﻿232 
  ANNUAL 
  REPORT 
  SMITHSONIAN 
  INSTITUTION, 
  1922. 
  

  

  a 
  wedge 
  at 
  one 
  end 
  and 
  a 
  screw 
  at 
  the 
  other. 
  One 
  and 
  two 
  foot 
  tubes 
  

   are 
  carried 
  so 
  that 
  it 
  is 
  possible 
  to 
  reach 
  the 
  centers 
  of 
  most 
  pine 
  

   trees. 
  It 
  would 
  not 
  be 
  difficult 
  to 
  develop 
  an 
  instrument 
  much 
  more 
  

   efficient 
  than 
  this 
  and 
  it 
  should 
  be 
  done. 
  Soon 
  a 
  borer 
  will 
  be 
  needed 
  

   to 
  pass 
  through 
  a 
  35-foot 
  tree 
  or 
  to 
  sound 
  the 
  depths 
  of 
  the 
  great 
  

   Tule 
  trees 
  of 
  southern 
  Mexico. 
  

  

  The 
  tools 
  just 
  mentioned 
  are 
  technical, 
  yet 
  in 
  no 
  sense 
  com- 
  

   plex. 
  A 
  measuring 
  instrument 
  has 
  just 
  been 
  completed 
  whose 
  use- 
  

   fulness 
  will 
  be 
  extensive 
  and 
  whose 
  details 
  of 
  construction 
  are 
  too 
  

   complex 
  for 
  present 
  description. 
  It 
  is 
  for 
  measuring 
  the 
  width 
  of 
  

   rings. 
  It 
  makes 
  a 
  record 
  as 
  fast 
  as 
  one 
  can 
  set 
  a 
  micrometer 
  thread 
  

   on 
  successive 
  rings. 
  The 
  record 
  is 
  in 
  the 
  form 
  of 
  a 
  plot 
  drawn 
  

   in 
  ink 
  to 
  scale 
  on 
  coordinate 
  paper 
  so 
  that 
  the 
  values 
  can 
  be 
  read 
  

   off 
  from 
  it 
  at 
  once 
  for 
  tabulation. 
  This 
  form 
  of 
  record 
  was 
  de- 
  

   sired 
  because 
  individual 
  plots 
  have 
  long 
  been 
  made 
  to 
  help 
  in 
  se- 
  

   lecting 
  the 
  best 
  trees 
  and 
  in 
  studying 
  their 
  relation 
  to 
  topography. 
  

   The 
  instrument 
  as 
  constructed 
  magnifies 
  20, 
  40, 
  or 
  100 
  times, 
  as 
  

   desired. 
  It 
  can 
  be 
  attached 
  to 
  the 
  end 
  of 
  an 
  astronomical 
  telescope 
  

   and 
  used 
  as 
  a 
  recording 
  micrometer 
  capable 
  of 
  making 
  a 
  hundred 
  

   or 
  more 
  settings 
  before 
  reading 
  the 
  values. 
  It 
  seems 
  possible 
  that 
  

   it 
  will 
  have 
  other 
  applications 
  than 
  the 
  ones 
  here 
  mentioned. 
  

  

  Another 
  instrument 
  of 
  entirely 
  different 
  type 
  has 
  been 
  devel- 
  

   oped 
  here 
  since 
  1913. 
  Its 
  general 
  principle 
  has 
  been 
  published 
  and 
  

   will 
  not 
  be 
  repeated, 
  but 
  in 
  the 
  last 
  three 
  years 
  it 
  has 
  been 
  entirely 
  

   rebuilt 
  in 
  a 
  more 
  convenient 
  form 
  through 
  the 
  generosity 
  of 
  Mr. 
  

   Clarence 
  G. 
  White 
  of 
  Eedlands. 
  This 
  instrument 
  is 
  now 
  known 
  as 
  

   the 
  White 
  periodograph. 
  It 
  could 
  be 
  called 
  a 
  cycloscope 
  or 
  cyclo- 
  

   graph. 
  Its 
  purpose 
  is 
  to 
  detect 
  cycles 
  or 
  periods 
  in 
  any 
  plotted 
  

   curve. 
  It 
  differs 
  from 
  previous 
  instruments 
  performing 
  harmonic 
  

   analysis 
  in 
  that 
  it 
  is 
  designed 
  primarily 
  to 
  untangle 
  a 
  complex 
  

   mixture 
  of 
  fairly 
  pronounced 
  periods 
  while 
  others 
  determine 
  the 
  

   constants 
  of 
  a 
  series 
  of 
  harmonic 
  components. 
  For 
  example, 
  the 
  

   periodograph 
  can 
  be 
  applied 
  to 
  a 
  series 
  of 
  rainfall 
  records 
  to 
  find 
  

   if 
  there 
  are 
  any 
  real 
  periods 
  operating 
  in 
  a 
  confused 
  mixture. 
  It 
  

   is 
  also 
  designed 
  to 
  get 
  rid 
  of 
  personal 
  equation 
  and 
  to 
  get 
  results 
  

   quickly. 
  The 
  instrument 
  as 
  reconstructed 
  is 
  far 
  more 
  convenient 
  

   and 
  accurate 
  in 
  use 
  and 
  has 
  already 
  given 
  important 
  results. 
  It 
  

   enables 
  one 
  to 
  see 
  characteristics 
  in 
  tree 
  growth 
  variation 
  which 
  

   are 
  not 
  visible 
  to 
  the 
  unaided 
  eye. 
  It 
  is 
  specially 
  arranged 
  now 
  to 
  

   give 
  what 
  I 
  have 
  called 
  the 
  differential 
  pattern 
  or 
  cyclogram 
  because 
  

   this 
  pattern 
  not 
  only 
  tells 
  the 
  periods 
  or 
  cycles 
  when 
  properly 
  

   read 
  but 
  shows 
  the 
  variations 
  and 
  interferences 
  of 
  cycles 
  and 
  pos- 
  

   sible 
  alternative 
  readings. 
  Tests 
  on 
  the 
  accuracy 
  of 
  solutions 
  by 
  

   this 
  instrument 
  show 
  that 
  its 
  results 
  correspond 
  in 
  precision 
  to 
  

   least-square 
  solutions. 
  

  

  