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  ANNUAL 
  REPORT 
  SMITHSONIAN 
  INSTITUTION, 
  1922. 
  

  

  rings 
  and 
  the 
  rainfall 
  for 
  the 
  corresponding 
  years 
  since 
  1898, 
  when 
  

   the 
  Flagstaff 
  weather 
  station 
  was 
  established. 
  The 
  more 
  detailed 
  

   comparison 
  between 
  rainfall 
  and 
  ring 
  growth 
  was 
  made 
  with 
  Pres- 
  

   cott 
  trees 
  in 
  1911. 
  Some 
  67 
  trees 
  in 
  five 
  groups 
  within 
  10 
  miles 
  

   of 
  Prescott 
  were 
  compared 
  with 
  the 
  rainfall 
  at 
  Whipple 
  Barracks 
  

   and 
  Prescott 
  which 
  had 
  been 
  kept 
  on 
  record 
  since 
  1867. 
  The 
  result 
  

   was 
  very 
  interesting. 
  For 
  most 
  years 
  the 
  tree 
  variations 
  agree 
  

   almost 
  exactly 
  with 
  the 
  rainfall, 
  but 
  here 
  and 
  there 
  is 
  a 
  year 
  or 
  two 
  

   of 
  disagreement. 
  The 
  cause 
  of 
  these 
  variable 
  years 
  will 
  sometime 
  

   be 
  an 
  interesting 
  matter 
  of 
  study. 
  Taken 
  altogether 
  the 
  accuracy 
  

   of 
  the 
  tree 
  as 
  a 
  rain 
  gauge 
  wag 
  70 
  per 
  cent. 
  But 
  a 
  little 
  allowance 
  

   for 
  conservation 
  of 
  moisture 
  raised 
  the 
  accuracy 
  to 
  85 
  per 
  cent, 
  

   which 
  is 
  remarkably 
  good. 
  The 
  actual 
  character 
  of 
  this 
  conserva- 
  

   tion 
  is 
  not 
  evident. 
  At 
  first 
  thought 
  it 
  might 
  be 
  persistence 
  of 
  

   moisture 
  in 
  the 
  ground, 
  but 
  the 
  character 
  of 
  the 
  mathematical 
  

   formula 
  which 
  evaluated 
  it 
  allowed 
  a 
  different 
  interpretation, 
  

   namely, 
  that 
  in 
  a 
  series 
  of 
  poor 
  years 
  the 
  vital 
  activity 
  of 
  the 
  tree 
  

   is 
  lessened. 
  During 
  the 
  dry 
  period, 
  from 
  about 
  1870 
  to 
  1905 
  or 
  

   so, 
  the 
  trees 
  responded 
  each 
  year 
  to 
  the 
  fluctuations 
  in 
  rainfall 
  but 
  

   with 
  less 
  and 
  less 
  spirit. 
  This 
  lessening 
  activity 
  took 
  place 
  at 
  a 
  

   certain 
  rate 
  which 
  the 
  meteorologists 
  call 
  the 
  " 
  accumulated 
  mois- 
  

   ture 
  " 
  curve. 
  This 
  suggested 
  that 
  the 
  conservation 
  was 
  in 
  the 
  tree 
  

   itself. 
  There 
  is 
  much 
  to 
  be 
  done 
  in 
  this 
  comparison 
  between 
  tree 
  

   growth 
  and 
  rainfall, 
  but 
  the 
  obstacle 
  everywhere 
  is 
  the 
  lack 
  of 
  

   rainfall 
  records 
  near 
  the 
  trees 
  and 
  over 
  adequate 
  periods 
  of 
  time. 
  

   The 
  five 
  Prescott 
  groups 
  showed 
  that 
  in 
  a 
  mountainous 
  country 
  near- 
  

   ness 
  was 
  very 
  important. 
  But 
  the 
  nearest 
  records 
  to 
  the 
  sequoias 
  

   are 
  65 
  miles 
  away 
  and 
  at 
  5,000 
  feet 
  lower 
  elevation. 
  The 
  best 
  com- 
  

   parison 
  records 
  for 
  the 
  Oregon 
  Douglas 
  spruce 
  are 
  25 
  miles 
  away. 
  

   It 
  is 
  so 
  nearly 
  everywhere. 
  The 
  real 
  tests 
  must 
  be 
  made 
  with 
  records 
  

   near 
  by. 
  

  

  In 
  1912, 
  while 
  attempting 
  to 
  test 
  this 
  relationship 
  of 
  tree 
  growth 
  

   to 
  rainfall 
  in 
  north 
  Europe, 
  I 
  found 
  that 
  the 
  Scotch 
  pines 
  south 
  

   of 
  the 
  Baltic 
  Sea 
  showed 
  a 
  very 
  strong 
  and 
  beautiful 
  rhythm, 
  

   matching 
  exactly 
  the 
  sun-spot 
  cycle 
  as 
  far 
  back 
  as 
  the 
  trees 
  extended, 
  

   which 
  was 
  close 
  to 
  a 
  century. 
  The 
  same 
  rhythm 
  was 
  evident 
  in 
  the 
  

   trees 
  of 
  Sweden, 
  and 
  perhaps 
  more 
  conspicuous 
  in 
  spruce 
  than 
  

   pine. 
  Near 
  Christiania 
  the 
  pines 
  were 
  too 
  variable 
  to 
  show 
  it, 
  but 
  

   it 
  reappeared 
  on 
  the 
  outer 
  Norwegian 
  coast. 
  To 
  the 
  south 
  near 
  the 
  

   Alps 
  it 
  disappeared, 
  and 
  in 
  the 
  south 
  of 
  England 
  it 
  was 
  uncertain 
  

   but 
  probably 
  there. 
  In 
  this 
  country 
  it 
  shows 
  prominently 
  in 
  Ver- 
  

   mont 
  and 
  Oregon, 
  but 
  the 
  two 
  American 
  maxima 
  come 
  one 
  to 
  three 
  

   years 
  in 
  advance 
  of 
  the 
  sun-spot 
  maxima. 
  There 
  is 
  evidently 
  an 
  

   important 
  astronomical 
  relationship 
  whose 
  meaning 
  is 
  not 
  yet 
  clear. 
  

  

  