﻿ANNUAL 
  RINGS 
  OF 
  TREES 
  — 
  DOUGLASS. 
  225 
  

  

  ing, 
  both 
  as 
  to 
  its 
  climate 
  and 
  the 
  number 
  of 
  years 
  involved 
  and 
  

   the 
  order 
  of 
  building. 
  This 
  is 
  anthropology. 
  It 
  will 
  be 
  mentioned 
  

   on 
  a 
  later 
  page. 
  

  

  Viewed 
  through 
  the 
  present 
  perspective, 
  there 
  is 
  one 
  way 
  of 
  

   expressing 
  the 
  entire 
  work 
  which 
  shows 
  more 
  clearly 
  its 
  human 
  

   end, 
  a 
  contact 
  always 
  worth 
  emphasizing. 
  If 
  the 
  study 
  works 
  out 
  

   as 
  it 
  promises, 
  it 
  will 
  give 
  a 
  basis 
  of 
  long-range 
  weather 
  forecasting 
  

   of 
  immense 
  practical 
  value 
  for 
  the 
  future 
  and 
  of 
  large 
  scientific 
  

   value 
  in 
  interpreting 
  the 
  climate 
  of 
  the 
  past. 
  This 
  statement 
  of 
  it 
  

   carries 
  to 
  all 
  a 
  real 
  idea 
  of 
  the 
  central 
  problem. 
  

  

  II. 
  YEARLY 
  IDENTITY 
  OF 
  RINGS. 
  

  

  The 
  one 
  fundamental 
  quality 
  which 
  makes 
  tree 
  rings 
  of 
  value 
  

   in 
  the 
  study 
  of 
  climate 
  is 
  their 
  yearly 
  identity. 
  In 
  other 
  words, 
  

   the 
  ring 
  series 
  reaches 
  its 
  real 
  value 
  when 
  the 
  date 
  of 
  every 
  ring 
  

   can 
  be 
  determined 
  with 
  certainty. 
  This 
  is 
  the 
  quality 
  which 
  is 
  

   often 
  taken 
  for 
  granted 
  without 
  thought 
  and 
  often 
  challenged 
  with- 
  

   out 
  real 
  reason. 
  The 
  climatic 
  nature 
  of 
  a 
  ring 
  is 
  its 
  most 
  ob- 
  

   vious 
  feature. 
  There 
  is 
  a 
  gradual 
  cessation 
  of 
  the 
  activity 
  of 
  the 
  

   tree 
  owing 
  to 
  lowered 
  temperature 
  or 
  diminished 
  water 
  supply. 
  

   This 
  causes 
  the 
  deposition 
  of 
  harder 
  material 
  in 
  the 
  cell 
  walls, 
  pro- 
  

   ducing 
  in 
  the 
  pine 
  the 
  dark 
  hard 
  autumn 
  part 
  of 
  the 
  ring. 
  The 
  

   growth 
  practically 
  stops 
  altogether 
  in 
  winter 
  and 
  then 
  starts 
  off 
  in 
  

   the 
  spring 
  at 
  a 
  very 
  rapid 
  rate 
  with 
  soft 
  white 
  cells. 
  The 
  usual 
  time 
  

   of 
  beginning 
  growth 
  in 
  the 
  spring 
  at 
  Flagstaff, 
  Ariz, 
  (elevation 
  

   7,000 
  feet) 
  , 
  is 
  in 
  late 
  May 
  or 
  June 
  and 
  is 
  best 
  observed 
  by 
  Dr. 
  D. 
  T. 
  

   MacDougal's 
  " 
  Dendrograph,' 
  ' 
  which 
  magnifies 
  the 
  diameter 
  of 
  the 
  

   tree 
  trunk 
  and 
  shows 
  its 
  daily 
  variations. 
  This 
  spring 
  growth 
  de- 
  

   pends 
  upon 
  the 
  precipitation 
  of 
  the 
  preceding 
  winter 
  and 
  the 
  way 
  it 
  

   comes 
  to 
  the 
  tree. 
  Heavy 
  rains 
  have 
  a 
  large 
  run-off 
  and 
  are 
  less 
  bene- 
  

   ficial 
  than 
  snow. 
  The 
  snow 
  melts 
  in 
  the 
  spring 
  and 
  supplies 
  its 
  

   moisture 
  gradually 
  to 
  the 
  roots 
  as 
  it 
  soaks 
  into 
  or 
  moves 
  through 
  the 
  

   ground. 
  There 
  is 
  evidence 
  that 
  if 
  the 
  soil 
  is 
  porous 
  and 
  resting 
  on 
  

   well 
  cracked 
  limestone 
  strata, 
  the 
  moisture 
  passes 
  quickly 
  and 
  the 
  

   effect 
  is 
  transitory, 
  lasting 
  in 
  close 
  proportion 
  to 
  the 
  amount 
  of 
  rain. 
  

   Trees 
  so 
  placed 
  are 
  " 
  sensitive 
  " 
  and 
  give 
  an 
  excellent 
  report 
  of 
  the 
  

   amount 
  of 
  precipitation. 
  Such 
  condition 
  is 
  commonly 
  found 
  in 
  

   northern 
  Arizona 
  over 
  a 
  limestone 
  bed 
  rock. 
  If 
  the 
  bed 
  rock 
  is 
  

   basalt 
  or 
  other 
  igneous 
  material 
  the 
  soil 
  over 
  it 
  is 
  apt 
  to 
  be 
  clay. 
  The 
  

   rock 
  and 
  the 
  clay 
  sometimes 
  hold 
  water 
  until 
  the 
  favorable 
  season 
  is 
  

   past 
  and 
  the 
  tree 
  growth 
  depends 
  in 
  a 
  larger 
  measure 
  on 
  other 
  factors 
  

   than 
  the 
  precipitation. 
  For 
  example, 
  the 
  yellow 
  pines 
  growing 
  in 
  

   the 
  very 
  dry 
  lava 
  beds 
  at 
  Flagstaff 
  show 
  nearly 
  the 
  same 
  growth 
  year 
  

   after 
  year. 
  It 
  is 
  sometimes 
  large, 
  but 
  it 
  has 
  little 
  variation. 
  Such 
  

   growth 
  is 
  " 
  complacent." 
  

  

  