﻿438 
  . 
  F. 
  II. 
  Bigelow 
  — 
  International 
  Cloud 
  Work. 
  

  

  cumulus 
  cloud. 
  In 
  the 
  adiabatic 
  process 
  the 
  ratio 
  z-- 
  is 
  con- 
  

  

  stant 
  in 
  the 
  unsaturated 
  stage, 
  that 
  is 
  from 
  the 
  ground 
  to 
  the 
  

   cloud 
  base, 
  and 
  bj 
  two 
  or 
  three 
  easy 
  approximations, 
  after 
  

   starting 
  with 
  B. 
  t. 
  e. 
  at 
  the 
  ground, 
  we 
  compute 
  B,^. 
  t^. 
  e^ 
  and 
  

   the 
  height 
  h^ 
  of 
  saturation. 
  Now 
  the 
  question 
  is, 
  does 
  this 
  

   computed 
  height 
  h^ 
  agree 
  with 
  the 
  measured 
  height 
  of 
  the 
  

   cumulus 
  base 
  h^ 
  % 
  The 
  result 
  of 
  our 
  work 
  is 
  to 
  show 
  that 
  the 
  

   observed 
  height 
  h^ 
  is 
  greater 
  than 
  Z^,. 
  We 
  must, 
  therefore, 
  

   determine 
  the 
  values 
  B^.t^.e^. 
  at 
  the 
  base 
  of 
  the 
  cloud 
  accu- 
  

  

  rately, 
  and 
  thus 
  find 
  the 
  relation 
  between 
  the 
  adiabatic 
  — 
  and 
  

  

  e 
  . 
  . 
  . 
  "^ 
  

  

  the 
  actual 
  — 
  ^. 
  A 
  considerable 
  number 
  of 
  kite 
  ascensions 
  were 
  

  

  made 
  in 
  the 
  summer 
  of 
  1898 
  by 
  the 
  Weather 
  Bureau, 
  and 
  

   more 
  than 
  100 
  cases 
  occurred 
  in 
  which 
  the 
  B^..tJ..Cf^.h^.. 
  were 
  

   measured 
  by 
  the 
  kite 
  instruments 
  on 
  entering 
  the 
  base 
  of 
  the 
  

   cloud. 
  These 
  have 
  enabled 
  us 
  to 
  study 
  this 
  important 
  ques- 
  

   tion 
  carefully. 
  It 
  may 
  be 
  stated 
  that 
  four 
  distinct 
  ways 
  have 
  

   been 
  developed 
  of 
  finding 
  the 
  temperature 
  quite 
  approximately 
  

   at 
  the 
  cloud 
  base, 
  and 
  hence 
  the 
  vapor 
  tension 
  and 
  the 
  pressure, 
  

   so 
  that 
  for 
  usual 
  conditions, 
  that 
  is 
  to 
  say 
  excepting 
  the 
  

   strongly 
  stratified 
  condition 
  which 
  occurs 
  when 
  currents 
  of 
  

   very 
  different 
  temperatures 
  flow 
  over 
  one 
  another, 
  we 
  can 
  

   compute 
  the 
  pressure 
  at 
  the 
  height 
  of 
  a 
  mile 
  with 
  an 
  error 
  

   usually 
  of 
  ±0 
  02 
  and 
  always 
  of 
  less 
  than 
  ±0*04 
  inch, 
  which 
  

   insures 
  good 
  map 
  drawing 
  at 
  that 
  height. 
  The 
  determination 
  

   of 
  the 
  divergence 
  of 
  the 
  actual 
  from 
  the 
  adiabatic 
  atmosphere 
  

   is 
  valuable 
  in 
  its 
  application 
  to 
  several 
  meteorological 
  problems. 
  

  

  (2) 
  It 
  has 
  been 
  assumed 
  that 
  the 
  value 
  of 
  the 
  ratio 
  z^ 
  

  

  obtained 
  for 
  the 
  base 
  of 
  the 
  cumulus 
  cloud 
  holds 
  true 
  through- 
  

   out 
  the 
  cloud 
  itself, 
  and 
  that 
  in 
  this 
  space 
  the 
  adiabatic 
  laws 
  

   prevail. 
  The 
  theodolite 
  measurements 
  give 
  the 
  height 
  of 
  the 
  

   top 
  of 
  the 
  cloud 
  where 
  the 
  process 
  of 
  saturation 
  ends. 
  The 
  

   saturated 
  or 
  yS 
  stage 
  has 
  two 
  cases 
  for 
  consideration, 
  the 
  first 
  

   being 
  where 
  the 
  top 
  of 
  the 
  cloud 
  is 
  lower 
  than 
  the 
  beginning 
  

   of 
  the 
  freezing 
  stage, 
  and 
  the 
  second 
  where 
  it 
  passes 
  into 
  or 
  

   through 
  that 
  stage. 
  We 
  computed 
  the 
  B'.t'.e'./i'. 
  at 
  the 
  top 
  of 
  

   the 
  cloud 
  in 
  the 
  first 
  case, 
  but 
  the 
  corresponding 
  B^.i^.e^./i^ 
  at 
  

   the 
  bottom 
  of 
  the 
  freezing 
  or 
  7 
  stage 
  in 
  the 
  second 
  case. 
  Then 
  

   the 
  thickness 
  of 
  the 
  7 
  stage 
  with 
  the 
  value 
  of 
  B°.t°.e°.h°. 
  at 
  

   the 
  top 
  of 
  it 
  followed, 
  these 
  being 
  the 
  same 
  as 
  B^^.t^^.e^^./i,/. 
  

   the 
  bottom 
  of 
  the 
  frozen 
  or 
  8 
  stage. 
  Finally 
  with 
  the 
  observed 
  

   h'\ 
  the 
  top 
  of 
  the 
  cloud, 
  B.'^t/^e 
  were 
  computed. 
  This 
  gives 
  

   the 
  heights 
  at 
  which 
  the 
  several 
  stages 
  begin 
  and 
  end, 
  and 
  

   hence 
  the 
  thickness 
  of 
  each 
  stage 
  ; 
  thence 
  the 
  gradients 
  of 
  

  

  