﻿FOGS 
  AND 
  CLOUDS 
  HUMPHREYS. 
  209 
  

  

  exquisite 
  beauty. 
  The 
  fundamental 
  pattern, 
  however 
  simple 
  or 
  

   complex 
  the 
  crystal, 
  is 
  always 
  the 
  same, 
  the 
  hexagon, 
  or 
  six-sided 
  

   column, 
  but 
  the 
  variety 
  is 
  endless: 
  Needles 
  with 
  pyramidal 
  ends; 
  col- 
  

   umns, 
  with 
  flat 
  ends; 
  mere 
  hexagonal 
  flakes; 
  hexagons 
  with 
  a 
  simple 
  

   extension 
  at 
  each 
  angle, 
  and 
  hexagons 
  with 
  complex 
  extensions 
  in 
  

   myriad 
  varieties 
  — 
  and 
  all 
  are 
  beautiful. 
  Naturally 
  then, 
  hundreds 
  of 
  

   these 
  numberless 
  forms, 
  as 
  admirably 
  photographed 
  by 
  that 
  en- 
  

   thusiast, 
  Mr. 
  W. 
  A. 
  Bentley, 
  of 
  Jericho, 
  Vt., 
  have 
  been 
  used 
  as 
  models 
  

   in 
  design 
  and 
  art. 
  Nor 
  is 
  there 
  a 
  keener 
  zest 
  than 
  Mr. 
  Bentley's 
  as 
  

   year 
  after 
  year 
  he 
  adds 
  pattern 
  upon 
  pattern 
  to 
  his 
  long 
  since 
  marvel- 
  

   ous 
  collection 
  of 
  photomicrographs 
  of 
  the 
  snow 
  crystal. 
  

  

  WHY 
  THE 
  ATMOSPHERE 
  AS 
  A 
  WHOLE 
  NEVER 
  IS 
  SATURATED. 
  

  

  Since 
  evaporation 
  is 
  continuous 
  from 
  much 
  the 
  greater 
  portion 
  

   of 
  the 
  surface 
  of 
  the 
  earth, 
  it 
  would 
  seem 
  that 
  the 
  atmosphere 
  would 
  

   soon 
  become 
  saturated 
  throughout, 
  and 
  perhaps 
  even 
  filled 
  every- 
  

   where 
  with 
  fog 
  and 
  cloud. 
  But 
  before 
  the 
  surface 
  air 
  has 
  become 
  

   approximately 
  saturated 
  to 
  any 
  considerable 
  depth 
  it 
  commonly 
  

   is 
  carried 
  to 
  higher 
  levels 
  by 
  some 
  type 
  of 
  convection, 
  and 
  this 
  causes 
  

   it 
  to 
  cool, 
  as 
  already 
  explained, 
  and 
  eventually 
  to 
  give 
  up 
  much 
  of 
  

   its 
  moisture, 
  generally 
  in 
  the 
  condition 
  of 
  rain 
  or 
  snow. 
  Sooner 
  or 
  

   later, 
  however, 
  the 
  air 
  out 
  of 
  which 
  the 
  precipitation 
  falls 
  returns 
  

   to 
  lower 
  levels 
  where 
  clearly 
  it 
  is 
  less 
  humid, 
  on 
  the 
  average, 
  than 
  

   when 
  it 
  began 
  to 
  ascend, 
  by 
  the 
  amount 
  of 
  water 
  abandoned 
  dur- 
  

   ing 
  its 
  upward 
  course. 
  In 
  short, 
  vertical 
  convection 
  induces 
  

   precipitation 
  through 
  cooling, 
  and 
  precipitation 
  in 
  turn 
  so 
  dries 
  the 
  

   air 
  as 
  to 
  prevent 
  it 
  from 
  becoming 
  and 
  remaining 
  everywhere 
  in- 
  

   tolerably 
  humid, 
  as 
  it 
  otherwise 
  would 
  be. 
  

  

  WHY 
  CLOUDS 
  FLOAT. 
  

  

  Since 
  water 
  is 
  about 
  800 
  times 
  heavier 
  than 
  air, 
  one 
  might 
  well 
  

   wonder 
  how 
  it 
  is 
  possible 
  for 
  a 
  cloud, 
  consisting 
  of 
  myriads 
  of 
  drop- 
  

   lets, 
  to 
  float 
  in 
  a 
  medium 
  so 
  light 
  and 
  of 
  such 
  slight 
  resistance 
  to 
  

   penetration 
  as 
  the 
  atmosphere. 
  But, 
  however 
  imperceptible 
  and 
  

   entirely 
  negligible 
  the 
  resistance 
  of 
  still 
  air 
  may 
  be 
  to 
  our 
  own 
  

   movements, 
  it 
  is 
  not 
  strictly 
  zero. 
  In 
  vacuo, 
  for 
  instance, 
  as 
  we 
  

   know 
  from 
  one 
  of 
  the 
  most 
  familiar 
  of 
  experiments, 
  " 
  the 
  farthing 
  

   and 
  the 
  feather 
  fall 
  together," 
  but 
  more 
  and 
  more 
  apart 
  in 
  air 
  of 
  

   increasing 
  density. 
  Now 
  the 
  total 
  pull 
  of 
  a 
  raindrop, 
  say, 
  causing 
  

   it 
  to 
  fall, 
  remains 
  the 
  same 
  no 
  matter 
  how 
  finely 
  it 
  is 
  divided, 
  while 
  

   the 
  amount 
  of 
  air 
  disturbed, 
  and 
  hence 
  the 
  resistance 
  and 
  time 
  of 
  

   fall, 
  increase 
  with 
  every 
  subdivision; 
  and 
  since 
  a 
  single 
  raindrop, 
  

   one-sixth 
  of 
  an 
  inch 
  in 
  diameter, 
  is 
  divisible 
  into, 
  or 
  is 
  the 
  equivalent 
  

   of, 
  8,000,000 
  average 
  cloud 
  droplets, 
  it 
  is 
  clear 
  that, 
  while 
  the 
  rain 
  

  

  