﻿96 
  NEW 
  YORK 
  STATE 
  MUSEUM 
  

  

  can 
  be 
  divided, 
  approach 
  the 
  mean, 
  but 
  rather 
  what 
  are 
  the 
  ex- 
  

   treme 
  divergencies 
  from 
  the 
  mean 
  of 
  such 
  shorter 
  periods. 
  By 
  

   this 
  method, 
  any 
  approach 
  to 
  a 
  general 
  law 
  will 
  soon 
  be 
  detected, 
  

   if 
  the 
  extreme 
  divergencies 
  are 
  for.nd 
  gradually 
  to 
  decrease, 
  as 
  

   the 
  subordinate 
  periods 
  into 
  which 
  the 
  record 
  has 
  been 
  divided 
  

   increase 
  in 
  length. 
  

  

  Also, 
  What 
  is 
  the 
  probable 
  accuracy 
  of 
  any 
  record 
  the 
  length 
  of 
  

   which 
  is 
  less 
  than 
  that 
  necessary 
  to 
  give 
  an 
  average 
  which 
  will 
  

   not 
  be 
  materially 
  altered 
  when 
  the 
  record 
  is 
  extended? 
  

  

  Space 
  will 
  not 
  be 
  taken 
  to 
  show 
  Mr 
  Binnie's 
  views 
  in 
  detail, 
  

   for 
  which 
  reference 
  may 
  be 
  made 
  to 
  the 
  abstract 
  in 
  the 
  second 
  

   Hudson 
  report, 
  or, 
  for 
  the 
  complete 
  views, 
  to 
  the 
  paper 
  in 
  the 
  

   Proceedings 
  of 
  the 
  Institution 
  of 
  'Civil 
  Engineers, 
  but 
  assuming 
  

   that 
  the 
  observations 
  are 
  properly 
  made 
  it 
  is 
  stated 
  that 
  " 
  depend- 
  

   ence 
  can 
  be 
  placed 
  on 
  any 
  good 
  record 
  of 
  thirty-five 
  years' 
  dura- 
  

   tion 
  to 
  give 
  a 
  mean 
  rainfall 
  correct 
  within 
  2 
  per 
  cent 
  of 
  the 
  

   truth.'' 
  

  

  Further, 
  it 
  can 
  be 
  stated 
  that 
  for 
  records 
  from 
  twenty 
  years 
  to 
  

   thirty-five 
  years 
  in 
  length, 
  the 
  error 
  may 
  be 
  expected 
  to 
  vary 
  

   from 
  3.25 
  per 
  cent 
  down 
  to 
  2 
  per 
  cent, 
  and 
  that 
  for 
  the 
  shorter 
  

   periods 
  of 
  five, 
  ten, 
  and 
  fifteen 
  years, 
  the 
  probable 
  extreme 
  devia- 
  

   tion 
  from 
  the 
  mean 
  would 
  be 
  15 
  per 
  cent 
  and 
  4.75 
  per 
  cent, 
  

   respectively. 
  

  

  A 
  twenty 
  years' 
  record, 
  therefore, 
  may 
  be 
  expected 
  to 
  show 
  an 
  

   error 
  of 
  3.24 
  per 
  cent. 
  This 
  is 
  about 
  as 
  close 
  as 
  rainfall 
  records 
  

   in 
  this 
  country 
  will 
  agree, 
  as 
  comparatively 
  few 
  are 
  much 
  beyond 
  

   twenty 
  years 
  in 
  length. 
  

  

  In 
  his 
  paiper 
  on 
  Rainfall 
  of 
  the 
  United 
  States, 
  Mr 
  Henry 
  has 
  

   examined 
  this 
  question, 
  using 
  long 
  records 
  at 
  New 
  Bedford, 
  St 
  

   Louis, 
  Philadelphia, 
  Cincinnati, 
  and 
  other 
  places. 
  The 
  rainfall 
  has 
  

   been 
  measured 
  at 
  New 
  Bedford 
  for 
  83 
  consecutive 
  years, 
  and 
  at 
  

   St 
  Louis 
  for 
  60 
  years. 
  For 
  a 
  10-year 
  period 
  Mr 
  Henry 
  found 
  

   the 
  following 
  variations 
  from 
  the 
  normal 
  : 
  At 
  New 
  Bedford 
  + 
  16 
  

   per 
  cent 
  and 
  — 
  11 
  per 
  cent 
  ; 
  at 
  Cincinnati, 
  + 
  20 
  per 
  cent 
  and 
  — 
  

   17 
  per 
  cent; 
  at 
  St 
  Louis, 
  + 
  17 
  per 
  cent 
  and 
  — 
  13 
  per 
  cent; 
  at 
  

   Fort 
  Leavenworth, 
  + 
  16 
  per 
  cent 
  and 
  — 
  18 
  per 
  cent; 
  and 
  at 
  San 
  

  

  