at 
  rain 
  and 
  sun-spot 
  periodicity. 
  

   The 
  pines 
  of 
  northern 
  Arizona, 
  which 
  are 
  so 
  sensitive 
  to 
  rainfall, 
  

   show 
  a 
  strong 
  half 
  sun-spot 
  period. 
  And 
  on 
  testing 
  it 
  one 
  finds 
  

   that 
  the 
  rainfall 
  does 
  the 
  same 
  and 
  that 
  these 
  variations 
  are 
  almost 
  

   certainly 
  related 
  to 
  corresponding 
  temperature 
  variations 
  and 
  to 
  the 
  

   solar 
  period. 
  Thus, 
  the 
  Arizona 
  trees 
  are 
  related 
  to 
  the 
  weather, 
  and 
  

   the 
  weather 
  is 
  related 
  in 
  a 
  degree, 
  at 
  least, 
  to 
  the 
  sun. 
  Thus, 
  we 
  

   find 
  evidence 
  in 
  forest 
  trees 
  that 
  the 
  11-year 
  sun-spot 
  period 
  pre- 
  

   vails 
  in 
  widely 
  different 
  localities 
  and 
  in 
  many 
  places 
  constitutes 
  

   the 
  major 
  variation. 
  This 
  introduces 
  us 
  to 
  the 
  study 
  of 
  periodic 
  

   effects 
  in 
  general. 
  

  

  VII. 
  CYCLES. 
  

  

  Considering 
  first 
  that 
  cycles, 
  as 
  we 
  have 
  just 
  shown, 
  are 
  revealed 
  

   in 
  tree 
  growth, 
  second, 
  that 
  the 
  trees 
  give 
  us 
  accurate 
  historic 
  rec- 
  

   ords 
  for 
  hundreds 
  and 
  even 
  thousands 
  of 
  years, 
  and 
  third, 
  that 
  

   simple 
  cycles 
  or 
  even 
  some 
  more 
  complex 
  function 
  could 
  give 
  a 
  

   basis 
  for 
  long 
  range 
  weather 
  forecasting, 
  we 
  recognize 
  the 
  vital 
  

   importance 
  of 
  this 
  elemental 
  part 
  of 
  the 
  story 
  told 
  by 
  the 
  trees. 
  

   It 
  was 
  exactly 
  for 
  this 
  purpose 
  that 
  the 
  periodograph 
  was 
  designed 
  

   and 
  constructed 
  and 
  some 
  10-score 
  curves 
  have 
  been 
  cut 
  out 
  for 
  

   analysis, 
  after 
  minute 
  preparation 
  of 
  the 
  very 
  best 
  yearly 
  values. 
  

   In 
  fact 
  the 
  major 
  time 
  for 
  two 
  years 
  has 
  been 
  given 
  to 
  this 
  prepara- 
  

   tion 
  of 
  material. 
  It 
  is 
  hardly 
  done 
  yet, 
  but 
  it 
  is 
  far 
  enough 
  along 
  

   to 
  anticipate 
  its 
  careful 
  study 
  in 
  the 
  near 
  future. 
  Our 
  present 
  view 
  

   may 
  be 
  profoundly 
  modified, 
  but 
  it 
  is 
  safe 
  to 
  say 
  that 
  the 
  sun-spot 
  

   cycle 
  and 
  its 
  double 
  and 
  triple 
  value 
  are 
  very 
  general. 
  The 
  double 
  

   value, 
  about 
  22 
  years, 
  has 
  persisted 
  in 
  Arizona 
  for 
  500 
  years, 
  and 
  

   in 
  some 
  north 
  European 
  localities 
  for 
  the 
  century 
  and 
  a 
  half 
  cov- 
  

   ered 
  by 
  our 
  tree 
  groups. 
  The 
  triple 
  period, 
  essentially 
  Bruckner's 
  

   cycle, 
  has 
  operated 
  in 
  Arizona 
  for 
  the 
  last 
  200 
  years 
  and 
  in 
  Norway 
  

   for 
  nearly 
  400 
  at 
  least. 
  A 
  100-year 
  cycle 
  is 
  very 
  prominent 
  

   throughout 
  the 
  3,000 
  years 
  of 
  sequoia 
  record 
  and 
  also 
  in 
  the 
  500 
  

   years 
  of 
  yellow 
  pine. 
  A 
  hypothesis 
  covering 
  all 
  these 
  sun-spot 
  mul- 
  

   Hples 
  will 
  be 
  tested 
  out 
  in 
  the 
  coming 
  months. 
  Should 
  a 
  real 
  

   explanation 
  be 
  found 
  a 
  step 
  will 
  have 
  been 
  made 
  toward 
  long-range 
  

   prediction 
  and 
  an 
  understanding 
  of 
  the 
  relationship 
  of 
  the 
  weather 
  

   and 
  the 
  sun. 
  Other 
  periods,, 
  however, 
  than 
  the 
  multiples 
  of 
  the 
  

   sun-spot 
  period 
  do 
  occur, 
  and 
  general 
  analysis 
  shows 
  that 
  different 
  

   centuries 
  are 
  characterized 
  by 
  different 
  combinations 
  of 
  climatic 
  

   cycles. 
  This 
  suggests 
  to 
  us 
  a 
  great 
  and 
  interesting 
  problem. 
  If 
  we 
  

  

  