﻿FOGS 
  AND 
  CLOUDS 
  — 
  HUMPHREYS. 
  207 
  

  

  Scarf 
  cloud. 
  — 
  It 
  occasionally 
  happens 
  that 
  as 
  a 
  cumulus 
  rises 
  

   rapidly 
  to 
  a 
  great 
  height 
  a 
  thin 
  cirrus-like 
  cloud 
  arch, 
  convex 
  up- 
  

   ward, 
  forms 
  above, 
  and 
  detached 
  from, 
  the 
  topmost 
  cumulus 
  

   head 
  (pi. 
  21, 
  fig. 
  2), 
  so 
  suggestive 
  of 
  a 
  halo 
  as 
  to 
  arouse 
  poetic 
  if 
  not 
  

   even 
  pious 
  fancies. 
  As 
  the 
  cumulus 
  continues 
  to 
  rise 
  this 
  flossy 
  

   cloud 
  grows 
  and 
  rests 
  like 
  a 
  veil 
  over 
  the 
  thunderhead. 
  A 
  little 
  

   later, 
  a 
  few 
  minutes 
  at 
  most, 
  it 
  mantles 
  the 
  cumulus 
  shoulder 
  (pi. 
  

   22, 
  fig. 
  1), 
  the 
  head 
  or 
  heads 
  being 
  free, 
  and 
  may 
  even 
  drape 
  the 
  

   sides. 
  In 
  all 
  cases 
  it 
  has 
  the 
  sheen 
  and 
  apparent 
  texture 
  of 
  a 
  great 
  

   silken 
  scarf 
  — 
  hence 
  the 
  name. 
  It 
  has 
  often 
  been 
  called 
  false 
  cirrus, 
  

   but 
  that 
  term 
  is 
  now 
  commonly 
  restricted 
  to 
  an 
  entirely 
  different 
  

   cloud. 
  It 
  frequently 
  is 
  also 
  called 
  a 
  cap 
  cloud, 
  but 
  this 
  name, 
  apart 
  

   from 
  being 
  loosely 
  applied 
  to 
  anj^ 
  sort 
  of 
  cloud 
  on 
  a 
  mountain 
  peak, 
  

   is 
  applicable, 
  by 
  analogy, 
  only 
  during 
  the 
  early 
  stages 
  of 
  the 
  develop- 
  

   ment 
  of 
  the 
  scarf 
  cloud 
  and 
  hence 
  neither 
  distinctive 
  nor 
  properly 
  

   descriptive. 
  

  

  It 
  is 
  caused 
  by 
  the 
  rising 
  and 
  consequent 
  expansion 
  and 
  cooling 
  

   of 
  the 
  air 
  directly 
  above 
  the 
  cumulus 
  heads. 
  Ordinarily 
  this 
  move- 
  

   ment 
  and 
  cooling 
  of 
  the 
  air 
  over 
  the 
  cumulus 
  produces 
  no 
  visible 
  effect. 
  

   Occasionally, 
  however, 
  there 
  happens 
  to 
  be 
  a 
  stratum 
  of 
  air 
  at 
  a 
  con- 
  

   siderable 
  height 
  (3 
  or 
  4 
  miles) 
  that 
  is 
  practically 
  saturated. 
  When 
  

   such 
  a 
  layer 
  is 
  lifted 
  locally, 
  as 
  just 
  explained, 
  a 
  thin 
  cloud, 
  the 
  first 
  

   stage 
  of 
  the 
  scarf 
  cloud, 
  is 
  formed 
  at 
  the 
  place 
  of 
  disturbance. 
  When 
  

   this 
  layer 
  is 
  thin, 
  as 
  it 
  commonly 
  is, 
  the 
  thunderheads 
  generally 
  pass 
  

   quite 
  through 
  it 
  into 
  drier 
  air 
  above, 
  leaving 
  the 
  scarf 
  cloud 
  mantling 
  

   the 
  shoulders 
  of 
  the 
  cumulus, 
  or 
  draping 
  its 
  sides 
  at 
  about 
  the 
  original 
  

   level 
  of 
  the 
  humid 
  stratum. 
  

  

  Although 
  this 
  is 
  not 
  a 
  rare 
  cloud, 
  few, 
  apparently, 
  are 
  familiar 
  

   with 
  it, 
  owing 
  to 
  its 
  ephemeral 
  nature 
  and 
  occurrence 
  with 
  other 
  

   clouds. 
  It 
  has, 
  of 
  course, 
  but 
  little 
  of 
  the 
  grandeur 
  of 
  a 
  towering 
  

   cumulus 
  or 
  intricacy 
  of 
  a 
  far-flung 
  cirrus, 
  nevertheless, 
  its 
  coming 
  

   into 
  existence 
  at 
  an 
  unexpected 
  place, 
  its 
  silken 
  texture, 
  and 
  its 
  

   changes 
  in 
  form 
  and 
  position 
  all 
  merit 
  its 
  being 
  carefully 
  looked 
  for 
  

   and 
  closely 
  followed 
  when 
  found. 
  

  

  Tonitro-cirrus. 
  — 
  The 
  name 
  " 
  tonitro-cirrus," 
  thunder 
  cirrus, 
  is 
  ap- 
  

   plied 
  to 
  those 
  gray 
  locks, 
  to 
  speak 
  figuratively, 
  combed 
  out 
  from 
  old 
  

   thunderheads 
  by 
  the 
  upper 
  winds, 
  and 
  also 
  the 
  thinner 
  edges 
  of 
  the 
  

   anvil 
  cloud, 
  or 
  spreading 
  top 
  of 
  a 
  cumulo-nimbus. 
  (PL 
  22, 
  fig. 
  2.) 
  

  

  Even 
  though 
  the 
  winds 
  of 
  the 
  lower 
  atmosphere 
  are 
  always 
  light 
  

   when 
  great 
  towering 
  cumuli 
  are 
  formed, 
  the 
  upper 
  winds 
  may 
  still 
  

   be 
  strong. 
  Clearly, 
  then, 
  the 
  top 
  of 
  a 
  cumulus 
  that 
  extends 
  into 
  a 
  

   stratum 
  of 
  swift 
  winds 
  is 
  certain 
  to 
  be 
  drawn 
  out 
  into 
  a 
  more 
  or 
  

   less 
  extensive, 
  fibrous 
  sheet 
  of 
  snow 
  crystals 
  that 
  differs 
  but 
  little, 
  

   if 
  any, 
  from 
  the 
  ordinary 
  cirrus 
  except 
  in 
  its 
  mode 
  of 
  origin. 
  A 
  

   more 
  common 
  name 
  for 
  this 
  cloud 
  is 
  " 
  false 
  cirrus,' 
  but 
  this 
  term 
  

  

  