﻿F. 
  H. 
  Bigelov:) 
  — 
  Internationcd 
  Cloud 
  Work. 
  44:1 
  

  

  respectively 
  in 
  each 
  district, 
  for 
  winter 
  and 
  also 
  for 
  summer, 
  a 
  

   set 
  of 
  composite 
  charts 
  was 
  constructed 
  by 
  placing 
  a 
  transparent 
  

   sheet 
  of 
  paper 
  over 
  a 
  series 
  of 
  the 
  maps, 
  selected 
  to 
  show 
  the 
  

   same 
  weather 
  type 
  for 
  each 
  district, 
  and 
  tracing 
  in 
  the 
  arrows, 
  

   from 
  which 
  finally 
  a 
  set 
  of 
  resultant 
  vectors 
  for 
  equal 
  squares 
  

   was 
  computed 
  by 
  counting 
  the 
  number 
  of 
  compass 
  point 
  direc- 
  

   tions 
  thus 
  recorded. 
  From 
  40 
  to 
  70 
  maps 
  were 
  used 
  in 
  making 
  

   each 
  chart, 
  and 
  the 
  resulting 
  vectors 
  were 
  reduced 
  to 
  an 
  aver- 
  

   age 
  of 
  40 
  vectors 
  in 
  each 
  square. 
  If 
  the 
  frequency 
  of 
  

   direction 
  is 
  proportional 
  to 
  the 
  prevailing 
  movement 
  of 
  the 
  air, 
  

   then 
  we 
  obtain 
  a 
  chart 
  of 
  relative 
  motions 
  in 
  all 
  parts 
  of 
  the 
  

   high 
  and 
  low 
  areas. 
  The 
  result 
  is 
  most 
  instructive, 
  in 
  many 
  

   respects, 
  of 
  which 
  a 
  few 
  are 
  mentioned. 
  The 
  wind 
  and 
  the 
  

   lower 
  cloud 
  circulation 
  up 
  to 
  the 
  strato-cumulus 
  type 
  are 
  quite 
  

   the 
  same 
  in 
  form, 
  though 
  the 
  cloud 
  level 
  is 
  rather 
  more 
  

   rounded; 
  this 
  movement 
  is 
  very 
  independent 
  of 
  the 
  upper 
  

   cloud 
  region, 
  which 
  is 
  due 
  eastward, 
  or 
  only 
  a 
  little 
  sinuous 
  over 
  

   the 
  highs 
  and 
  lows. 
  This 
  is 
  true 
  of 
  ordinary 
  cyclones, 
  but 
  in 
  

   the 
  case 
  of 
  hurricanes 
  for 
  the 
  South 
  Atlantic 
  States 
  the 
  penetra- 
  

   tion 
  of 
  the 
  lower 
  circulation 
  into 
  the 
  higher 
  is 
  very 
  pronounced, 
  

   showing 
  a 
  much 
  deeper 
  disturbance 
  of 
  the 
  air. 
  Cyclones 
  are 
  

   very 
  thin, 
  only 
  2 
  or 
  3 
  miles 
  deep, 
  while 
  hurricanes 
  are 
  certainly 
  

   5 
  or 
  6 
  miles 
  deep. 
  The 
  anticyclonic 
  and 
  cyclonic 
  areas 
  are 
  

   hardly 
  to 
  be 
  considered 
  as 
  centers 
  of 
  motion 
  except 
  in 
  the 
  very 
  

   lowest 
  strata, 
  since 
  currents 
  of 
  air 
  blow 
  directly 
  across 
  them 
  

   from 
  west 
  to 
  east, 
  even 
  in 
  the 
  cumulus 
  region 
  of 
  the 
  Rocky 
  

   Mountain 
  districts. 
  It 
  is 
  shown 
  that 
  remarkably 
  long 
  streams 
  

   of 
  air, 
  as 
  from 
  the 
  North 
  Pacific 
  to 
  the 
  Lake 
  region, 
  and 
  from 
  

   the 
  Gulf 
  of 
  Mexico 
  to 
  the 
  Lake 
  region, 
  counterflow 
  against 
  

   each 
  to 
  form 
  the 
  cyclonic 
  circulations. 
  We 
  cannot 
  consider 
  

   these 
  to 
  be 
  due 
  to 
  vertical 
  convections 
  drawing 
  in 
  these 
  distant 
  

   masses 
  of 
  air 
  by 
  indraft, 
  since 
  the 
  vertical 
  component 
  ceases 
  at 
  

   2 
  or 
  3 
  miles 
  high. 
  Rather 
  the 
  great 
  horizontal 
  convections 
  of 
  

   the 
  lower 
  strata, 
  caused 
  by 
  the 
  interchange 
  of 
  air 
  between 
  the 
  

   polar 
  and 
  the 
  tropic 
  zones, 
  produce 
  counter 
  currents 
  at 
  the 
  

   cyclone 
  centers, 
  which 
  develop 
  vortices 
  discharging 
  upward 
  

   into 
  the 
  permanent 
  eastward 
  drift. 
  The 
  study 
  of 
  these 
  normal 
  

   charts 
  of 
  circulation 
  will 
  tend 
  to 
  correct 
  some 
  prevailing 
  erro- 
  

   neous 
  conceptions 
  regarding 
  the 
  structure 
  of 
  cyclones. 
  It 
  will 
  

   surprise 
  many 
  to 
  see 
  that 
  a 
  strong 
  and 
  warm 
  current 
  in 
  the 
  

   cumulus 
  region 
  blows 
  directlyfrom 
  the 
  Pacific 
  Ocean 
  eastward 
  

   across 
  a 
  cold-wave 
  area, 
  showing 
  that 
  cold 
  waves 
  are 
  thin 
  masses 
  

   of 
  air, 
  hardly 
  one 
  mile 
  thick, 
  produced 
  by 
  surface 
  radiation 
  on 
  

   the 
  eastern 
  or 
  lea 
  side 
  of 
  the 
  mountains. 
  It 
  is 
  no 
  less 
  remark- 
  

   able 
  to 
  find 
  that 
  the 
  center 
  of 
  the 
  high 
  areas 
  formed 
  by 
  the 
  

   isobars 
  drawn 
  from 
  reductions 
  made 
  by 
  the 
  Hazen 
  method, 
  now 
  

   employed 
  by 
  the 
  Weather 
  Bureau, 
  is 
  often 
  500 
  miles 
  distant 
  

  

  